The phase transitions of 4-aminopyridine-based indolocarbazoles: twinning, local- and pseudo-symmetry

Kader, T.; Stöger, B.; Fröhlich, J.; Kautny, P.

doi:10.1107/S2052520618017341

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ISSN: 2052-5206

Volume 75| Part 1| February 2019| Pages 97-106

https://doi.org/10.1107/S2052520618017341

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The phase transitions of 4-aminopyridine-based indolocarbazoles: twinning, local- and pseudo-symmetry

Thomas Kader,^a Berthold Stöger,^b ^* Johannes Fröhlich ^a and Paul Kautny ^a

^aInstitute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria, and ^bX-Ray Centre, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria
^*Correspondence e-mail: bstoeger@mail.tuwien.ac.at

(Received 23 October 2018; accepted 7 December 2018; online 24 January 2019)

The phase transitions and polymorphism of three 4-aminopyridine-based indolocarbazole analogues are analyzed with respect to symmetry relationships and twinning. Seven polymorphs were structurally characterized using single-crystal diffraction. 5NICz (the indolo[3,2,1-jk]carbazole derivative with the C atom in the 5-position replaced by N) crystallizes as a P2₁/a high-temperature (270 K) polymorph and as a Pca2₁ low-temperature (150 K) polymorph. Even though their space-group symmetry is not related by a group–subgroup relationship, the local symmetries of both belong to the same order–disorder (OD) groupoid family. Both are polytypes of a maximum degree of order and are twinned by point operations of the other polytype. 2NICz (C atom in the 2-position replaced by N) likewise crystallizes in a high-temperature (Pcca, 280 K) polymorph and a low-temperature (P2₁/c, 150 K) polymorph. Here, the space-group symmetries are related by a group–subgroup relationship. The low-temperature phase is twinned by the point operations lost on cooling. The crystal structure of bulk 2,5NICz (N-substitution at the 2- and 5-positions) was unrelated to 2NICz and 5NICz and no phase transition was observed. Isolated single crystals of a different polymorph of 2,5NICz, isotypic with 2NICz, were isolated. However, the analogous phase transition in this case takes place at distinctly higher temperatures (> 300 K).

Keywords: phase transition; polymorphism; polytypism; twinning; order–disorder (OD) theory.

CCDC references: 1883688; 1883689; 1883690; 1883691; 1883692; 1883693; 1883694

1. Introduction

Symmetry relationships are crucial in understanding and describing phase transitions (Müller, 2013 ). In most cases of displacive phase transition (Tolédanoc et al., 2006 ), the symmetry of a high-temperature (HT) phase is a strict super group of the symmetry of the low-temperature (LT) phase (disregarding minor variations of cell parameters). Nevertheless, exceptions exist. For example, numerous incommensurate phases feature a lock-in phase transition to a periodic (and therefore higher-symmetry) LT structure on cooling (Cummins, 1990 ). In such a case, both phases are derived from a higher-symmetry prototype structure, which may exist at high temperatures or may be purely hypothetical.

Reconstructive phase transitions are generally not restricted by group–subgroup relationships because, as the name implies, a significant rearrangement of atoms or molecules takes place. There are intermediate cases of symmetry transformations, where modules (layers, rods) are preserved but are arranged differently. In such a case, an interpretation using local symmetry can be insightful.

In this context, we present the structural phase transitions of three 4-aminopyridine derivatives of indolo[3,2,1-jk]carbazole (ICz), whereby C atoms para to the N atom of ICz are replaced by an N atom. The IUPAC atom numbering-scheme is given in Fig. 1(a). The molecules under investigation, 5NICz, 2NICz and 2,5NICz feature substitution of C atoms by N at the respective positions [Figs. 1(b)–1(d)].

Figure 1
Schematics of (a) ICz with IUPAC numbering scheme and (b–d) the 4-aminopyridine derivatives 5NICz, 2NICz and 2,5NICz.

Crystals of 5NICz and 2NICz exist in distinct HT and LT polymorphs, which interconvert below room temperature. 2,5NICz exists in the solid state as three polymorphs. The bulk 2,5NICz-1 crystallizes in a structure unrelated to 5NICz and 2NICz. We could not find any evidence of a phase transition in the solid state for this polymorph. While attempting to obtain improved diffraction data, we found isolated crystals of a different polymorph, which is isostructural to 2NICz. These crystals featured an analogous phase transition (polymorphs designated 2,5NICz-2LT and 2,5NICz-2HT), though with a transition temperature above room temperature.

The observed phase transitions are analyzed with respect to symmetry relationships. Whereas the symmetries of 2NICz-LT and 2NICz-HT polymorphs (and the 2,5NICz-2LT and 2,5NICz-2HT polymorphs) can be described using classical group–subgroup relationships, the local symmetry has to be considered for 5NICz. For this purpose, we use the formalism developed in the framework of order–disorder (OD) theory (Dornberger-Schiff & Grell-Niemann, 1961 ; Ferraris et al., 2008 ). Despite being of the same name, this theory of polytypism is not related to order–disorder phase transitions. A summary of the phase transitions and the structural relationships between the seven polymorphs is schematized in Fig. 2.

Figure 2
Phase transition temperatures (red arrows) and structural relationships (black arrows) relating the seven polymorphs described in this work. The meaning of `same OD groupoid family' is explained at the end of §3.1.1

. Polymorphs not connected by arrows are structurally unrelated.

2. Experimental

2.1. Synthesis and crystal growth

The molecules under investigation were synthesized by ring closure of 9-(2-bromophenyl)-9H-carbazole derivatives with the appropriate N-substitution patterns using 5 mol% of an allyl[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]chloropalladium(II) catalyst. Reaction optimization studies and full characterizations are given by Kader et al. (2019 ). Crystals were grown by slow evaporation of acetonitrile solutions.

To prepare 5NICz, a glass vial was charged with 9-(3-bromopyridin-4-yl)-9H-carbazole (1 equiv., 324 mg, 1 mmol), K₂CO₃ (2 equiv., 276 mg, 2 mmol) and Pd catalyst (0.05 equiv., 29 mg, 0.05 mmol) and flushed with argon. After addition of 10 ml degassed N,N-dimethylacetamide, the reaction was stirred under argon atmosphere until full conversion. The cooled reaction mixture was poured into water and extracted into CH₂Cl₂. The organic phase was dried over Na₂SO₄ and concentrated under reduced pressure. The crude product was purified by column chromatography. 2NICz was prepared according to the same procedure starting from 5-(2-bromophenyl)-5H-pyrido[4,3-b]indole (1 equiv. 322 mg, 1 mmol). Column chromatography afforded fractions of pure 2NICz as well as mixtures of 2NICz and 5NICz. 2,5NICz was prepared according to the same procedure starting from 5-(3-bromopyridin-4-yl)-5H-pyrido[4,3-b]indole (1 equiv., 324 mg, 1 mmol). 5,11NICz was obtained as secondary product.

2.2. Data collection and refinement

2.2.1. General

Intensity data were collected in a dry stream of nitrogen on a Bruker Kappa APEX II diffractometer system using graphite-monochromated Mo K $[{{\overline{\alpha}}}]$ radiation. Data were reduced to intensity values using SAINT (Bruker, 2017 ). Corrections for absorption and related effects were applied using SADABS (Bruker, 2017). The structures were solved with SHELXT (Sheldrick, 2015a ) and refined with SHELXL (Sheldrick, 2015b ). The atoms were labelled according to IUPAC rules (Fig. 1a). In the case of two crystallographically different molecules (Z′ = 2), prime characters are added for the second molecule. For molecules located on twofold axes, atoms pairs that are equivalent by symmetry are assigned the lower out of the two possible numbers. More data collection and refinement details are summarized in Tables 1 and 2, and described in the following sections.

Table 1
Experimental details

For all structures: colourless crystals, Mo Kα radiation, Bruker Kappa APEX II CCD diffractometer, multi-scan absorption correction, H-atom parameters constrained.

	5NICz-LT	5NICz-HT	2NICz-LT	2NICz-HT
Crystal data
Chemical formula	C₁₇H₁₀N₂	C₁₇H₁₀N₂	C₁₇H₁₀N₂	C₁₇H₁₀N₂
M_r	242.27	242.27	242.27	242.27
Crystal system, space group	Orthorhombic, Pca2₁	Monoclinic, P2₁/a	Monoclinic, P2₁/c	Orthorhombic, Pccn
Temperature (K)	150	270	150	280
a, b, c (Å)	7.394 (9), 10.953 (13), 29.06 (3)	8.2204 (15), 10.898 (2), 26.905 (5)	4.064 (8), 16.58 (3), 17.57 (3)	4.1239 (8), 16.404 (3), 17.252 (3)
α, β, γ (°)	90, 90, 90	90, 98.691 (4), 90	90, 91.53 (5), 90	90, 90, 90
V (Å³)	2353 (5)	2382.6 (8)	1184 (4)	1167.1 (4)
Z	8	8	4	4
μ (mm⁻¹)	0.08	0.08	0.08	0.08
Crystal shape	Rod	Rod	Rod	Rod
Crystal size (mm)	0.55 × 0.16 × 0.10	0.55 × 0.16 × 0.10	0.55 × 0.08 × 0.04	0.30 × 0.10 × 0.06

Data collection
T_min, T_max	0.552, 0.745	0.600, 0.746	0.549, 0.746	0.569, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	11 809, 3757, 2598	36 052, 5710, 3042	10 904, 2763, 1908	12 863, 1407, 778
R_int	0.075	0.077	0.063	0.061

Refinement
R[F² > 2σ(F²)]	0.098	0.091	0.055	0.043
wR[F² > 2σ(F²)]	0.242	0.223	0.110	0.093
R(all)	0.134	0.168	0.098	0.099
wR(all)	0.276	0.280	0.128	0.119
S	1.03	1.06	1.02	1.00
No. of reflections	3757	5710	2763	1407
No. of parameters	343	344	173	88
No. of restraints	1	0	0	0
Δρ_max, Δρ_min (e Å⁻³)	0.65, −0.33	0.50, −0.30	0.20, −0.27	0.17, −0.18
Absolute structure	?†	–	–	–
Absolute structure parameter	?†	–	–	–
Twin operation	$[\bar 1]$	2_[100]	2_[100]	–
Volume fraction (%)	?†	53.9: 46.1 (3)	53.3: 46.7 (3)	–

	2,5NICz-1	2,5NICz-2LT	2NICz-2HT
Crystal data
Chemical formula	C₁₆H₉N₃	C₁₆H₉N₃	C₁₆H₉N₃
M_r	243.26	243.26	243.26
Crystal system, space group	Orthorhombic, Pmn2₁	Monoclinic, P2₁/c	Orthorhombic, Pccn
Temperature (K)	100	300	380
a, b, c (Å)	19.316 (4), 3.7013 (8), 7.7676 (18)	4.0049 (13), 16.518 (5), 17.179 (5)	4.0741 (8), 16.416 (3), 17.230 (3)
α, β, γ (°)	90, 90, 90	90, 90.007 (10), 90	90, 90, 90
V (Å³)	555.3 (2)	1136.5 (6)	1152.3 (4)
Z	2	4	4
μ (mm⁻¹)	0.09	0.09	0.09
Crystal shape	Plate	Plate	Plate
Crystal size (mm)	0.45 × 0.23 × 0.03	0.32 × 0.10 × 0.02	0.32 × 0.10 × 0.02

Data collection
T_min, T_max	0.424, 0.493	0.513, 0.745	0.609, 0.745
No. of measured, independent and observed [I > 2σ(I)] reflections	5744, 1608, 1458	8439, 2027, 997	2369, 971, 393
R_int	0.034	0.088	0.056

Refinement
R[F² > 2σ(F²)]	0.041	0.053	0.050
wR[F² > 2σ(F²)]	0.100	0.106	0.108
R(all)	0.045	0.150	0.158
wR(all)	0.104	0.147	0.152
S	1.07	0.96	0.93
No. of reflections	1608	2027	971
No. of parameters	91	174	88
No. of restraints	1	0	0
Δρ_max, Δρ_min (e Å⁻³)	0.33, −0.27	0.25, −0.23	0.13, −0.18
Absolute structure	Flack x determined using 561 quotients [(I+)−(I−)]/[(I+)+(I−)] (Parsons et al., 2013 )	–	–
Absolute structure parameter	−0.3 (10)	–	–
Twin operation	?†	2_[100]	–
Volume fraction (%)	?†	54.7:45.3 (4)	–
Computer programs: SAINT, APEXII, SADABS (Bruker, 2017), SHELXL2014/7 (Sheldrick, 2015b).

†Not determined owing to a lack of significant resonant scatterers.

Table 2
Non-classical C—H⋯N hydrogen bonding in both polymorphs of 5NICz

D—H⋯A	D—H (Å)	H⋯A (Å)	D⋯A (Å)	D—H⋯A (°)
150 K
C7—H⋯N5′	0.95	2.47	3.389 (14)	162.7
C9—H⋯N5′	0.95	2.80	3.722 (14)	163.2
C7′—H⋯N5	0.95	2.51	3.426 (14)	160.7
C9′—H⋯N5	0.95	2.78	3.706 (15)	163.8
270 K
C7—H⋯N5	0.93	2.53	3.446 (9)	167.0
C9—H⋯N5	0.93	2.86	3.784 (9)	173.8
C7′—H⋯N5′	0.93	2.50	3.404 (5)	165.0
C9′—H⋯N5′	0.93	2.87	3.789 (7)	172.1

2.2.2. Details for 5NICz

Crystals of 5NICz were small, yet of reasonable quality according to optical microscopy. Nevertheless, in preliminary scans at the routine temperature of 150 K, all plates featured mediocre reflection quality and diffracted only to small 2θ angles. Such a bad diffraction quality for optically flawless crystals can be a sign of a reconstructive phase transition on cooling. Indeed, crystals cooled to 150 K showed clear signs of fracturing. Two data sets were, therefore, collected with long exposure times, one above the phase transition temperature at 270 K and one after slow cooling to 150 K. To our surprise, even at 270 K the reflection quality was not significantly improved.

For the 150 K data set a reasonable structure solution and refinement, considering the mediocre diffraction quality, was possible in the space group Pca2₁.

The 270 K phase had apparent orthorhombic C-centred (oC) metrics. But, since a sensible structure solution was not possible in this setting and slight splitting of reflections indicated a lower metric symmetry, the data were reprocessed in the corresponding monoclinic primitive (mP) setting. Structure solutions and refinements were performed in the space group P2₁/a under consideration of twinning by pseudo-merohedry. The non-standard setting of the space group P2₁/c was chosen to ease comparison with the LT polymorph.

