Crystal structure of poly[tetra­kis­(4-methyl­anilin­ium) [octa-μ-chlorido-di­chlorido­tricadmium(II)]]: a two-dimensional organic–inorganic hybrid perovskite

Subashini, A.; Crochet, A.; Ramamurthi, K.; Ramesh Babu, R.; Stoeckli-Evans, H.

doi:10.1107/S2056989022010830

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ISSN: 2056-9890

Volume 78| Part 12| December 2022| Pages 1223-1227

https://doi.org/10.1107/S2056989022010830

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Crystal structure of poly[tetrakis(4-methylanilinium) [octa-μ-chlorido-dichloridotricadmium(II)]]: a two-dimensional organic–inorganic hybrid perovskite

A. Subashini,^a,^b ^* Aurelien Crochet,^c K. Ramamurthi,^b R. Ramesh Babu ^b and Helen Stoeckli-Evans ^d ^*

^aPG and Research Department of Physics, SrimadAndavan Arts and Science College, Tiruchirappalli - 620 005, India, ^bCrystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli - 620 024, India, ^cChemistry Department, University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg, Switzerland, and ^dInstitute of Physics, University of Neuchâtel, rue Emile-Argand 11, 2000 Neuchâtel, Switzerland
^*Correspondence e-mail: viji.suba@gmail.com, helen.stoeckli-evans@unine.ch

Edited by W. T. A. Harrison, University of Aberdeen, United Kingdom (Received 1 November 2022; accepted 11 November 2022; online 17 November 2022)

The title polymeric compound, (C₇H₁₀N)₄[Cd₃Cl₁₀], involves a centrosymmetric [Cd₃Cl₁₀]⁴⁻ tetra-anion, which is made up of three face-sharing CdCl₆ octahedra, linked by four corner Cl atoms, forming layers propagating in the ab plane. The p-methylanilinium cations, situated between the layers, form N—H⋯Cl hydrogen bonds to the layers, which stack up the c-axis direction. There are no π–π or C—H⋯π interactions involving the aromatic rings, which are inclined to each other by 42.3 (1) ° in the asymmetric unit.

Keywords: crystal structure; cadmium; two-dimensional perovskite; hydrogen bonding.

CCDC reference: 922195

1. Chemical context

There are numerous reports of the structures of polymeric structures involving transition metal halide networks with organic cations to provide charge compensation [Cambridge Structural Database (CSD), Version 5.43, last update September 2022; Groom et al., 2016 ]. They include a number of layer-like structures that have been described as organic–inorganic two-dimensional hybrid perovskites. The structure, properties and applications, especially optoelectronic applications, of such compounds have been reviewed recently by Zhu and collaborators (Zhang et al., 2020 ).

Beatty and collaborators (Costin-Hogan et al., 2008 ) reported on a number of complexes formed by the reaction of ortho-substituted phenylamines with cadmium halide salts. They showed, for example, that the reaction of an acidified solution in methanol of CdCl₂ with aniline led to the formation of the [Cd₃Cl₁₀]^4– linear tetra-anion in the compound poly-[tetrakis(anilinium) [decachlorotricadmium(II)]] (CSD refcode EGUFUI). In the present work an analogous reaction has been studied using a para-substituted derivative of aniline, 4-methylaniline. The resulting structure of the title compound, (I), is isostructural with that of EGUFUI.

A search of the CSD for polymeric compounds involving the title cation, 4-methylanilinium, gave only four hits. One in particular is of interest, namely bis(4-methylanilinium) pentamolybdate (YIKLIP; Oszajca et al., 2013 ), whose structure was determined by powder X-ray diffraction analysis. It is composed of layers of inorganic {[Mo₅O₁₆]^2–}_n polyanions alternating with layers of 4-methylanilinium cations. The latter are linked to the inorganic polyanions by N—H⋯O hydrogen bonds, involving both terminal and shared O atoms.