2.2.3. Details for 2NICz, 2,5NICz-2LT and 2,5NICz-2HT

The cell parameters of the LT-polymorph of 2NICz were apparently orthorhombic primitive (oP) and, therefore, data were at first processed assuming such a symmetry. A structure solution was successful in the space group Pccn. But all attempts at refinements resulted in excessively anisotropic atomic displacement parameters (ADPs) and mediocre residuals. Since, in analogy to 5NICz, reflections at higher diffraction angles were split, an attempt was made in the P2₁/c space group under consideration of twinning by pseudo-merohedry. The ADPs as well as the residuals improved significantly (R_obs > 10% to ∼5.5%). For the HT phase, on the other hand, a refinement using Pccn symmetry was successful. In this case, reducing the symmetry to monoclinic did not improve reliability factors.

The cell parameters of 2,5NICz-2 L T suggested a structure isostructural to 2NICz. Refinements were, therefore, performed using starting models derived from the 2NICz model. Even at 300 K, refinements in the LT P2₁/c model resulted in significantly improved residuals (R_obs > 10% to ∼5.3%), even though the metrics are orthorhombic within the estimated standard errors. Only when heating to 380 K was the Pccn HT phase clearly observed. In 2,5NICz-2HT, the molecules are located on a twofold axis and the N5 atom is accordingly positionally disordered with the C11 atom in a 1:1 manner. In 2,5NICz-2LT, this position splits in two and both positions were refined as positionally disordered, by constraining the sum of the N-occupancies of both positions to 1. Ultimately, the N-occupancy of one position refined 0.58 (4) (the other accordingly being constrained to 0.42).

2.2.4. Details for 2,5NICz-1

The structure of 2,5NICz-1 was determined by routine refinement. The 2,5NICz molecule is located on a twofold axis and, therefore, the N5 and C11 atoms are positionally disordered in a 1:1 manner.

2.3. X-ray powder diffraction

Low-temperature X-ray powder diffraction (XRPD) experiments were performed on a Panalytical X'Pert Pro diffractometer equipped with an Oxford Cryosystems PheniX closed cycle cryostat in Bragg–Brentano geometry using Cu Kα_1,2 radiation (λ = 1.540598, 1.544426 Å) with an Ni filter and an X'celerator multi-channel detector. The ground bulk sample was placed on an Si single crystal cut along the (711) plane. Scans were recorded in vacuum in the $[2\theta = 10]$ –70° range in 10 K steps from 300 K to 100 K and back to 300 K with heating and cooling rates of 1 K min⁻¹ and 5 min isothermals between scans.

3. Results and discussion

3.1. The OD polytypism of 5NICz

3.1.1. Local symmetry

The HT and LT phases of 5NICz are structurally closely related. They crystallize in the P12₁/a1 and Pca2₁ symmetry, respectively and contain Z′ = 2 5NICz molecules in the asymmetric unit. The structures can be considered as being composed of A_n layers (n is a sequential integer) extending parallel to (001) (Fig. 3). These layers are made up of rods of molecules which connect via short C—H⋯N contacts (Fig. 4). Whereas these rods are very similar in both structures (differences will be discussed below), their inclination with respect to the layer plane (001) differs significantly (Fig. 3). The angles of the least-squares planes of the molecules to the (001) plane are 67.5° and 67.6° versus 55.7° and 56.5° for the LT and HT phases, respectively. Thus, the two kinds of layers can be derived from each other, but they might not be considered as isostructural (Kálmán et al., 1993 ) in the strict sense.

Figure 3
The (a,b) LT and (c,d) HT polymorphs of 5NICz viewed down (a,c) [100] and (b,d) [010]. Molecules are coloured according to space-group symmetry equivalence. H atoms are omitted for clarity. Layer names are indicated to the right. Crystallographic symmetry elements are indicated by the common graphical symbols (Hahn & Aroyo, 2016

Figure 4
Rods of 5NICz molecules connected by C—H⋯N interactions (dotted lines) extending along [010] in the (a) LT and (b,c) HT polymorphs. Note that in the HT polymorph there are two kinds of rods, whereas in the LT polymorph all rods are related by symmetry. C and N atoms are represented by grey and blue ellipsoids, respectively, drawn at the 50% probability levels, H atoms by white spheres of arbitrary radius. Pseudo (a) and crystallographic (b,c) 2₁ screw axes are indicated using the usual symbol (Hahn & Aroyo, 2016

Adjacent molecules in the rods described above are related by a 2₁ operation in the [010] direction. The operation is exact in the HT phase (one crystallographically unique molecule per rod) but only approximate in the LT phase (two molecules per rod). Adjacent rods are, in both polymorphs, related by an a operation in the [010] direction. Moreover, they are related by inversions, which is a space group operation in the HT and a local operation in the LT phase. Thus, the layers possess P12₁/a(1) actual (HT) or pseudo (LT) symmetry. Since we will perform an interpretation according to the OD theory, here we use the OD notation of layer symmetry, whereby parentheses indicate the direction lacking translational symmetry (Dornberger-Schiff & Grell-Niemann, 1961). In the LT polymorph, adjacent A_n layers are related by actual 2₁ screw rotations in [001] and c glide reflections in [100] direction, whereas in the HT polymorph, these are only a pseudo-symmetry operations. In total, both polymorphs are made up of Z′ = 2 crystallographically different molecules.

Recognizing the pseudo-symmetry of layers is the key to an OD interpretation. By assuming the pseudo-symmetry to be exact, both polymorphs can be described as members of OD families. The symmetries of OD families are classified into OD groupoid families, which correspond to space group types in classical crystallography (Fichtner, 1979a ). The symmetries of both polymorphs belong to the same OD groupoid family, which is described by

$[\matrix{P &1 &2_{1}/a &(1)\cr \{ &2_{r-1}/n_{s-1,2}& - &(2_{2}/n_{r,s})&\}}]$

according to the notation of Dornberger-Schiff & Grell-Niemann (1961). The metric parameter s adopts the value s = 1 in both cases, which can be expressed by

$[\matrix{P &1 &2_{1}/a &(1) \cr \{ &2_{r-1}/c_{2} &- &(2_{2}/n_{r,1})&\}}.]$

OD groupoids are made up of partial operations (POs), which relate layers but need not apply to the whole stacking sequence. The first line in these symbols gives the symmetry group of the layers [the λ-POs, here P12₁/a(1)]. The second line lists one possible set of operations relating adjacent layers (σ-POs). Since the relative intrinsic translations of the σ-POs are not restricted to those found in space groups, generalized Hermann–Mauguin symbols are used. For example, the n_r,s glide reflection in the symbol above has the glide vector $[r{\bf a}/2+s{\bf b}/2]$ . As can be seen in Fig. 3, the x-component of the glide vector is approximately $[{{1} \over {4}}]$ and thus $[r\approx{{1} \over {2}}]$ (§3.1.5).

Intrinsic translation components in the stacking direction [001] are given with respect to the vector $[{\bf c}_{0}]$ , which is perpendicular to the layers and of the length of one layer width. Thus, the 2₂ operation in [001] direction has the screw vector $[{\bf c}_{0}]$ (Fichtner, 1979b ) since n_m stands for an n-fold screw rotation with intrinsic translation of $[{{m} \over {n}}]$ parts of the shortest lattice vector in the translation direction.

3.1.2. Stacking possibilities

The crucial aspect of OD structures is their ability of crystallizing in different polytypes, which are all locally equivalent (more precisely: pairs of adjacent layers are equivalent). If interactions beyond one layer width and deviations from the prototype layers are neglected, all polytypes can therefore be considered as energetically equivalent. The NFZ relationship (Ďurovič, 1997 ) is used to derive these stacking possibilities. For 5NICz, there are σ-POs that invert the orientation with respect to the stacking direction (σ-ρ-POs). But owing to $[r \,\notin \, \bb{Z}]$ none of these is a reverse continuation, which would mean that it maps A_n on A_n+1 and vice versa. In such a case, the NFZ relationship reads as $[Z = 2N/F = 2[{\cal G}_{n}:{\cal G}_{n}\cap{\cal G}_{{n+1}}]]$ , where Z is the number of positions A_n+1 can adopt given A_n and $[{\cal G}_{n}]$ is the group of those A_n operations that do not invert the orientation with respect to the stacking direction (λ-τ-POs).

Since s = 1, the a glide planes of all A_n overlap and $[{\cal G}_{n} = {\cal G}_{n}\cap{\cal G}_{{n+1}} = P1a(1)]$ . Accordingly, there are Z = 2[P1a(1):P1a(1)] = 2 ways of placing A_n+1 given A_n. These two possibilities are obtained by applying a 2_r-1 or a 2_1-r σ-PO on A_n, respectively.

3.1.3. Maximum degree of order (MDO) polytypes

Out of the infinity of stacking arrangements, two are of a MDO, which means that they cannot be decomposed into fragments of simpler polytypes (Dornberger-Schiff, 1982 ). MDO₁ [P2₁/a, $[{\bf c} = (r-1){\bf a}+2{\bf c}_{0}]$ ] is generated by repeated application of 2_r-1 σ-POs; MDO₂ [Pca2₁, $[{\bf c} = 2{\bf c}_{0}]$ ] by alternating application of 2_r-1 and 2_1-r σ-POs. The local symmetry of both polytypes is schematized in Fig. 5.

Figure 5
Symmetry of the MDO₁ and MDO₂ polytypes of 5NICz viewed along b. Molecules are represented by bars which are red on one side and blue on the other. Darker colours indicate translation by b/2. λ-POs of the layers and σ-POs relating adjacent layers are indicated by the common graphical symbols (Hahn & Aroyo, 2016

) and, in the case of unusual intrinsic translations, by their printed symbols. Symbols of POs that are valid for the whole polytype are red. The unit cell of the polytypes is marked by a grey backdrop.

In our experience, the overwhelming number of polytypes characterized by single-crystal diffraction is of the MDO kind. Other stacking arrangements may exist at domain interfaces. Indeed, the HT and LT polymorphs of 5NICz are precisely of the MDO₁ and MDO₂ type, respectively. Thus, even though the space groups of the two phases are not related by a group–subgroup relationship, their groupoids belong to the same groupoid family with the same restrictions on the metric parameters, viz. s = 1. Their local symmetries are therefore, in a sense, isomorphic, which demonstrates the usefulness of such a symmetry description.

3.1.4. Twinning

Crystals of OD polytypes are often twinned owing to stacking faults. The possible orientation states of the polytype are derived by coset decomposition of the point group of the polytype in the point group of the OD groupoid family, that is the point group generated by the linear parts of all POs of a polytype. This group is mmm for the OD groupoid family of the 5NICz polymorphs.

Thus, MDO₁ (HT) can appear in [mmm:12/m1] = 2 orientations, which are related by the operations of the twin law { 2_x,m_x,2_z,m_z}. This corresponds precisely to the observed twinning. MDO₂ (LT) can appear likewise in [mmm:mm2] = 2 orientations. In this case, the twin law is $[\{\overline{1},2_{x},2_{y},m_{z}\}]$ . Since the 5NICz molecules possess no significant resonant scatterers under Mo Kα radiation, this twinning by inversion could not be seen from the diffraction data. Its existence is nevertheless nearly certain. Besides being predicted by OD theory, it is also expected owing to the phase transition from the centro-symmetric MDO₁ (HT) phase. Point operations lost on phase transformation are typically retained as twin operations.

3.1.5. Desymmetrization and metric parameters

An important step in assessing an OD model is the quantification of the desymmetrization (Ďurovič, 1979 ) compared to the ideal model. Such a desymmetrization is expected (these geometrical differences may stabilize the individual polytypes) but should not be unreasonably large.

In the MDO₁ (HT) polytype, the symmetry of the actual A_n layers is identical to those of the idealized description [P12₁/a(1)]. According to the P2₁/a symmetry of the polytypes, the layers are partitioned into two equivalence classes, viz. the A_2n and the A_2n+1 layers. To evaluate the desymmetrization, the A₁ layer was mapped onto the A₀ layer by translation of $[-{\bf c}/2]$ and reflection at the r·a = 0 plane. The discrepancies between both layers are minute (max: C2/C2′, 0.157 Å), proving the validity of the pseudo-symmetry analysis.

In the MDO₂ (LT) polytype all layers are related by the Pca2₁ space group symmetry, but the symmetry of the layers is reduced by an index of 2 to P1a(1). To assess the degree of desymmetrization, the location of the pseudo-2₁ screw axis was determined by averaging the x- and z-coordinates of the non-H atoms of the two crystallographically independent molecules. The screw rotation was then applied to a layer. Here, the desymmetrization is even less pronounced than in the HT phase (max: C11/C11′, 0.086 Å).

The metric parameter r of the OD groupoids can be derived in the case of MDO₁ (HT) directly from the cell parameters as $[r = c\cos\beta/a+1 = 0.505]$ . Owing to r ≈ 1/2, the lattice symmetry of MDO₁ is pseudo-oC and the twinning is by pseudo-merohedry (the reflections of both domains are nearly coincident). More precisely, the twin obliquity calculates from the cell parameters as $[\omega = \tan^{{-1}}[a(r-{{1} \over {2}})/c/\sin\beta]\approx 0.1^{\circ}]$ . It has to be noted though that the derivation of the cell parameters from single-crystal data is inexact in such a case because overlapping reflections are treated as single reflections during integration. The deviation from r = 1/2 might, therefore, be larger than estimated here.

For MDO₂ (LT), r is derived from the x-coordinate of the pseudo-2₁ operation (see above) as r = 4x = 0.449. Thus, in both cases, despite the distinctly different orientation of the molecules, the parameter r is approximately 1/2.

3.1.6. Structural changes on phase transition

Even though symmetry considerations are the main focus of this work, changes at the crystallo-chemical level must not be neglected. As has been noted above, the structures of both 5NICz polymorphs are controlled by non-classical C—H⋯N hydrogen interactions, forming chains extending in the [010] direction (Fig. 4). Each molecule forms a pocket delimited by N8 and the H7 and H9 are in meta position to N8. These two H atoms are expected to be the most `acidic' and indeed interact with the N5 lone pair of the adjacent molecule. The hydrogen bonding is distinctly asymmetric with one short (C7⋯N5) and one long (C9⋯N5) interaction (Table 2).

The C⋯N distances are slightly longer in the HT phase. In return, the C—H⋯N angles are closer to linear, owing to near coplanarity of the connected molecules [Fig. 3(d)]. Overall, the hydrogen bonding can be considered as close to equivalent in both polymorphs.

Adjacent rods are connected by π–π interactions to layers. Here, the structural changes on phase transition are significant owing to a change in molecule inclination with respect to the layer plane (Fig. 6). The C—H⋯π contacts relating adjacent layers are, like the hydrogen bonding, very similar in both polymorphs. In summary, the dominant factor in the phase transition seems to be the π–π stacking.

Figure 6
Pairs of 5NICz molecules connected by π–π interactions in the (a,b) LT and (c,d) HT polymorphs, projected on the molecular plane. Atom colours of the top molecules as in Fig. 4

; bottom molecules in red for clarity. Ellipsoids are drawn at the 50% probability levels.

3.2. Phase transitions of 2NICz, and 2,5NICz-2LT and 2,5NICz-2HT polymorphs

3.2.1. Symmetry relationships

The 2LT and 2HT polymorphs of 2,5NICz are isostructural to the corresponding LT and HT 2NICz polymorphs, whereby the N5 and C11 atoms are positionally disordered. In contrast to 5NICz, the symmetries of the respective HT and LT polymorphs are related by a group–subgroup relationship. As is often observed in such a case, the symmetry of the HT phase (P2₁ / c 2₁ /c 2/ n, Z = 4) is a strict super group (here minimal) of the symmetry of the LT phase (P12₁ / c1, Z = 4).

The structures are again built up of rods of 2NICz (2,5NICz) molecules connected by short C—H⋯N interactions extending along [001] (Fig. 7). In the HT phase, the molecules are located on a twofold rotation axis and adjacent molecules are related by c_[100] and c_[010] glide reflections. The rods, therefore, possess $[{\scr p}cc2]$ symmetry (Kopsky & Litvin, 2006 ). In the [100] direction, adjacent rods are generated by lattice translations. From a thus constructed layer, the final structure with Pccn symmetry is generated by 2₁ screw rotations in the [010] direction.

Figure 7
Crystal structures of the (a,b) LT and (c,d) HT polymorphs of 2NICz viewed down (a,c) [100] and (b,d) [001]. Atom colours as in Fig. 4

. The 2LT and 2HT polymorphs of 2,5NICz are isostructural and not shown. Ellipsoids are drawn at the 50% probability levels. Crystallographic symmetry elements are indicated by the common graphical symbols (Hahn & Aroyo, 2016

In the LT phase, the twofold rotation symmetry of the rods is lost. Of the two c-glide reflections, only the operation with plane parallel to (010) is retained. Thus, the symmetry of the rods is reduced by an index of 2 from $[{\scr p}cc2]$ to $[{\scr p}1c1]$ . The rods are again related by translations forming layers parallel to (010) and the whole structure then generated by 2₁ screw rotations in [010] direction, resulting in an overall P2₁/c symmetry.

3.2.2. Twinning

Whereas the HT polymorphs are not twinned, on cooling below the phase transition temperature, the lost point operations are retained as twin operations. The twin law is obtained as a coset of the coset decomposition of the LT in the HT point group. Thus, the LT twin consists of [mmm:2/m] = 2 domains, whose orientations are related by the operations { 2_x,m_x,2_z,m_z}. The twinning is by pseudo-merohedry, since the orthorhombic metrics of the lattice are approximately retained. The twin obliquity is derived from the cell parameters as 1.5° (2NICz-LT) and 0.0° (2,5NICz-2LT). Indeed, for 2,5NICz-2LT no splitting of reflections was observed in single-crystal experiments, whereas for 2NICz-LT the twin obliquity is reflected in rows of diverging reflections.

3.2.3. Desymmetrization

The deviation of β from ideal orthorhombic metrics is a measure of desymmetrization. For a finer evaluation of the desymmetrization, the atomic coordinates were transformed in an orthonormal coordinate system and the pseudo-rotation axis located at $[({1\over 4},{1\over 4} ,z)]$ was applied to a molecule. The atoms in the original and the transformed molecule are separated by 0.52–0.68 Å (2NICz-LT) and 0.08–0.53 Å (2,5NICz-2LT). Whereas in 2NICz-LT the deviation is mostly due to a translation away from the rotation axis, in 2,5NICz-2LT the molecules are tilted with respect to the rotation axis of the HT phase (Fig. 8).

Figure 8
Overlay of molecules and their images by twofold rotation about the ( $[{1\over 4}, {1\over 4}, z]$ ) axis in the (a,b) 2NICz-LT and (c,d) 2,5NICz-2LT polymorphs viewed down (a,c) [100] and (b,d) [001]. The rotation axis is shown in green.

3.2.4. Crystal chemistry

As in the case of 5NICz, the central crystallo-chemical feature are rods connected by non-classical C—H⋯N hydrogen bonding involving the two H7 and H9 positions. Here, the bonding is more symmetrical, with two equivalent (HT) or only slightly different (by ca 0.05 Å; LT) bonds (Table 3). Enlarged ADPs of the N2 atom (Fig. 7c) indicate that the desymmetrization is dynamic, i.e. the orientations of the molecules oscillate between the two possible asymmetric states. Since the remaining structural changes are likewise minute, one can assume that the desymmetrization of the hydrogen-bonding is the decisive factor in the phase transition. Numerous reported solid–solid phase transitions are due to such a dynamic desymmetrization, a classical example being the KH₂PO₄ (KDP) family of ferroelectrics (Peercy, 1975 ).

Table 3
Non-classical C—H⋯N hydrogen bonding in the HT and LT polymorphs of 2NICz and the 2HT and 2LT polymorphs of 2,5NICz

D—H⋯A	D—H (Å)	H⋯A (Å)	D⋯A (Å)	D—H⋯A (°)
2NICz-LT
C7—H7⋯N2	0.95	2.59	3.540 (6)	174.5
C9—H9⋯N2	0.95	2.65	3.594 (6)	174.7
2NICz-HT
C7—H7⋯N2 (2×)	0.93	2.60	3.532 (2)	175.6
2,5NICz-2LT
C7—H7⋯N2	0.93	2.58	3.505 (6)	177.7
C9—H9⋯N2	0.93	2.60	3.529 (6)	175.5
2,5NICz-2HT
C7—H7⋯N2 (2×)	0.93	2.61	3.538 (5)	175.7

3.3. 2,5NICz-1

The bulk polymorph 2,5NICz-1 features a crystallographically non-challenging structure with Pmn2₁ symmetry. In analogy to the other structures presented here, the 2,5NICz molecules are connected by hydrogen bonds to chains (Fig. 9). In contrast to the 2,5NICz-2LT and 2,5NICz-2HT polymorphs, the connected molecules are coplanar (related by a b + c lattice translation), demonstrating that the inclination is determined by packing effects.

Figure 9
The crystal structure of 2,5NICz-1 viewed down [010]. Atom colours as in Fig. 4.

3.4. Powder diffraction

To determine the stability ranges of the LT and HT polymorphs and to rule out additional phase transitions, powdered samples of 5NICz and 2NICz were subjected to low-temperature powder diffraction (Fig. 10). In a bulk sample of 2,5NICz only the orthorhombic polymorph 1 could be seen by X-ray diffraction, which does not possess a phase transition in the solid state. Thus, in this case the exact phase transition temperature could not be determined. In both cases, 5NICz and 2NICz, the HT $[\leftrightarrow]$ LT transitions are clearly showed by appearance/vanishing of peaks and a distinct hysteresis of ∼20 K is observed [5NICz: transitions at 180–170 K (cooling) versus 200–210 K (heating); 2NICz: 210–200 K (cooling) versus 230–240 K (heating)]. No other phase transitions are apparent. The hysteresis suggests a phase transition of the first order. Even though neither powder diffraction nor DSC data for the 2,5NICz-2 polymorph could be acquired, experiments on the single crystal showed a smooth transition to the orthorhombic phase. This phase transition might be, therefore, of the second order.

Figure 10
Low-temperature XRPD scans of 5NICz (a,b) and 2NICz (c,d) over the 2θ range 10–30° on heating (a,c) and cooling (b,d) shown as heat maps. Maximum and minimum intensities are yellow and black, respectively.

4. Conclusion

From a crystallo-chemical point of view, the polymorphs of 5NICz, 2NICz and 2,5NICz are all closely related. Their structures are determined by non-classical C—H⋯N hydrogen bonding. The molecular orientations in the thus-formed rods differ owing to either N-substitution at different rings or with respect to the rotation of adjacent molecules.

Nevertheless, they are fundamentally different from a crystallographical point of view. The transitions between 2NICz-LT and 2NICz-HT, and the isostructural 2,5NICz-2LT and 2,5NICz-2HT are clearly displacive and, as expected in such a case, the symmetries of the polymorphs are related by a group–subgroup relationship. The transition of 5NICz, on the other hand, is a borderline case between displacive and reconstructive, with layers that are in principle similar but feature distinctly changed inclination of the molecules. More interestingly, the symmetry relationship between both polymorphs can only be understood by analysis of their space groupoids in the sense of OD theory. Thus, it is shown that a unified theory of local symmetry is needed.

Supporting information

CCDC references: 1883688; 1883689; 1883690; 1883691; 1883692; 1883693; 1883694

Crystal structure: contains datablocks global, 2NICz-LT, 2NICz-HT, 5NICz-LT, 5NICz-HT, 25NICz-1, 25NICz-2LT, 2NICz-2HT. DOI: https://doi.org/10.1107/S2052520618017341/wf5145sup1.cif

Structure factors: contains datablock 2NICz-LT. DOI: https://doi.org/10.1107/S2052520618017341/wf51452NICz-LTsup2.hkl

Structure factors: contains datablock 2NICz-HT. DOI: https://doi.org/10.1107/S2052520618017341/wf51452NICz-HTsup3.hkl

Structure factors: contains datablock 5NICz-LT. DOI: https://doi.org/10.1107/S2052520618017341/wf51455NICz-LTsup4.hkl

Structure factors: contains datablock 5NICz-HT. DOI: https://doi.org/10.1107/S2052520618017341/wf51455NICz-HTsup5.hkl

Structure factors: contains datablock 25NICz-1. DOI: https://doi.org/10.1107/S2052520618017341/wf514525NICz-1sup6.hkl

Structure factors: contains datablock 25NICz-2LT. DOI: https://doi.org/10.1107/S2052520618017341/wf514525NICz-2LTsup7.hkl

Structure factors: contains datablock 2NICz-2HT. DOI: https://doi.org/10.1107/S2052520618017341/wf51452NICz-2HTsup8.hkl

Computing details top

For all structures, program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2014).

(2NICz-LT) top

Crystal data top

C₁₇H₁₀N₂	F(000) = 504
M_r = 242.27	D_x = 1.360 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 4.064 (8) Å	Cell parameters from 1692 reflections
b = 16.58 (3) Å	θ = 2.6–24.3°
c = 17.57 (3) Å	µ = 0.08 mm⁻¹
β = 91.53 (5)°	T = 150 K
V = 1184 (4) Å³	Rod, colourless
Z = 4	0.55 × 0.08 × 0.04 mm

Data collection top

Bruker KAPPA APEX II CCD diffractometer	1908 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.063
ω– and φ–scans	θ_max = 27.9°, θ_min = 1.2°
Absorption correction: multi-scan SADABS	h = −5→5
T_min = 0.549, T_max = 0.746	k = −21→21
10904 measured reflections	l = −22→22
2763 independent reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.055	H-atom parameters constrained
wR(F²) = 0.128	w = 1/[σ²(F_o²) + (0.0477P)² + 0.2046P] where P = (F_o² + 2F_c²)/3
S = 1.02	(Δ/σ)_max < 0.001
2763 reflections	Δρ_max = 0.20 e Å⁻³
173 parameters	Δρ_min = −0.27 e Å⁻³

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refined as a 2-component inversion twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
N2	0.7416 (10)	0.23658 (13)	0.36549 (10)	0.0341 (6)
N8	0.7519 (8)	0.24803 (12)	0.59699 (8)	0.0237 (4)
C1	0.8947 (9)	0.29941 (15)	0.40130 (14)	0.0319 (8)
H1	0.9959	0.3397	0.3715	0.038*
C3	0.5911 (9)	0.17722 (16)	0.40626 (13)	0.0307 (7)
H3	0.4854	0.1342	0.3795	0.037*
C4	0.2985 (8)	0.06311 (14)	0.56817 (13)	0.0298 (7)
H4	0.2298	0.0309	0.5260	0.036*
C3A	0.5877 (8)	0.17767 (14)	0.48767 (13)	0.0242 (7)
C3B	0.4733 (7)	0.13457 (13)	0.55673 (13)	0.0237 (6)
C3C	0.7506 (11)	0.24419 (15)	0.51806 (10)	0.0236 (5)
C5	0.2249 (9)	0.03923 (15)	0.64303 (13)	0.0327 (7)
H5	0.1071	−0.0095	0.6505	0.039*
C6	0.3222 (9)	0.08608 (15)	0.70710 (14)	0.0316 (7)
H6	0.2668	0.0686	0.7566	0.038*
C7	0.4977 (8)	0.15734 (14)	0.69850 (13)	0.0247 (7)
H7	0.5631	0.1891	0.7412	0.030*
C7A	0.5749 (9)	0.18059 (14)	0.62376 (12)	0.0240 (7)
C9	1.0095 (8)	0.35011 (14)	0.69022 (13)	0.0271 (7)
H9	0.9442	0.3238	0.7354	0.032*
C8A	0.9302 (8)	0.31883 (13)	0.61753 (12)	0.0215 (6)
C10	1.1893 (8)	0.42186 (15)	0.69233 (13)	0.0278 (7)
H10	1.2497	0.4450	0.7402	0.033*
C11	1.2834 (9)	0.46097 (15)	0.62460 (12)	0.0306 (7)
H11	1.3996	0.5106	0.6283	0.037*
C12	1.2102 (8)	0.42857 (13)	0.55180 (13)	0.0287 (6)
H12	1.2812	0.4549	0.5071	0.034*
C12A	1.0309 (8)	0.35686 (13)	0.54717 (13)	0.0239 (6)
C12B	0.9084 (8)	0.30683 (14)	0.48208 (13)	0.0237 (7)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N2	0.0386 (15)	0.0370 (14)	0.0269 (9)	0.0020 (13)	0.0016 (13)	0.0000 (8)
N8	0.0312 (13)	0.0197 (9)	0.0201 (8)	0.0012 (8)	−0.0013 (14)	−0.0010 (8)
C1	0.039 (2)	0.0301 (14)	0.0270 (12)	0.0060 (13)	0.0029 (12)	0.0036 (10)
C3	0.032 (2)	0.0327 (14)	0.0275 (12)	0.0050 (14)	−0.0041 (12)	−0.0055 (11)
C4	0.0239 (19)	0.0273 (13)	0.0383 (13)	0.0011 (12)	−0.0005 (13)	−0.0065 (10)
C3A	0.025 (2)	0.0217 (12)	0.0258 (12)	0.0038 (12)	−0.0023 (11)	−0.0032 (9)
C3B	0.0206 (19)	0.0220 (11)	0.0286 (11)	0.0053 (11)	−0.0013 (12)	0.0004 (10)
C3C	0.0222 (14)	0.0265 (12)	0.0220 (9)	0.0049 (10)	−0.0036 (15)	0.0011 (10)
C5	0.029 (2)	0.0223 (13)	0.0474 (14)	−0.0025 (13)	0.0053 (16)	−0.0019 (11)
C6	0.035 (2)	0.0261 (13)	0.0337 (13)	0.0042 (13)	0.0021 (13)	0.0060 (10)
C7	0.024 (2)	0.0233 (12)	0.0272 (11)	0.0064 (12)	0.0018 (12)	0.0023 (9)
C7A	0.024 (2)	0.0206 (12)	0.0269 (12)	0.0041 (12)	−0.0005 (11)	0.0025 (9)
C9	0.031 (2)	0.0244 (13)	0.0255 (11)	0.0029 (13)	0.0032 (13)	−0.0010 (10)
C8A	0.0194 (19)	0.0200 (12)	0.0252 (11)	0.0045 (12)	0.0010 (11)	0.0001 (9)
C10	0.026 (2)	0.0254 (13)	0.0317 (12)	0.0000 (12)	−0.0012 (12)	−0.0058 (10)
C11	0.029 (2)	0.0225 (13)	0.0402 (14)	0.0019 (13)	0.0024 (13)	−0.0013 (10)
C12	0.0279 (19)	0.0258 (12)	0.0327 (12)	0.0046 (12)	0.0040 (14)	0.0052 (10)
C12A	0.024 (2)	0.0216 (11)	0.0264 (12)	0.0065 (11)	0.0023 (11)	0.0031 (9)
C12B	0.0218 (19)	0.0252 (12)	0.0240 (11)	0.0058 (12)	−0.0004 (11)	0.0009 (9)