2. Structural commentary

The asymmetric unit of the title compound, {[Cd₃Cl₁₀]⁴⁻·4[(C₇H₁₀N)⁺]}_n (I), is composed of half of a centrosymmetric [Cd₃Cl₁₀]^4– tetra-anion, with the central Cd2 atom being situated on a crystallographic inversion centre, and two 4-methylanilinium cations (Fig. 1). The complete [Cd₃Cl₁₀]^4– unit is made up of three face sharing CdCl₆ octahedra. They are linked by four corner Cl⁻ ions (Cl2, Cl2ⁱ, Cl2^iv and Cl2^v; Fig. 1) to form a layer-like structure lying parallel to the ab plane (Figs. 2 and 3). The octahedral environment of atom Cd1 is slightly distorted with one short contact to a terminal Cl atom (Cl1) of 2.5051 (5) Å, while the other five Cd—Cl bond lengths vary from 2.6329 (5) to 2.7220 (5) Å. The Cd2—Cl bond lengths vary from 2.5764 (5) to 2.6750 (4) Å (Table 1). The cadmium atoms are separated by 3.4082 (2) Å. These bond lengths and the metal⋯metal distance are very similar to those observed for the three compounds involving cadmium chloride mentioned below in § 6. Database survey.

Table 1
Selected bond lengths (Å)

Cd1—Cl1	2.5051 (5)	Cd1—Cl5	2.6511 (5)
Cd1—Cl2	2.6560 (5)	Cd2—Cl3	2.6750 (4)
Cd1—Cl2ⁱ	2.6329 (5)	Cd2—Cl4	2.6551 (4)
Cd1—Cl3	2.6462 (5)	Cd2—Cl5	2.5764 (5)
Cd1—Cl4	2.7220 (5)
Symmetry code: (i) $[-x+{\script{3\over 2}}, y-{\script{1\over 2}}, z]$ .

Figure 1
A view of the structure of the polymeric unit of compound I. The displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) −x + 1, −y + 2, −z; (ii) x − $[{1\over 2}]$ , −y + $[{3\over 2}]$ , −z; (iii) −x + $[{3\over 2}]$ , y + $[{1\over 2}]$ , z; (iv) x − $[{1\over 2}]$ , −y + $[{5\over 2}]$ , −z; (v) −x + $[{3\over 2}]$ , y − $[{1\over 2}]$ , z.]

Figure 2
A view along the c-axis of the layer-like structure of the [Cd₃Cl₁₀]⁴⁻ polymeric arrangement in I. Colour code: Cd yellow, Cl green.

Figure 3
A view along the b-axis of the crystal packing of compound I. The N—H⋯Cl hydrogen bonds (see Table 2

) are shown as dashed lines. For clarity, the C-bound H atoms have been omitted. Colour code as in Fig. 2

The two p-methylanilinium cations lie in the interstitial space between the layers (Fig. 3). They have normal geometry, with the heteroatoms of each cation being almost coplanar with their attached rings: cation N1/C1–C7 is almost planar (r.m.s. deviation = 0.009 Å) with atoms N1 and C7 both being displaced from the mean plane by 0.011 (2) Å; cation N2/C8–C14 is slightly less planar (r.m.s. deviation = 0.047 Å) with N2 and C14 being displaced from the mean plane by 0.064 (2) and 0.060 (3) Å, respectively.

3. Supramolecular features

In the crystal of I, the p-methylanilinium cations that are situated between the layers are N—H⋯Cl hydrogen bonded to the front and back of the layers that stack up the c-axis (Fig. 3). All six ammonium H atoms are involved in hydrogen bonding with all five chloride ions (Table 2). However, there are no identified π–π or C—H⋯π interactions involving the aromatic rings (C1–C6 and C8–C13) of the p-methylanilinium cations. The rings are inclined to each other by 42.3 (1) ° in the asymmetric unit and by ca 71.8 and 73.8°, respectively, to the ab plane in which lies the anionic {[Cd₃Cl₁₀]⁴⁻}_n layer-like structure.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1AN⋯Cl5ⁱⁱ	0.86 (3)	2.42 (3)	3.258 (2)	166 (2)
N1—H1BN⋯Cl2ⁱⁱⁱ	0.91 (3)	2.38 (3)	3.236 (2)	158 (3)
N1—H1CN⋯Cl4^iv	0.80 (3)	2.70 (3)	3.360 (2)	141 (3)
N2—H2AN⋯Cl3^v	0.87 (3)	2.34 (3)	3.198 (2)	170 (3)
N2—H2BN⋯Cl1^vi	0.85 (3)	2.48 (3)	3.273 (2)	156 (2)
N2—H2CN⋯Cl1^vii	0.93 (4)	2.29 (4)	3.194 (2)	164 (3)
Symmetry codes: (ii) ; (iii) $[x-{\script{1\over 2}}, -y+{\script{3\over 2}}, -z]$ ; (iv) ; (v) $[x-{\script{1\over 2}}, y-1, -z+{\script{1\over 2}}]$ ; (vi) $[x-{\script{1\over 2}}, y, -z+{\script{1\over 2}}]$ ; (vii) $[-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