Geometric parameters (Å, º) top

N2—C1	1.359 (4)	C5—H5	0.9500
N2—C3	1.371 (4)	C6—C7	1.390 (4)
N8—C3C	1.388 (3)	C6—H6	0.9500
N8—C7A	1.417 (4)	C7—C7A	1.412 (4)
N8—C8A	1.421 (4)	C7—H7	0.9500
C1—C12B	1.424 (4)	C9—C10	1.396 (4)
C1—H1	0.9500	C9—C8A	1.408 (4)
C3—C3A	1.431 (4)	C9—H9	0.9500
C3—H3	0.9500	C8A—C12A	1.456 (4)
C4—C3B	1.399 (4)	C10—C11	1.417 (4)
C4—C5	1.413 (4)	C10—H10	0.9500
C4—H4	0.9500	C11—C12	1.412 (4)
C3A—C3C	1.386 (4)	C11—H11	0.9500
C3A—C3B	1.493 (4)	C12—C12A	1.396 (4)
C3B—C7A	1.454 (4)	C12—H12	0.9500
C3C—C12B	1.382 (4)	C12A—C12B	1.488 (4)
C5—C6	1.415 (4)

C1—N2—C3	120.9 (2)	C6—C7—C7A	117.4 (2)
C3C—N8—C7A	107.9 (2)	C6—C7—H7	121.3
C3C—N8—C8A	106.3 (2)	C7A—C7—H7	121.3
C7A—N8—C8A	145.85 (18)	C7—C7A—N8	130.7 (2)
N2—C1—C12B	122.2 (3)	C7—C7A—C3B	123.0 (3)
N2—C1—H1	118.9	N8—C7A—C3B	106.3 (2)
C12B—C1—H1	118.9	C10—C9—C8A	116.4 (2)
N2—C3—C3A	122.4 (3)	C10—C9—H9	121.8
N2—C3—H3	118.8	C8A—C9—H9	121.8
C3A—C3—H3	118.8	C9—C8A—N8	129.6 (2)
C3B—C4—C5	119.5 (2)	C9—C8A—C12A	123.2 (3)
C3B—C4—H4	120.3	N8—C8A—C12A	107.2 (2)
C5—C4—H4	120.3	C9—C10—C11	121.4 (2)
C3C—C3A—C3	111.8 (3)	C9—C10—H10	119.3
C3C—C3A—C3B	102.9 (2)	C11—C10—H10	119.3
C3—C3A—C3B	145.2 (3)	C12—C11—C10	122.1 (3)
C4—C3B—C7A	117.5 (2)	C12—C11—H11	118.9
C4—C3B—C3A	133.8 (2)	C10—C11—H11	118.9
C7A—C3B—C3A	108.6 (2)	C12A—C12—C11	118.3 (2)
C12B—C3C—C3A	130.1 (2)	C12A—C12—H12	120.9
C12B—C3C—N8	115.7 (3)	C11—C12—H12	120.9
C3A—C3C—N8	114.2 (3)	C12—C12A—C8A	118.5 (2)
C4—C5—C6	121.7 (3)	C12—C12A—C12B	133.1 (2)
C4—C5—H5	119.2	C8A—C12A—C12B	108.4 (2)
C6—C5—H5	119.2	C3C—C12B—C1	112.6 (3)
C7—C6—C5	120.9 (3)	C3C—C12B—C12A	102.5 (2)
C7—C6—H6	119.6	C1—C12B—C12A	144.8 (3)
C5—C6—H6	119.6

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C7—H7···N2ⁱ	0.95	2.59	3.540 (6)	175
C9—H9···N2ⁱ	0.95	2.65	3.594 (6)	175

Symmetry code: (i) x, −y+1/2, z+1/2.

(2NICz-HT) top

Crystal data top

C₁₇H₁₀N₂	D_x = 1.379 Mg m⁻³
M_r = 242.27	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pccn	Cell parameters from 1382 reflections
a = 4.1239 (8) Å	θ = 2.4–22.8°
b = 16.404 (3) Å	µ = 0.08 mm⁻¹
c = 17.252 (3) Å	T = 280 K
V = 1167.1 (4) Å³	Rod, colourless
Z = 4	0.30 × 0.10 × 0.06 mm
F(000) = 504

Data collection top

Bruker KAPPA APEX II CCD diffractometer	778 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.061
ω– and φ–scans	θ_max = 27.9°, θ_min = 2.4°
Absorption correction: multi-scan SADABS	h = −5→5
T_min = 0.569, T_max = 0.746	k = −21→21
12863 measured reflections	l = −22→18
1407 independent reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.043	H-atom parameters constrained
wR(F²) = 0.119	w = 1/[σ²(F_o²) + (0.0457P)² + 0.163P] where P = (F_o² + 2F_c²)/3
S = 1.00	(Δ/σ)_max < 0.001
1407 reflections	Δρ_max = 0.17 e Å⁻³
88 parameters	Δρ_min = −0.18 e Å⁻³

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
N2	0.7500	0.2500	0.36577 (11)	0.0695 (7)
N8	0.7500	0.2500	0.59642 (10)	0.0449 (5)
C1	0.5971 (5)	0.18973 (11)	0.40413 (11)	0.0641 (6)
H1	0.4935	0.1492	0.3757	0.077*
C4	0.2912 (5)	0.06864 (10)	0.55981 (11)	0.0582 (5)
H4	0.2234	0.0400	0.5162	0.070*
C3A	0.5884 (4)	0.18587 (9)	0.48492 (9)	0.0493 (5)
C3B	0.4686 (4)	0.13960 (10)	0.55158 (9)	0.0464 (4)
C3C	0.7500	0.2500	0.51798 (13)	0.0473 (6)
C5	0.2154 (5)	0.04062 (11)	0.63275 (11)	0.0635 (6)
H5	0.0973	−0.0073	0.6382	0.076*
C6	0.3132 (4)	0.08307 (10)	0.69824 (11)	0.0580 (5)
H6	0.2561	0.0633	0.7469	0.070*
C7	0.4930 (4)	0.15391 (9)	0.69317 (9)	0.0489 (4)
H2	0.5583	0.1820	0.7373	0.059*
C7A	0.5717 (4)	0.18124 (9)	0.61984 (8)	0.0419 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N2	0.0817 (18)	0.0909 (17)	0.0358 (12)	0.0068 (15)	0.000	0.000
N8	0.0591 (14)	0.0467 (11)	0.0288 (10)	0.0012 (10)	0.000	0.000
C1	0.0702 (14)	0.0785 (14)	0.0436 (12)	0.0096 (12)	−0.0077 (9)	−0.0111 (9)
C4	0.0532 (11)	0.0585 (11)	0.0628 (12)	0.0015 (10)	−0.0018 (10)	−0.0122 (9)
C3A	0.0542 (11)	0.0574 (10)	0.0364 (10)	0.0100 (8)	−0.0052 (8)	−0.0068 (8)
C3B	0.0458 (10)	0.0475 (9)	0.0459 (10)	0.0084 (8)	−0.0028 (8)	−0.0035 (7)
C3C	0.0546 (16)	0.0557 (14)	0.0317 (13)	0.0096 (12)	0.000	0.000
C5	0.0606 (13)	0.0540 (11)	0.0757 (14)	−0.0048 (9)	0.0046 (11)	0.0008 (10)
C6	0.0590 (12)	0.0588 (11)	0.0562 (12)	0.0045 (9)	0.0061 (10)	0.0123 (9)
C7	0.0545 (10)	0.0515 (9)	0.0406 (10)	0.0070 (9)	−0.0004 (8)	0.0048 (8)
C7A	0.0459 (9)	0.0422 (9)	0.0376 (10)	0.0067 (8)	−0.0006 (7)	0.0011 (7)

Geometric parameters (Å, º) top

N2—C1ⁱ	1.346 (2)	C3A—C3C	1.3697 (18)
N2—C1	1.346 (2)	C3A—C3B	1.464 (2)
N8—C3C	1.353 (3)	C3B—C7A	1.426 (2)
N8—C7Aⁱ	1.4056 (17)	C3C—C3Aⁱ	1.3696 (18)
N8—C7A	1.4057 (17)	C5—C6	1.387 (2)
C1—C3A	1.396 (2)	C5—H5	0.9300
C1—H1	0.9300	C6—C7	1.381 (2)
C4—C5	1.376 (2)	C6—H6	0.9300
C4—C3B	1.382 (2)	C7—C7A	1.381 (2)
C4—H4	0.9300	C7—H2	0.9300

C1ⁱ—N2—C1	121.1 (2)	N8—C3C—C3Aⁱ	114.61 (11)
C3C—N8—C7Aⁱ	106.70 (9)	N8—C3C—C3A	114.61 (11)
C3C—N8—C7A	106.70 (9)	C3Aⁱ—C3C—C3A	130.8 (2)
C7Aⁱ—N8—C7A	146.59 (18)	C4—C5—C6	120.75 (19)
N2—C1—C3A	122.42 (19)	C4—C5—H5	119.6
N2—C1—H1	118.8	C6—C5—H5	119.6
C3A—C1—H1	118.8	C7—C6—C5	121.79 (17)
C5—C4—C3B	119.71 (17)	C7—C6—H6	119.1
C5—C4—H4	120.1	C5—C6—H6	119.1
C3B—C4—H4	120.1	C7A—C7—C6	117.21 (16)
C3C—C3A—C1	111.62 (17)	C7A—C7—H2	121.4
C3C—C3A—C3B	103.61 (14)	C6—C7—H2	121.4
C1—C3A—C3B	144.76 (17)	C7—C7A—N8	130.30 (15)
C4—C3B—C7A	118.45 (15)	C7—C7A—C3B	122.06 (16)
C4—C3B—C3A	134.11 (16)	N8—C7A—C3B	107.64 (14)
C7A—C3B—C3A	107.43 (14)

Symmetry code: (i) −x+3/2, −y+1/2, z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C7—H2···N2ⁱⁱ	0.93	2.60	3.532 (2)	176

Symmetry code: (ii) x, −y+1/2, z+1/2.