4. Thermal analyses

Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) were recorded in the temperature range 25–650°C, at a heating rate of 10°C min⁻¹ under a nitrogen atmosphere, using an SDT Q600 simultaneous thermo analytical system. The alumina crucible was loaded with 6.191 mg of compound I. It can be seen in the TGA and DTA curves for I (Fig. 4), that the sample begins to decompose before reaching the melting point. In the TGA curve, the first weight loss (198–216°C) is due to the loss of two methylanilinium cations and two chloride anions: calculated 25.5%, observed 24.8%. The second weight loss (216–250°C) is due to the loss of the two remaining methylanilinium cations: calculated 19.2%, observed 18.2%. The third weight loss (553–559°C) involves the loss of two equivalents of HCl: calculated 6.3%, experimental 6.3%. The residual cadmium chloride (CdCl₂) begins to evaporate at 559°C as observed from the DTA curve (Fig. 4), and it continues slowly up to 650°C. There is a small residue (0.83%) remaining at 650°C.

Figure 4
The TGA (blue) and DTA (black) curves for I.

5. FT–IR and FT–Raman spectroscopy

A Perkin Elmer-paragon-500 Fourier transform infrared (FT–IR) was used to record the FT–IR spectrum (KBr pellet) in the wavelength range of 450–4000 cm⁻¹. A Varian FT–Raman spectrometer was used to record the FT–Raman spectrum in the wavelength range 400–4000 cm⁻¹.

The FT–IR and FT–Raman spectra of I are illustrated in Fig. 5, and the assignment of the vibrational frequencies are presented in Table 3. The intermolecular N—H⋯Cl stretching vibration is observed at 3129 cm⁻¹ (FT–IR) and 3126 cm⁻¹ (FT–Raman) (Haigh et al., 1967 ). The band at 637 cm⁻¹ in the FT–IR and 638 cm⁻¹ in the FT–Raman corresponds to the NH₂ twisting frequency. The asymmetric NH stretching frequency is observed at 3510 cm⁻¹ in the FT–IR spectrum. The peak at 1243 cm⁻¹ in the FT–IR spectrum is due to the C—N vibration. The frequencies of the FT–IR spectrum agree well with the corresponding values of the FT–Raman spectrum and also when compared with those of p-methylaniline (Altun et al., 2003 ).

Table 3
Assignment of FT–IR and FT–Raman vibrational frequencies (cm⁻¹) for I and p-methylaniline

	FT–IR		FT–Raman
Assignment of vibrational frequencies	I	p-methylaniline^a	I	p-methylaniline^b
ν (NH) asymmetric	3510	3416	-	3418
γ NH₂ (twisting)	637	-	638	-
β NH₂ (scis.)	1616	1621	1608	1617
β CH₃ sym	1391	-	1380	1380
γ CH₃ sym	2881	2912	2922	2917
ν (C=C) aromatic	1560, 1503, 1291	1582, 1514, 1441	-	1581, 1281
β (C—H) 1,4-disubstituted	1190, 1114	1176, 1120	1196	1179
ν (C—N)	1243	1267	-	1271
ν (N—H⋯Cl) intermolecular	3129	-	3126	-
Notes: (a) Haigh et al. (1967);(b) Altun et al. (2003).

Figure 5
FT–IR and FT–Raman spectra for I.

6. Database survey

A search of the Cambridge Structural Database (CSD, Version 5.43, last update September 2022; Groom et al., 2016) for polymeric-type structures involving transition-metal halide salts with organic cations gave over 150 hits. The large majority involve cadmium halide salts forming zero-dimensional (molecular) salts or one-dimensional polymer chains.