(5NICz-LT) top

Crystal data top

C₁₇H₁₀N₂	D_x = 1.368 Mg m⁻³
M_r = 242.27	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pca2₁	Cell parameters from 2682 reflections
a = 7.394 (9) Å	θ = 2.3–24.2°
b = 10.953 (13) Å	µ = 0.08 mm⁻¹
c = 29.06 (3) Å	T = 150 K
V = 2353 (5) Å³	Rod, colourless
Z = 8	0.55 × 0.16 × 0.10 mm
F(000) = 1008

Data collection top

Bruker KAPPA APEX II CCD diffractometer	2598 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.075
ω– and φ–scans	θ_max = 25.1°, θ_min = 1.9°
Absorption correction: multi-scan SADABS	h = −8→8
T_min = 0.552, T_max = 0.745	k = −12→12
11809 measured reflections	l = −34→34
3757 independent reflections

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.098	w = 1/[σ²(F_o²) + (0.1934P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.276	(Δ/σ)_max = 0.002
S = 1.03	Δρ_max = 0.65 e Å⁻³
3757 reflections	Δρ_min = −0.33 e Å⁻³
343 parameters	Absolute structure: Flack x determined using 904 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons, Flack and Wagner, Acta Cryst. B69 (2013) 249-259).
1 restraint	Absolute structure parameter: −4.5 (10)

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
N8	0.3920 (11)	0.8910 (7)	0.6055 (3)	0.029 (2)
N5	0.5583 (11)	1.1316 (8)	0.5031 (3)	0.037 (2)
C7a	0.4543 (12)	0.9550 (9)	0.5675 (3)	0.023 (2)
C7	0.5231 (12)	0.9159 (9)	0.5243 (3)	0.029 (2)
H7	0.5370	0.8320	0.5168	0.034*
C6	0.5683 (13)	1.0077 (8)	0.4938 (3)	0.027 (3)
H6	0.6095	0.9841	0.4641	0.033*
C4	0.4907 (14)	1.1647 (9)	0.5434 (3)	0.035 (2)
H4	0.4763	1.2491	0.5499	0.042*
C3b	0.4399 (13)	1.0792 (9)	0.5764 (3)	0.027 (2)
C3c	0.3420 (15)	0.9708 (11)	0.6369 (3)	0.034 (3)
C3a	0.3627 (12)	1.0936 (9)	0.6249 (3)	0.026 (2)
C3	0.3055 (13)	1.1769 (10)	0.6589 (3)	0.033 (3)
H3	0.3149	1.2625	0.6541	0.040*
C2	0.2337 (16)	1.1291 (11)	0.7002 (4)	0.044 (3)
H2	0.1935	1.1863	0.7226	0.053*
C1	0.2163 (15)	1.0040 (10)	0.7113 (4)	0.039 (3)
H1	0.1677	0.9779	0.7399	0.047*
C12b	0.2743 (13)	0.9208 (9)	0.6780 (3)	0.032 (2)
C8a	0.3569 (12)	0.7721 (9)	0.6222 (3)	0.029 (2)
C12a	0.2833 (12)	0.7880 (9)	0.6673 (3)	0.029 (2)
C12	0.2280 (14)	0.6843 (10)	0.6916 (4)	0.041 (3)
H12	0.1761	0.6924	0.7214	0.049*
C11	0.2493 (15)	0.5685 (10)	0.6720 (4)	0.041 (3)
H11	0.2153	0.4976	0.6887	0.049*
C10	0.3220 (14)	0.5576 (9)	0.6269 (4)	0.038 (3)
H10	0.3330	0.4788	0.6135	0.045*
C9	0.3778 (14)	0.6593 (9)	0.6017 (4)	0.035 (2)
H9	0.4280	0.6513	0.5717	0.042*
N8'	0.8286 (10)	0.3857 (7)	0.3955 (3)	0.0269 (18)
N5'	0.6703 (10)	0.6313 (7)	0.4980 (3)	0.032 (2)
C7a'	0.7681 (12)	0.4549 (9)	0.4334 (3)	0.027 (2)
C7'	0.7036 (13)	0.4203 (8)	0.4769 (4)	0.032 (2)
H7'	0.6939	0.3368	0.4853	0.038*
C6'	0.6555 (13)	0.5105 (9)	0.5065 (4)	0.029 (3)
H6'	0.6077	0.4868	0.5355	0.035*
C4'	0.7339 (14)	0.6641 (9)	0.4563 (4)	0.034 (2)
H4'	0.7451	0.7488	0.4499	0.041*
C3b'	0.7841 (12)	0.5824 (8)	0.4224 (4)	0.027 (2)
C3c'	0.8836 (13)	0.4705 (10)	0.3613 (3)	0.027 (2)
C3a'	0.8604 (12)	0.5897 (9)	0.3758 (4)	0.028 (2)
C3'	0.9174 (13)	0.6726 (10)	0.3405 (4)	0.037 (3)
H3'	0.9095	0.7583	0.3453	0.044*
C2'	0.9840 (13)	0.6269 (10)	0.2995 (4)	0.038 (3)
H2'	1.0179	0.6838	0.2763	0.045*
C1'	1.0053 (15)	0.5003 (9)	0.2895 (3)	0.028 (2)
H1'	1.0547	0.4750	0.2609	0.034*
C12b'	0.9531 (13)	0.4141 (9)	0.3222 (3)	0.031 (2)
C8a'	0.8686 (12)	0.2703 (8)	0.3780 (3)	0.028 (2)
C12a'	0.9474 (13)	0.2849 (10)	0.3335 (4)	0.035 (3)
C12'	0.9999 (14)	0.1798 (9)	0.3097 (4)	0.036 (2)
H12'	1.0492	0.1849	0.2795	0.043*
C11'	0.9779 (16)	0.0673 (9)	0.3314 (3)	0.039 (3)
H11'	1.0174	−0.0041	0.3158	0.047*
C10'	0.9016 (15)	0.0548 (10)	0.3744 (4)	0.042 (3)
H10'	0.8866	−0.0244	0.3871	0.051*
C9'	0.8466 (14)	0.1556 (8)	0.3992 (3)	0.029 (2)
H9'	0.7964	0.1479	0.4291	0.035*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N8	0.028 (5)	0.027 (5)	0.033 (5)	−0.001 (4)	−0.006 (4)	0.004 (4)
N5	0.037 (5)	0.028 (5)	0.044 (5)	0.004 (4)	0.004 (4)	−0.002 (4)
C7a	0.017 (5)	0.029 (6)	0.021 (5)	0.011 (4)	0.001 (4)	−0.003 (5)
C7	0.018 (5)	0.030 (6)	0.038 (5)	−0.003 (4)	−0.002 (4)	0.001 (4)
C6	0.042 (6)	0.030 (7)	0.009 (4)	0.001 (4)	−0.006 (4)	0.001 (3)
C4	0.038 (6)	0.027 (6)	0.040 (6)	−0.001 (5)	−0.006 (5)	0.000 (5)
C3b	0.026 (6)	0.029 (6)	0.025 (5)	0.003 (4)	−0.006 (4)	−0.007 (4)
C3c	0.045 (7)	0.041 (6)	0.015 (5)	0.008 (5)	−0.009 (4)	−0.007 (4)
C3a	0.012 (5)	0.028 (6)	0.038 (5)	0.004 (4)	−0.009 (4)	−0.001 (5)
C3	0.034 (6)	0.035 (6)	0.031 (6)	0.013 (5)	−0.003 (5)	0.011 (5)
C2	0.036 (6)	0.050 (8)	0.045 (7)	0.000 (5)	−0.008 (5)	−0.009 (5)
C1	0.029 (7)	0.051 (8)	0.037 (6)	0.006 (5)	0.008 (5)	0.002 (5)
C12b	0.019 (5)	0.044 (6)	0.034 (5)	−0.003 (4)	−0.003 (4)	0.010 (5)
C8a	0.029 (6)	0.036 (6)	0.022 (4)	−0.006 (4)	−0.006 (4)	−0.004 (4)
C12a	0.025 (5)	0.036 (6)	0.026 (5)	−0.007 (4)	−0.010 (4)	−0.001 (4)
C12	0.037 (6)	0.051 (8)	0.035 (6)	−0.008 (5)	−0.001 (5)	0.004 (5)
C11	0.032 (6)	0.044 (7)	0.046 (6)	−0.008 (5)	0.004 (5)	0.013 (5)
C10	0.040 (6)	0.022 (6)	0.051 (6)	−0.004 (4)	−0.006 (6)	−0.005 (5)
C9	0.028 (5)	0.041 (7)	0.036 (5)	−0.006 (5)	−0.001 (4)	−0.006 (5)
N8'	0.011 (4)	0.021 (4)	0.049 (5)	0.000 (3)	−0.001 (3)	0.001 (4)
N5'	0.025 (5)	0.030 (5)	0.041 (5)	0.004 (4)	0.003 (4)	−0.006 (4)
C7a'	0.015 (5)	0.034 (6)	0.031 (5)	0.016 (4)	−0.003 (4)	−0.010 (5)
C7'	0.034 (6)	0.014 (5)	0.046 (6)	−0.007 (4)	0.000 (5)	0.005 (4)
C6'	0.020 (5)	0.025 (7)	0.042 (6)	0.002 (4)	−0.001 (4)	−0.003 (4)
C4'	0.028 (5)	0.019 (6)	0.056 (6)	−0.006 (4)	−0.001 (5)	−0.008 (5)
C3b'	0.013 (5)	0.016 (5)	0.052 (6)	0.002 (4)	−0.008 (5)	−0.010 (5)
C3c'	0.015 (5)	0.036 (6)	0.030 (5)	0.014 (4)	−0.003 (4)	−0.007 (5)
C3a'	0.009 (4)	0.028 (6)	0.048 (6)	−0.003 (4)	−0.010 (4)	0.011 (5)
C3'	0.014 (5)	0.036 (7)	0.061 (7)	0.002 (4)	−0.009 (5)	0.012 (5)
C2'	0.021 (5)	0.038 (7)	0.054 (7)	−0.002 (4)	0.007 (5)	0.023 (5)
C1'	0.031 (5)	0.040 (7)	0.013 (5)	−0.003 (4)	−0.003 (4)	0.006 (4)
C12b'	0.018 (6)	0.038 (6)	0.037 (5)	0.001 (4)	−0.012 (4)	0.004 (4)
C8a'	0.024 (5)	0.020 (5)	0.039 (6)	−0.001 (4)	−0.009 (4)	−0.006 (4)
C12a'	0.022 (5)	0.035 (7)	0.049 (7)	0.004 (4)	0.002 (5)	0.000 (5)
C12'	0.026 (5)	0.037 (6)	0.044 (6)	−0.001 (5)	−0.006 (5)	−0.004 (5)
C11'	0.045 (7)	0.030 (6)	0.044 (6)	0.012 (5)	−0.005 (5)	−0.014 (5)
C10'	0.049 (7)	0.035 (7)	0.043 (6)	−0.007 (5)	−0.006 (5)	−0.008 (5)
C9'	0.032 (5)	0.013 (5)	0.042 (5)	0.000 (4)	−0.002 (4)	−0.003 (4)

Geometric parameters (Å, º) top

N8—C3c	1.316 (13)	N8'—C8a'	1.395 (12)
N8—C7a	1.386 (12)	N8'—C7a'	1.409 (12)
N8—C8a	1.413 (12)	N8'—C3c'	1.420 (14)
N5—C4	1.322 (13)	N5'—C4'	1.347 (13)
N5—C6	1.386 (12)	N5'—C6'	1.350 (12)
C7a—C3b	1.389 (13)	C7a'—C7'	1.403 (14)
C7a—C7	1.423 (13)	C7a'—C3b'	1.438 (14)
C7—C6	1.381 (13)	C7'—C6'	1.358 (13)
C7—H7	0.9500	C7'—H7'	0.9500
C6—H6	0.9500	C6'—H6'	0.9500
C4—C3b	1.394 (14)	C4'—C3b'	1.384 (13)
C4—H4	0.9500	C4'—H4'	0.9500
C3b—C3a	1.526 (13)	C3b'—C3a'	1.467 (14)
C3c—C3a	1.398 (14)	C3c'—C3a'	1.382 (14)
C3c—C12b	1.406 (14)	C3c'—C12b'	1.394 (14)
C3a—C3	1.410 (14)	C3a'—C3'	1.434 (14)
C3—C2	1.415 (15)	C3'—C2'	1.385 (15)
C3—H3	0.9500	C3'—H3'	0.9500
C2—C1	1.413 (15)	C2'—C1'	1.424 (15)
C2—H2	0.9500	C2'—H2'	0.9500
C1—C12b	1.397 (15)	C1'—C12b'	1.394 (13)
C1—H1	0.9500	C1'—H1'	0.9500
C12b—C12a	1.489 (14)	C12b'—C12a'	1.453 (15)
C8a—C9	1.379 (13)	C8a'—C9'	1.408 (13)
C8a—C12a	1.430 (13)	C8a'—C12a'	1.428 (14)
C12a—C12	1.399 (14)	C12a'—C12'	1.399 (14)
C12—C11	1.399 (15)	C12'—C11'	1.394 (14)
C12—H12	0.9500	C12'—H12'	0.9500
C11—C10	1.421 (14)	C11'—C10'	1.376 (15)
C11—H11	0.9500	C11'—H11'	0.9500
C10—C9	1.395 (14)	C10'—C9'	1.380 (14)
C10—H10	0.9500	C10'—H10'	0.9500
C9—H9	0.9500	C9'—H9'	0.9500

C3c—N8—C7a	108.0 (8)	C8a'—N8'—C7a'	147.1 (9)
C3c—N8—C8a	108.9 (9)	C8a'—N8'—C3c'	106.1 (8)
C7a—N8—C8a	143.1 (9)	C7a'—N8'—C3c'	106.6 (8)
C4—N5—C6	117.5 (9)	C4'—N5'—C6'	117.1 (9)
N8—C7a—C3b	108.8 (8)	C7'—C7a'—N8'	131.8 (9)
N8—C7a—C7	132.1 (9)	C7'—C7a'—C3b'	119.5 (9)
C3b—C7a—C7	119.1 (9)	N8'—C7a'—C3b'	108.8 (8)
C6—C7—C7a	115.8 (9)	C6'—C7'—C7a'	117.6 (9)
C6—C7—H7	122.1	C6'—C7'—H7'	121.2
C7a—C7—H7	122.1	C7a'—C7'—H7'	121.2
C7—C6—N5	125.0 (9)	N5'—C6'—C7'	125.0 (10)
C7—C6—H6	117.5	N5'—C6'—H6'	117.5
N5—C6—H6	117.5	C7'—C6'—H6'	117.5
N5—C4—C3b	121.8 (10)	N5'—C4'—C3b'	124.2 (10)
N5—C4—H4	119.1	N5'—C4'—H4'	117.9
C3b—C4—H4	119.1	C3b'—C4'—H4'	117.9
C7a—C3b—C4	120.6 (9)	C4'—C3b'—C7a'	116.5 (10)
C7a—C3b—C3a	107.5 (8)	C4'—C3b'—C3a'	136.5 (10)
C4—C3b—C3a	131.9 (9)	C7a'—C3b'—C3a'	106.9 (8)
N8—C3c—C3a	115.8 (9)	C3a'—C3c'—C12b'	135.5 (11)
N8—C3c—C12b	115.5 (10)	C3a'—C3c'—N8'	111.7 (8)
C3a—C3c—C12b	128.7 (10)	C12b'—C3c'—N8'	112.8 (9)
C3c—C3a—C3	114.5 (10)	C3c'—C3a'—C3'	110.1 (10)
C3c—C3a—C3b	99.9 (8)	C3c'—C3a'—C3b'	106.1 (9)
C3—C3a—C3b	145.6 (10)	C3'—C3a'—C3b'	143.8 (11)
C3a—C3—C2	118.0 (10)	C2'—C3'—C3a'	119.5 (10)
C3a—C3—H3	121.0	C2'—C3'—H3'	120.3
C2—C3—H3	121.0	C3a'—C3'—H3'	120.3
C1—C2—C3	125.9 (11)	C3'—C2'—C1'	124.5 (9)
C1—C2—H2	117.0	C3'—C2'—H2'	117.7
C3—C2—H2	117.0	C1'—C2'—H2'	117.7
C12b—C1—C2	116.5 (11)	C12b'—C1'—C2'	119.3 (10)
C12b—C1—H1	121.7	C12b'—C1'—H1'	120.3
C2—C1—H1	121.7	C2'—C1'—H1'	120.3
C1—C12b—C3c	116.4 (10)	C3c'—C12b'—C1'	111.0 (10)
C1—C12b—C12a	142.7 (10)	C3c'—C12b'—C12a'	103.7 (9)
C3c—C12b—C12a	100.8 (9)	C1'—C12b'—C12a'	145.3 (10)
C9—C8a—N8	131.1 (9)	N8'—C8a'—C9'	128.7 (9)
C9—C8a—C12a	123.2 (9)	N8'—C8a'—C12a'	108.4 (8)
N8—C8a—C12a	105.7 (8)	C9'—C8a'—C12a'	122.9 (9)
C12—C12a—C8a	118.4 (9)	C12'—C12a'—C8a'	118.0 (9)
C12—C12a—C12b	132.4 (9)	C12'—C12a'—C12b'	132.9 (10)
C8a—C12a—C12b	109.1 (8)	C8a'—C12a'—C12b'	109.1 (9)
C11—C12—C12a	119.8 (10)	C11'—C12'—C12a'	118.1 (10)
C11—C12—H12	120.1	C11'—C12'—H12'	121.0
C12a—C12—H12	120.1	C12a'—C12'—H12'	121.0
C12—C11—C10	119.6 (9)	C10'—C11'—C12'	123.2 (10)
C12—C11—H11	120.2	C10'—C11'—H11'	118.4
C10—C11—H11	120.2	C12'—C11'—H11'	118.4
C9—C10—C11	121.9 (9)	C11'—C10'—C9'	121.0 (10)
C9—C10—H10	119.0	C11'—C10'—H10'	119.5
C11—C10—H10	119.0	C9'—C10'—H10'	119.5
C8a—C9—C10	117.1 (10)	C10'—C9'—C8a'	116.8 (9)
C8a—C9—H9	121.5	C10'—C9'—H9'	121.6
C10—C9—H9	121.5	C8a'—C9'—H9'	121.6

(5NICz-HT) top

Crystal data top

C₁₇H₁₀N₂	F(000) = 1008
M_r = 242.27	D_x = 1.351 Mg m⁻³
Monoclinic, P2₁/a	Mo Kα radiation, λ = 0.71073 Å
a = 8.2204 (15) Å	Cell parameters from 5589 reflections
b = 10.898 (2) Å	θ = 2.4–24.5°
c = 26.905 (5) Å	µ = 0.08 mm⁻¹
β = 98.691 (4)°	T = 270 K
V = 2382.6 (8) Å³	Rod, colourless
Z = 8	0.55 × 0.16 × 0.10 mm

Data collection top

Bruker KAPPA APEX II CCD diffractometer	3042 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.077
ω– and φ–scans	θ_max = 27.9°, θ_min = 0.8°
Absorption correction: multi-scan SADABS	h = −10→10
T_min = 0.600, T_max = 0.746	k = −14→14
36052 measured reflections	l = −35→35
5710 independent reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.091	H-atom parameters constrained
wR(F²) = 0.280	w = 1/[σ²(F_o²) + (0.1526P)² + 0.4185P] where P = (F_o² + 2F_c²)/3
S = 1.06	(Δ/σ)_max < 0.001
5710 reflections	Δρ_max = 0.50 e Å⁻³
344 parameters	Δρ_min = −0.30 e Å⁻³

Special details top

Refinement. Refined as a 2-component twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
N8'	0.4536 (5)	0.8442 (3)	0.39521 (12)	0.0383 (8)
N5'	0.2873 (5)	0.6027 (3)	0.49502 (15)	0.0502 (10)
C7a'	0.3905 (5)	0.7776 (4)	0.43265 (14)	0.0341 (9)
C7'	0.3232 (6)	0.8153 (4)	0.47345 (15)	0.0406 (10)
H7'	0.3127	0.8981	0.4808	0.049*
C6'	0.2714 (7)	0.7248 (4)	0.50331 (15)	0.0466 (12)
H6'	0.2226	0.7487	0.5308	0.056*
C4'	0.3517 (6)	0.5677 (4)	0.45473 (16)	0.0453 (11)
H4'	0.3590	0.4842	0.4483	0.054*
C3b'	0.4090 (5)	0.6513 (4)	0.42151 (17)	0.0402 (10)
C3c'	0.5066 (6)	0.7591 (4)	0.36274 (14)	0.0371 (10)
C3a'	0.4833 (6)	0.6411 (4)	0.37711 (18)	0.0418 (11)
C3'	0.5438 (6)	0.5571 (4)	0.34273 (18)	0.0501 (12)
H3'	0.5363	0.4728	0.3472	0.060*
C2'	0.6132 (7)	0.6037 (5)	0.3030 (2)	0.0641 (15)
H2'	0.6526	0.5477	0.2816	0.077*
C1'	0.6290 (8)	0.7296 (5)	0.29225 (16)	0.0542 (13)
H1'	0.6734	0.7549	0.2641	0.065*
C12b'	0.5771 (6)	0.8133 (4)	0.32436 (15)	0.0458 (11)
C8a'	0.4897 (5)	0.9607 (3)	0.37885 (15)	0.0374 (10)
C12a'	0.5657 (6)	0.9463 (4)	0.33563 (16)	0.0424 (10)
C12'	0.6182 (7)	1.0510 (5)	0.31181 (17)	0.0553 (13)
H12'	0.6664	1.0438	0.2828	0.066*
C11'	0.5962 (8)	1.1659 (4)	0.33271 (19)	0.0649 (15)
H11'	0.6333	1.2360	0.3182	0.078*
C10'	0.5194 (7)	1.1761 (4)	0.37491 (18)	0.0574 (14)
H10'	0.5041	1.2538	0.3877	0.069*
C9'	0.4648 (7)	1.0755 (4)	0.39864 (16)	0.0478 (11)
H9'	0.4130	1.0842	0.4269	0.057*
N8	0.0465 (7)	0.3456 (5)	0.10618 (16)	0.0692 (14)
N5	−0.2068 (9)	0.1025 (5)	0.0078 (2)	0.0859 (17)
C7a	−0.0470 (8)	0.2764 (6)	0.06971 (17)	0.0590 (15)
C7	−0.1530 (8)	0.3130 (6)	0.02798 (19)	0.0702 (17)
H7	−0.1730	0.3952	0.0201	0.084*
C6	−0.2264 (10)	0.2212 (6)	−0.00093 (19)	0.0742 (18)
H6	−0.2975	0.2438	−0.0297	0.089*
C4	−0.1037 (9)	0.0688 (6)	0.0479 (2)	0.0770 (19)
H4	−0.0866	−0.0146	0.0540	0.092*
C3b	−0.0211 (8)	0.1507 (6)	0.0810 (2)	0.0606 (15)
C3c	0.1315 (8)	0.2639 (6)	0.13853 (18)	0.0614 (15)
C3a	0.0973 (8)	0.1416 (6)	0.1266 (2)	0.0658 (16)
C3	0.1884 (10)	0.0627 (7)	0.1612 (3)	0.083 (2)
H3	0.1759	−0.0218	0.1573	0.100*
C2	0.2948 (10)	0.1083 (7)	0.2002 (3)	0.093 (2)
H2	0.3497	0.0521	0.2228	0.112*
C1	0.3303 (12)	0.2374 (8)	0.2098 (2)	0.092 (2)
H1	0.4098	0.2640	0.2359	0.110*
C12b	0.2355 (8)	0.3198 (6)	0.17671 (19)	0.0692 (17)
C8a	0.1030 (8)	0.4643 (5)	0.12221 (19)	0.0624 (15)
C12a	0.2205 (8)	0.4513 (6)	0.1657 (2)	0.0684 (17)
C12	0.2943 (9)	0.5567 (6)	0.1870 (2)	0.082 (2)
H12	0.3723	0.5518	0.2158	0.098*
C11	0.2510 (10)	0.6713 (7)	0.1648 (2)	0.093 (2)
H11	0.3022	0.7423	0.1785	0.111*
C10	0.1333 (11)	0.6784 (6)	0.1228 (2)	0.088 (2)
H10	0.1048	0.7552	0.1091	0.105*
C9	0.0567 (9)	0.5776 (6)	0.1006 (2)	0.0766 (19)
H9	−0.0229	0.5840	0.0722	0.092*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N8'	0.038 (2)	0.0255 (16)	0.051 (2)	0.0036 (15)	0.0045 (17)	−0.0040 (15)
N5'	0.055 (3)	0.0290 (18)	0.066 (2)	−0.0041 (17)	0.010 (2)	0.0066 (17)
C7a'	0.026 (2)	0.035 (2)	0.041 (2)	−0.0029 (18)	0.0058 (19)	0.0016 (18)
C7'	0.045 (3)	0.027 (2)	0.051 (2)	−0.0006 (18)	0.011 (2)	0.0013 (17)
C6'	0.051 (3)	0.040 (3)	0.050 (2)	−0.007 (2)	0.010 (2)	0.005 (2)
C4'	0.045 (3)	0.024 (2)	0.064 (3)	−0.0006 (18)	0.000 (2)	0.0028 (19)
C3b'	0.029 (2)	0.032 (2)	0.056 (2)	0.0009 (17)	−0.007 (2)	−0.0020 (18)
C3c'	0.030 (3)	0.044 (2)	0.037 (2)	−0.0004 (17)	0.004 (2)	−0.0053 (17)
C3a'	0.032 (2)	0.027 (2)	0.061 (3)	−0.0010 (17)	−0.009 (2)	−0.0048 (18)
C3'	0.042 (3)	0.038 (2)	0.068 (3)	0.003 (2)	0.002 (3)	−0.013 (2)
C2'	0.054 (3)	0.069 (4)	0.069 (3)	−0.003 (3)	0.010 (3)	−0.026 (3)
C1'	0.039 (3)	0.079 (4)	0.046 (2)	−0.011 (3)	0.010 (3)	−0.009 (3)
C12b'	0.034 (3)	0.058 (3)	0.043 (2)	0.001 (2)	−0.001 (2)	−0.004 (2)
C8a'	0.042 (2)	0.0232 (19)	0.044 (2)	−0.0035 (16)	−0.004 (2)	0.0052 (16)
C12a'	0.036 (2)	0.048 (2)	0.040 (2)	−0.0073 (19)	−0.002 (2)	0.004 (2)
C12'	0.053 (3)	0.066 (3)	0.046 (2)	−0.003 (3)	0.001 (2)	0.013 (2)
C11'	0.072 (4)	0.046 (3)	0.075 (3)	−0.010 (3)	0.006 (3)	0.022 (3)
C10'	0.066 (3)	0.033 (2)	0.071 (3)	−0.004 (2)	0.000 (3)	0.011 (2)
C9'	0.058 (3)	0.028 (2)	0.055 (3)	−0.001 (2)	0.001 (2)	−0.0014 (19)
N8	0.082 (4)	0.067 (3)	0.061 (3)	−0.003 (3)	0.017 (3)	−0.003 (2)
N5	0.104 (5)	0.077 (4)	0.077 (3)	−0.007 (3)	0.018 (3)	−0.008 (3)
C7a	0.064 (4)	0.073 (4)	0.041 (2)	−0.001 (3)	0.014 (3)	0.004 (3)
C7	0.074 (4)	0.077 (4)	0.061 (3)	−0.003 (3)	0.013 (3)	0.004 (3)
C6	0.079 (5)	0.080 (5)	0.062 (3)	0.001 (4)	0.007 (4)	−0.007 (3)
C4	0.091 (5)	0.066 (4)	0.077 (4)	0.008 (3)	0.022 (4)	−0.003 (3)
C3b	0.057 (4)	0.067 (4)	0.060 (3)	−0.001 (3)	0.018 (3)	0.008 (3)
C3c	0.060 (4)	0.071 (4)	0.054 (3)	0.003 (3)	0.011 (3)	0.008 (3)
C3a	0.059 (4)	0.076 (4)	0.065 (3)	−0.002 (3)	0.022 (3)	0.009 (3)
C3	0.085 (5)	0.087 (5)	0.082 (4)	0.012 (4)	0.027 (4)	0.032 (4)
C2	0.076 (5)	0.111 (6)	0.093 (5)	0.010 (4)	0.017 (4)	0.051 (4)
C1	0.088 (6)	0.120 (6)	0.065 (4)	0.019 (5)	0.006 (4)	0.025 (4)
C12b	0.066 (4)	0.088 (5)	0.054 (3)	−0.001 (3)	0.012 (3)	0.004 (3)
C8a	0.066 (4)	0.069 (4)	0.051 (3)	−0.003 (3)	0.010 (3)	−0.004 (3)
C12a	0.072 (4)	0.083 (4)	0.055 (3)	−0.011 (3)	0.024 (3)	−0.014 (3)
C12	0.086 (5)	0.102 (5)	0.057 (3)	−0.017 (4)	0.010 (3)	−0.018 (3)
C11	0.104 (6)	0.092 (5)	0.084 (4)	−0.013 (4)	0.018 (4)	−0.022 (4)
C10	0.116 (7)	0.077 (5)	0.072 (4)	0.003 (4)	0.019 (4)	−0.003 (3)
C9	0.097 (5)	0.073 (4)	0.060 (3)	−0.003 (4)	0.013 (4)	−0.004 (3)

Geometric parameters (Å, º) top

N8'—C3c'	1.389 (5)	N8—C3c	1.362 (7)
N8'—C8a'	1.390 (5)	N8—C7a	1.376 (7)
N8'—C7a'	1.403 (5)	N8—C8a	1.419 (7)
N5'—C4'	1.332 (6)	N5—C6	1.320 (8)
N5'—C6'	1.358 (6)	N5—C4	1.320 (8)
C7a'—C7'	1.365 (6)	C7a—C7	1.372 (7)
C7a'—C3b'	1.422 (6)	C7a—C3b	1.413 (8)
C7'—C6'	1.380 (6)	C7—C6	1.352 (8)
C4'—C3b'	1.407 (6)	C4—C3b	1.366 (8)
C3b'—C3a'	1.425 (7)	C3b—C3a	1.450 (8)
C3c'—C3a'	1.365 (6)	C3c—C12b	1.375 (7)
C3c'—C12b'	1.389 (6)	C3c—C3a	1.389 (8)
C3a'—C3'	1.443 (6)	C3a—C3	1.398 (9)
C3'—C2'	1.383 (7)	C3—C2	1.357 (10)
C2'—C1'	1.412 (8)	C2—C1	1.452 (11)
C1'—C12b'	1.368 (6)	C1—C12b	1.413 (9)
C12b'—C12a'	1.487 (6)	C12b—C12a	1.465 (8)
C8a'—C9'	1.388 (6)	C8a—C9	1.393 (8)
C8a'—C12a'	1.409 (6)	C8a—C12a	1.408 (8)
C12a'—C12'	1.408 (6)	C12a—C12	1.381 (8)
C12'—C11'	1.395 (7)	C12—C11	1.407 (9)
C11'—C10'	1.384 (7)	C11—C10	1.373 (9)
C10'—C9'	1.378 (6)	C10—C9	1.360 (9)

C3c'—N8'—C8a'	108.0 (3)	C3c—N8—C7a	106.0 (5)
C3c'—N8'—C7a'	106.9 (3)	C3c—N8—C8a	106.8 (5)
C8a'—N8'—C7a'	145.0 (4)	C7a—N8—C8a	146.9 (5)
C4'—N5'—C6'	118.3 (4)	C6—N5—C4	117.7 (6)
C7'—C7a'—N8'	131.3 (4)	C7—C7a—N8	129.9 (6)
C7'—C7a'—C3b'	122.0 (4)	C7—C7a—C3b	120.9 (6)
N8'—C7a'—C3b'	106.6 (4)	N8—C7a—C3b	109.1 (5)
C7a'—C7'—C6'	116.8 (4)	C6—C7—C7a	115.4 (6)
N5'—C6'—C7'	124.0 (4)	N5—C6—C7	126.2 (6)
N5'—C4'—C3b'	123.0 (4)	N5—C4—C3b	123.0 (6)
C4'—C3b'—C7a'	115.9 (4)	C4—C3b—C7a	116.7 (6)
C4'—C3b'—C3a'	135.2 (4)	C4—C3b—C3a	135.3 (6)
C7a'—C3b'—C3a'	109.0 (4)	C7a—C3b—C3a	108.0 (5)
C3a'—C3c'—N8'	112.3 (4)	N8—C3c—C12b	112.9 (6)
C3a'—C3c'—C12b'	134.7 (4)	N8—C3c—C3a	114.4 (5)
N8'—C3c'—C12b'	112.9 (4)	C12b—C3c—C3a	132.7 (6)
C3c'—C3a'—C3b'	105.1 (4)	C3c—C3a—C3	111.6 (6)
C3c'—C3a'—C3'	109.9 (4)	C3c—C3a—C3b	102.5 (5)
C3b'—C3a'—C3'	145.1 (4)	C3—C3a—C3b	145.9 (7)
C2'—C3'—C3a'	119.0 (5)	C2—C3—C3a	120.5 (7)
C3'—C2'—C1'	125.2 (5)	C3—C2—C1	125.5 (6)
C12b'—C1'—C2'	118.1 (5)	C12b—C1—C2	115.3 (7)
C1'—C12b'—C3c'	113.0 (4)	C3c—C12b—C1	114.3 (6)
C1'—C12b'—C12a'	144.5 (5)	C3c—C12b—C12a	105.0 (5)
C3c'—C12b'—C12a'	102.5 (4)	C1—C12b—C12a	140.4 (6)
C9'—C8a'—N8'	130.6 (4)	C9—C8a—C12a	123.1 (6)
C9'—C8a'—C12a'	121.8 (4)	C9—C8a—N8	128.7 (5)
N8'—C8a'—C12a'	107.6 (3)	C12a—C8a—N8	108.3 (5)
C12'—C12a'—C8a'	119.4 (4)	C12—C12a—C8a	117.6 (6)
C12'—C12a'—C12b'	131.6 (5)	C12—C12a—C12b	135.4 (6)
C8a'—C12a'—C12b'	109.0 (4)	C8a—C12a—C12b	107.0 (5)
C11'—C12'—C12a'	118.5 (5)	C12a—C12—C11	119.7 (6)
C10'—C11'—C12'	120.4 (4)	C10—C11—C12	120.0 (6)
C9'—C10'—C11'	122.5 (4)	C9—C10—C11	122.6 (6)
C10'—C9'—C8a'	117.5 (5)	C10—C9—C8a	117.0 (6)

(25NICz-1) top

Crystal data top

C₁₆H₉N₃	D_x = 1.455 Mg m⁻³
M_r = 243.26	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pmn2₁	Cell parameters from 2468 reflections
a = 19.316 (4) Å	θ = 2.8–30.2°
b = 3.7013 (8) Å	µ = 0.09 mm⁻¹
c = 7.7676 (18) Å	T = 100 K
V = 555.3 (2) Å³	Plate, colourless
Z = 2	0.45 × 0.23 × 0.03 mm
F(000) = 252

Data collection top

Bruker KAPPA APEX II CCD diffractometer	1458 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.034
ω– and φ–scans	θ_max = 30.3°, θ_min = 2.8°
Absorption correction: multi-scan SADABS	h = −27→22
T_min = 0.424, T_max = 0.493	k = −5→5
5744 measured reflections	l = −10→10
1608 independent reflections

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.041	w = 1/[σ²(F_o²) + (0.0589P)² + 0.0808P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.104	(Δ/σ)_max < 0.001
S = 1.07	Δρ_max = 0.33 e Å⁻³
1608 reflections	Δρ_min = −0.27 e Å⁻³
91 parameters	Absolute structure: Flack x determined using 561 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons, Flack and Wagner, Acta Cryst. B69 (2013) 249-259).
1 restraint	Absolute structure parameter: −0.3 (10)

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
C1	0.43869 (11)	0.3788 (5)	0.7633 (2)	0.0178 (4)
H1	0.3969	0.3330	0.8240	0.021*
N2	0.5000	0.3150 (7)	0.8427 (3)	0.0194 (5)
C3A	0.43517 (10)	0.5100 (5)	0.5945 (3)	0.0149 (3)
C3B	0.38810 (11)	0.6285 (5)	0.4558 (3)	0.0151 (4)
C3C	0.5000	0.5621 (7)	0.5250 (4)	0.0153 (5)
C4	0.31675 (11)	0.6519 (5)	0.4376 (3)	0.0188 (4)
H4	0.2877	0.5808	0.5303	0.023*
C11	0.28746 (10)	0.7760 (5)	0.2882 (3)	0.0221 (4)	0.5
H11	0.2386	0.7899	0.2769	0.027*	0.5
C6	0.32990 (11)	0.8802 (5)	0.1547 (3)	0.0215 (4)
H6	0.3087	0.9644	0.0518	0.026*
N5	0.28746 (10)	0.7760 (5)	0.2882 (3)	0.0221 (4)	0.5
C7	0.40193 (11)	0.8699 (5)	0.1610 (3)	0.0173 (4)
H7	0.4299	0.9462	0.0672	0.021*
C7A	0.43014 (9)	0.7411 (5)	0.3132 (3)	0.0139 (4)
N8	0.5000	0.6945 (6)	0.3610 (3)	0.0150 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0250 (11)	0.0155 (8)	0.0130 (9)	0.0004 (7)	0.0024 (7)	0.0020 (7)
N2	0.0302 (13)	0.0159 (10)	0.0122 (12)	0.000	0.000	0.0030 (9)
C3A	0.0192 (8)	0.0125 (7)	0.0128 (8)	0.0003 (7)	0.0010 (7)	−0.0001 (7)
C3B	0.0201 (9)	0.0126 (7)	0.0125 (8)	0.0003 (7)	0.0002 (7)	0.0002 (6)
C3C	0.0228 (13)	0.0115 (10)	0.0116 (12)	0.000	0.000	0.0024 (9)
C4	0.0188 (9)	0.0194 (9)	0.0183 (10)	0.0001 (8)	0.0042 (8)	−0.0013 (7)
C11	0.0213 (9)	0.0219 (8)	0.0232 (11)	0.0023 (7)	−0.0024 (8)	−0.0001 (8)
C6	0.0264 (11)	0.0177 (9)	0.0205 (10)	0.0046 (7)	−0.0074 (9)	−0.0018 (8)
N5	0.0213 (9)	0.0219 (8)	0.0232 (11)	0.0023 (7)	−0.0024 (8)	−0.0001 (8)
C7	0.0240 (10)	0.0136 (8)	0.0142 (9)	−0.0001 (7)	−0.0030 (8)	0.0018 (7)
C7A	0.0164 (8)	0.0122 (7)	0.0132 (9)	0.0008 (6)	−0.0007 (7)	−0.0008 (6)
N8	0.0167 (11)	0.0170 (10)	0.0114 (10)	0.000	0.000	0.0038 (9)

Geometric parameters (Å, º) top

C1—N2	1.356 (2)	C4—C11	1.370 (3)
C1—C3A	1.400 (3)	C4—H4	0.9500
C1—H1	0.9500	C11—C6	1.377 (3)
N2—C1ⁱ	1.356 (2)	C11—H11	0.9500
C3A—C3C	1.377 (2)	C6—C7	1.393 (3)
C3A—C3B	1.476 (3)	C6—H6	0.9500
C3B—C4	1.388 (3)	C7—C7A	1.387 (3)
C3B—C7A	1.435 (3)	C7—H7	0.9500
C3C—N8	1.365 (3)	C7A—N8	1.410 (2)
C3C—C3Aⁱ	1.377 (2)	N8—C7Aⁱ	1.410 (2)

N2—C1—C3A	121.9 (2)	C4—C11—C6	119.07 (18)
N2—C1—H1	119.0	C4—C11—H11	120.5
C3A—C1—H1	119.0	C6—C11—H11	120.5
C1ⁱ—N2—C1	121.7 (3)	C11—C6—C7	124.1 (2)
C3C—C3A—C1	111.8 (2)	C11—C6—H6	118.0
C3C—C3A—C3B	103.45 (19)	C7—C6—H6	118.0
C1—C3A—C3B	144.7 (2)	C7A—C7—C6	115.62 (19)
C4—C3B—C7A	117.71 (18)	C7A—C7—H7	122.2
C4—C3B—C3A	134.78 (19)	C6—C7—H7	122.2
C7A—C3B—C3A	107.51 (17)	C7—C7A—N8	130.0 (2)
N8—C3C—C3A	114.58 (13)	C7—C7A—C3B	122.38 (18)
N8—C3C—C3Aⁱ	114.58 (13)	N8—C7A—C3B	107.63 (19)
C3A—C3C—C3Aⁱ	130.8 (3)	C3C—N8—C7Aⁱ	106.83 (13)
C11—C4—C3B	121.14 (19)	C3C—N8—C7A	106.83 (13)
C11—C4—H4	119.4	C7Aⁱ—N8—C7A	146.3 (3)
C3B—C4—H4	119.4

Symmetry code: (i) −x+1, y, z.

(25NICz-2LT) top

Crystal data top

C₁₆H₉N₃	F(000) = 504
M_r = 243.26	D_x = 1.422 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 4.0049 (13) Å	Cell parameters from 924 reflections
b = 16.518 (5) Å	θ = 2.7–21.5°
c = 17.179 (5) Å	µ = 0.09 mm⁻¹
β = 90.007 (10)°	T = 300 K
V = 1136.5 (6) Å³	Plate, colourless
Z = 4	0.32 × 0.10 × 0.02 mm

Data collection top

Bruker KAPPA APEX II CCD diffractometer	997 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.088
ω– and φ–scans	θ_max = 25.2°, θ_min = 1.2°
Absorption correction: multi-scan SADABS	h = −4→4
T_min = 0.513, T_max = 0.745	k = −17→19
8439 measured reflections	l = −20→20
2027 independent reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.053	H-atom parameters constrained
wR(F²) = 0.147	w = 1/[σ²(F_o²) + (0.0626P)²] where P = (F_o² + 2F_c²)/3
S = 0.96	(Δ/σ)_max < 0.001
2027 reflections	Δρ_max = 0.25 e Å⁻³
174 parameters	Δρ_min = −0.22 e Å⁻³

Special details top

Refinement. Refined as a 2-component inversion twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
N2	0.7407 (16)	0.2344 (3)	0.36847 (18)	0.0714 (12)
N8	0.7512 (12)	0.2476 (2)	0.60015 (15)	0.0476 (8)
C1	0.8893 (14)	0.2978 (3)	0.4030 (2)	0.0675 (15)
H1	0.9843	0.3378	0.3720	0.081*
C3	0.5953 (13)	0.1755 (3)	0.4104 (2)	0.0683 (16)
H3	0.4941	0.1328	0.3842	0.082*
C3A	0.5899 (12)	0.1757 (3)	0.4916 (2)	0.0514 (13)
C3B	0.4757 (11)	0.1330 (2)	0.5620 (2)	0.0486 (11)
C3C	0.7452 (16)	0.2426 (3)	0.52047 (19)	0.0480 (9)
C4	0.3026 (11)	0.0614 (3)	0.5763 (3)	0.0608 (13)
H4	0.2343	0.0298	0.5344	0.073*
C11'	0.2307 (11)	0.0364 (3)	0.6499 (2)	0.0637 (17)	0.58 (4)
H11'	0.1174	−0.0119	0.6584	0.076*	0.58 (4)
C6	0.3277 (13)	0.0835 (3)	0.7107 (3)	0.0625 (14)
H6	0.2736	0.0661	0.7607	0.075*
N5	0.2307 (11)	0.0364 (3)	0.6499 (2)	0.0637 (17)	0.42 (4)
C7	0.5009 (12)	0.1553 (3)	0.7034 (2)	0.0509 (12)
H7	0.5632	0.1860	0.7464	0.061*
C7A	0.5768 (12)	0.1790 (3)	0.6276 (2)	0.0436 (12)
C9	1.0063 (12)	0.3515 (3)	0.6909 (2)	0.0526 (12)
H9	0.9457	0.3266	0.7373	0.063*
C8A	0.9256 (12)	0.3185 (2)	0.6197 (2)	0.0435 (12)
C10	1.1819 (12)	0.4236 (3)	0.6899 (3)	0.0614 (14)
H10	1.2374	0.4470	0.7374	0.074*
C11	1.2788 (11)	0.4624 (3)	0.6235 (2)	0.0687 (17)	0.42 (4)
H11	1.3945	0.5111	0.6259	0.082*	0.42 (4)
C12	1.2019 (12)	0.4280 (2)	0.5536 (3)	0.0627 (12)
H12	1.2706	0.4534	0.5080	0.075*
N5'	1.2788 (11)	0.4624 (3)	0.6235 (2)	0.0687 (17)	0.58 (4)
C12A	1.0252 (11)	0.3564 (2)	0.5485 (2)	0.0480 (11)
C12B	0.9066 (12)	0.3061 (3)	0.4842 (2)	0.0501 (12)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N2	0.091 (3)	0.079 (3)	0.044 (2)	0.013 (3)	−0.002 (2)	0.000 (2)
N8	0.0586 (18)	0.044 (2)	0.0406 (19)	0.0018 (15)	0.002 (3)	0.000 (2)
C1	0.078 (4)	0.076 (4)	0.049 (3)	0.012 (3)	0.011 (3)	0.010 (3)
C3	0.077 (4)	0.080 (4)	0.047 (3)	0.014 (3)	−0.010 (2)	−0.010 (3)
C3A	0.059 (3)	0.056 (3)	0.039 (3)	0.011 (2)	−0.009 (2)	−0.008 (2)
C3B	0.049 (3)	0.047 (3)	0.050 (2)	0.010 (2)	−0.005 (2)	−0.008 (2)
C3C	0.058 (2)	0.057 (3)	0.028 (2)	0.010 (2)	0.004 (3)	0.003 (2)
C4	0.051 (3)	0.061 (3)	0.071 (3)	0.003 (3)	−0.009 (3)	−0.019 (3)
C11'	0.061 (3)	0.056 (4)	0.074 (3)	0.003 (2)	0.004 (3)	−0.006 (3)
C6	0.067 (4)	0.059 (3)	0.061 (3)	0.006 (3)	0.011 (2)	0.012 (3)
N5	0.061 (3)	0.056 (4)	0.074 (3)	0.003 (2)	0.004 (3)	−0.006 (3)
C7	0.056 (3)	0.050 (3)	0.046 (2)	0.009 (3)	−0.003 (2)	0.004 (2)
C7A	0.045 (3)	0.042 (3)	0.044 (3)	0.008 (2)	0.000 (2)	−0.002 (2)
C9	0.055 (3)	0.054 (3)	0.048 (2)	0.008 (3)	0.000 (3)	−0.003 (2)
C8A	0.046 (3)	0.040 (3)	0.044 (2)	0.006 (2)	0.001 (2)	−0.002 (2)
C10	0.063 (3)	0.054 (3)	0.067 (3)	−0.001 (3)	−0.008 (3)	−0.010 (3)
C11	0.067 (3)	0.057 (3)	0.082 (3)	−0.006 (3)	−0.001 (3)	0.000 (3)
C12	0.057 (3)	0.054 (3)	0.077 (3)	0.003 (2)	0.011 (3)	0.013 (3)
N5'	0.067 (3)	0.057 (3)	0.082 (3)	−0.006 (3)	−0.001 (3)	0.000 (3)
C12A	0.049 (3)	0.044 (3)	0.051 (3)	0.007 (2)	0.007 (2)	0.010 (2)
C12B	0.054 (3)	0.062 (3)	0.035 (2)	0.014 (2)	0.002 (2)	0.005 (2)

Geometric parameters (Å, º) top

N2—C3	1.343 (6)	C11'—H11'	0.9300
N2—C1	1.343 (6)	C6—C7	1.380 (6)
N8—C3C	1.371 (4)	C6—H6	0.9300
N8—C8A	1.405 (5)	C7—C7A	1.394 (5)
N8—C7A	1.411 (6)	C7—H7	0.9300
C1—C12B	1.404 (5)	C9—C8A	1.377 (5)
C1—H1	0.9300	C9—C10	1.382 (6)
C3—C3A	1.396 (5)	C9—H9	0.9300
C3—H3	0.9300	C8A—C12A	1.431 (5)
C3A—C3C	1.361 (7)	C10—C11	1.364 (5)
C3A—C3B	1.472 (6)	C10—H10	0.9300
C3B—C4	1.394 (6)	C11—C12	1.365 (5)
C3B—C7A	1.418 (5)	C11—H11	0.9300
C3C—C12B	1.381 (7)	C12—C12A	1.380 (6)
C4—C11'	1.360 (5)	C12—H12	0.9300
C4—H4	0.9300	C12A—C12B	1.461 (6)
C11'—C6	1.360 (6)

C3—N2—C1	121.4 (4)	C6—C7—C7A	115.9 (4)
C3C—N8—C8A	107.3 (4)	C6—C7—H7	122.0
C3C—N8—C7A	106.0 (4)	C7A—C7—H7	122.0
C8A—N8—C7A	146.6 (3)	C7—C7A—N8	130.2 (4)
N2—C1—C12B	122.5 (5)	C7—C7A—C3B	122.0 (4)
N2—C1—H1	118.8	N8—C7A—C3B	107.8 (3)
C12B—C1—H1	118.8	C8A—C9—C10	116.7 (4)
N2—C3—C3A	122.7 (5)	C8A—C9—H9	121.6
N2—C3—H3	118.6	C10—C9—H9	121.6
C3A—C3—H3	118.6	C9—C8A—N8	131.3 (4)
C3C—C3A—C3	111.0 (4)	C9—C8A—C12A	121.3 (4)
C3C—C3A—C3B	103.4 (3)	N8—C8A—C12A	107.4 (3)
C3—C3A—C3B	145.5 (5)	C11—C10—C9	124.0 (4)
C4—C3B—C7A	117.2 (4)	C11—C10—H10	118.0
C4—C3B—C3A	135.0 (4)	C9—C10—H10	118.0
C7A—C3B—C3A	107.9 (3)	C10—C11—C12	118.4 (4)
C3A—C3C—N8	114.8 (4)	C10—C11—H11	120.8
C3A—C3C—C12B	131.8 (3)	C12—C11—H11	120.8
N8—C3C—C12B	113.3 (5)	C11—C12—C12A	121.8 (4)
C11'—C4—C3B	121.8 (4)	C11—C12—H12	119.1
C11'—C4—H4	119.1	C12A—C12—H12	119.1
C3B—C4—H4	119.1	C12—C12A—C8A	117.6 (4)
C6—C11'—C4	118.7 (4)	C12—C12A—C12B	134.5 (4)
C6—C11'—H11'	120.7	C8A—C12A—C12B	107.9 (4)
C4—C11'—H11'	120.7	C3C—C12B—C1	110.5 (5)
C11'—C6—C7	124.4 (4)	C3C—C12B—C12A	104.1 (3)
C11'—C6—H6	117.8	C1—C12B—C12A	145.4 (5)
C7—C6—H6	117.8

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C7—H7···N2ⁱ	0.93	2.58	3.505 (6)	178
C9—H9···N2ⁱ	0.93	2.60	3.529 (6)	176

Symmetry code: (i) x, −y+1/2, z+1/2.

(2NICz-2HT) top

Crystal data top

C₁₆H₉N₃	D_x = 1.402 Mg m⁻³
M_r = 243.26	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pccn	Cell parameters from 165 reflections
a = 4.0741 (8) Å	θ = 2.4–20.2°
b = 16.416 (3) Å	µ = 0.09 mm⁻¹
c = 17.230 (3) Å	T = 380 K
V = 1152.3 (4) Å³	Plate, colourless
Z = 4	0.32 × 0.10 × 0.02 mm
F(000) = 504

Data collection top

Bruker KAPPA APEX II CCD diffractometer	393 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.056
ω– and φ–scans	θ_max = 24.7°, θ_min = 2.4°
Absorption correction: multi-scan SADABS	h = −2→4
T_min = 0.609, T_max = 0.745	k = −15→18
2369 measured reflections	l = −15→19
971 independent reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.050	H-atom parameters constrained
wR(F²) = 0.152	w = 1/[σ²(F_o²) + (0.0662P)²] where P = (F_o² + 2F_c²)/3
S = 0.93	(Δ/σ)_max < 0.001
971 reflections	Δρ_max = 0.13 e Å⁻³
88 parameters	Δρ_min = −0.18 e Å⁻³

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
N2	0.7500	0.2500	0.3695 (3)	0.1074 (18)
N8	0.7500	0.2500	0.5998 (2)	0.0639 (12)
C1	0.6010 (13)	0.1889 (2)	0.4070 (2)	0.1008 (15)
H1	0.5008	0.1478	0.3784	0.121*
C3A	0.5919 (10)	0.1852 (2)	0.4884 (2)	0.0720 (11)
C3B	0.4723 (9)	0.1391 (2)	0.5555 (2)	0.0682 (10)
C3C	0.7500	0.2500	0.5204 (3)	0.0694 (15)
C4	0.2994 (10)	0.0670 (2)	0.5649 (3)	0.0890 (12)
H4	0.2347	0.0378	0.5212	0.107*
C11	0.2222 (9)	0.03797 (19)	0.6366 (3)	0.0984 (13)	0.5
H5	0.1033	−0.0100	0.6422	0.118*	0.5
C6	0.3222 (10)	0.0805 (2)	0.6996 (2)	0.0890 (13)
H6	0.2701	0.0598	0.7483	0.107*
N5	0.2222 (9)	0.03797 (19)	0.6366 (3)	0.0984 (13)	0.5
C7	0.4968 (9)	0.15264 (19)	0.69632 (19)	0.0705 (10)
H2	0.5574	0.1808	0.7409	0.085*
C7A	0.5757 (9)	0.18040 (18)	0.62332 (17)	0.0617 (10)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N2	0.117 (5)	0.138 (4)	0.067 (4)	0.016 (4)	0.000	0.000
N8	0.072 (3)	0.063 (2)	0.056 (3)	0.003 (2)	0.000	0.000
C1	0.109 (4)	0.121 (4)	0.071 (3)	0.021 (3)	−0.016 (3)	−0.024 (2)
C3A	0.069 (3)	0.091 (2)	0.056 (2)	0.016 (2)	−0.008 (2)	−0.017 (2)
C3B	0.064 (3)	0.071 (2)	0.070 (2)	0.0104 (19)	−0.009 (2)	−0.011 (2)
C3C	0.088 (5)	0.081 (3)	0.040 (3)	0.017 (3)	0.000	0.000
C4	0.068 (3)	0.088 (3)	0.111 (3)	0.006 (3)	−0.010 (3)	−0.034 (3)
C11	0.089 (3)	0.079 (2)	0.127 (3)	−0.003 (2)	0.008 (3)	−0.007 (2)
C6	0.084 (3)	0.080 (2)	0.103 (3)	0.010 (2)	0.010 (3)	0.013 (2)
N5	0.089 (3)	0.079 (2)	0.127 (3)	−0.003 (2)	0.008 (3)	−0.007 (2)
C7	0.074 (3)	0.0681 (19)	0.069 (2)	0.008 (2)	−0.002 (2)	0.0056 (18)
C7A	0.065 (3)	0.0607 (18)	0.060 (2)	0.0044 (18)	0.001 (2)	0.0024 (18)

Geometric parameters (Å, º) top

N2—C1	1.339 (5)	C3B—C7A	1.415 (4)
N2—C1ⁱ	1.339 (5)	C3C—C3Aⁱ	1.361 (4)
N8—C3C	1.368 (5)	C4—C11	1.362 (4)
N8—C7Aⁱ	1.405 (3)	C4—H4	0.9300
N8—C7A	1.405 (3)	C11—C6	1.353 (4)
C1—C3A	1.404 (4)	C11—H5	0.9300
C1—H1	0.9300	C6—C7	1.383 (4)
C3A—C3C	1.361 (4)	C6—H6	0.9300
C3A—C3B	1.465 (4)	C7—C7A	1.376 (4)
C3B—C4	1.387 (4)	C7—H2	0.9300

C1—N2—C1ⁱ	122.2 (5)	C11—C4—C3B	121.4 (4)
C3C—N8—C7Aⁱ	106.78 (19)	C11—C4—H4	119.3
C3C—N8—C7A	106.78 (19)	C3B—C4—H4	119.3
C7Aⁱ—N8—C7A	146.4 (4)	C6—C11—C4	118.6 (4)
N2—C1—C3A	121.8 (4)	C6—C11—H5	120.7
N2—C1—H1	119.1	C4—C11—H5	120.7
C3A—C1—H1	119.1	C11—C6—C7	124.3 (4)
C3C—C3A—C1	111.0 (4)	C11—C6—H6	117.8
C3C—C3A—C3B	104.0 (3)	C7—C6—H6	117.8
C1—C3A—C3B	145.1 (4)	C7A—C7—C6	116.2 (3)
C4—C3B—C7A	117.6 (3)	C7A—C7—H2	121.9
C4—C3B—C3A	134.5 (4)	C6—C7—H2	121.9
C7A—C3B—C3A	107.8 (3)	C7—C7A—N8	130.6 (3)
C3Aⁱ—C3C—C3A	132.2 (5)	C7—C7A—C3B	121.8 (3)
C3Aⁱ—C3C—N8	113.9 (2)	N8—C7A—C3B	107.5 (3)
C3A—C3C—N8	113.9 (2)

Symmetry code: (i) −x+3/2, −y+1/2, z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C7—H2···N2ⁱⁱ	0.93	2.61	3.538 (5)	176

Symmetry code: (ii) x, −y+1/2, z+1/2.

Acknowledgements

The authors thank Werner Artner for performing the low-temperature powder X-ray diffraction experiments.

Funding information

TK, JF and PK gratefully acknowledge financial support by the Austrian Science Fund (FWF) (grant No. I 2589-N34).

References

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research papers\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

The phase transitions of 4-amino­pyridine-based indolocarbazoles: twinning, local- and pseudo-symmetry

1. Introduction

2. Experimental

2.1. Synthesis and crystal growth

2.2. Data collection and refinement

2.2.1. General

2.2.2. Details for 5NICz

2.2.3. Details for 2NICz, 2,5NICz-2LT and 2,5NICz-2HT

2.2.4. Details for 2,5NICz-1

2.3. X-ray powder diffraction

3. Results and discussion

3.1. The OD polytypism of 5NICz

3.1.1. Local symmetry

3.1.2. Stacking possibilities

3.1.3. Maximum degree of order (MDO) polytypes

3.1.4. Twinning

3.1.5. Desymmetrization and metric parameters

3.1.6. Structural changes on phase transition

3.2. Phase transitions of 2NICz, and 2,5NICz-2LT and 2,5NICz-2HT polymorphs

3.2.1. Symmetry relationships

3.2.2. Twinning

3.2.3. Desymmetrization

3.2.4. Crystal chemistry

3.3. 2,5NICz-1

3.4. Powder diffraction

4. Conclusion

Supporting information

Acknowledgements

Funding information

References

research papers

The phase transitions of 4-aminopyridine-based indolocarbazoles: twinning, local- and pseudo-symmetry