There are only four reports of two-dimensional layered perovskite-type compounds involving the same [Cd₃X₁₀]^4– (where X = Br, Cl) linear tetra-anion as in the title compound I. They include: catena-[tetrakis(anilinium) [octakis(μ₂-bromo)dibromotricadmium]] (CSD refcode POPHAD; Ishihara et al., 1994 ), catena-[tetrakis(anilinium) [octakis(μ₂-chloro)dichlorotricadmium(II)]] (EGUFUI; Costin-Hogan et al., 2008), catena-[tetrakis(isopropylammonium) [decachlorotricadmium(II)]] (IPEMAS01; Gagor et al., 2011 ) and catena-[tetrakis(cyclopentanaminium) [octakis(μ-chloro)dichlorotricadmium(II)]] (QOHGUR; Liao et al., 2014 ). The various Cd—Cl bond lengths, involving atoms Cd1 and Cd2, for the three compounds are similar to those observed for I, as seen in Table 4. The Cd1⋯Cd2 interatomic distance for I [3.4082 (2) Å] however, is shorter than that observed in the other three compounds; see Table 4.

Table 4
A comparison of selected geometrical parameters (Å) for I, EGUFUI^a, IPEMAS01^b and QOHGUR^c

Distances	I	EGUFUI^a	IPEMAS01^b	QOHGUR^c
Cd1—Cl1	2.5051 (5)	2.4962 (9)	2.4880 (7)	2.496 (2)
Cd1—Cl(2,3,4,5)	2.6329 (5)–2.7220 (5)	2.5882 (9)–2.8926 (9)	2.6218 (7)–2.7404 (6)	2.660 (2)–2.763 (2)
Cd2^d—Cl(3,4,5)	2.5764 (5)–2.6750 (4)	2.5632 (9)–2.7391 (9)	2.5795 (6)–2.6903 (6)	2.577 (2)–2.697 (2)
Cd1⋯Cd2^d	3.4082 (2)	3.4714 (6)	3.4493 (3)	3.4396 (9)
Notes: (a) Costin-Hogan et al. (2008); (b) Gagor et al. (2011); (c) Liao et al. (2014); (d) Atom Cd2 is located on an inversion centre

All four compounds crystallize at room temperature in the orthorhombic space group Pbca, as does the title compound (I). Hence, all five compounds are isostructural. As noted by Gagor et al. (2011) and Liao et al. (2014), some layered organic–inorganic hybrids have been shown to show reversible structural phase transitions because cooling and heating can induce reorientation of the organic cations and deformation of the anionic framework. Such changes were observed for compounds IPEMASS01 and QOHGUR, which undergo two phase transitions. At low temperature they transform into the non-centrosymmetric orthorhombic space group P2₁2₁2₁ [structures IPEMAS02 (275 K) and QOHGUR01 (93 K)], while at high temperature they transform to the centrosymmetric orthorhombic space group Cmca [structures IPEMAS (320 K) and QOHGUR02 (343 K)]. As reported by Gagor et al. (2011), the transition from Pbca to P2₁2₁2₁ is type I: translationengleiche; the crystal class changes from mmm to 222. The change from Cmca to Pbca is type IIA: klassengleiche; the crystal class does not change (mmm to mmm). For further details concerning subgroups and supergroups of space groups, see Müller (2013 ).

7. Synthesis and crystallization

Concentrated HCl (1 ml) was added dropwise to a mixture of cadmium chloride dihydrate (1 g, 0.009 mol) and p-methylaniline (1.71 g, 0.009 mol) in methanol (30 ml) until the solution was clear. The solution was then stirred and heated under reflux at 353 K for 6 h and filtered. The solution was allowed to evaporate slowly at room temperature, yielding small, orange block-like crystals of I after ca 21 days.

8. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 5. The ammonium H atoms were located in difference-Fourier maps and freely refined. The C-bound H atoms were included in calculated positions (C—H = 0.95 Å) and treated as riding atoms with U_iso(H) = 1.2U_eq(C). The average hkl measurement multiplicity was low, hence an empirical absorption correction was applied.

Table 5
Experimental details

Crystal data
Chemical formula	(C₇H₁₀N)₄[Cd₃Cl₁₀]
M_r	1124.34
Crystal system, space group	Orthorhombic, Pbca
Temperature (K)	200
a, b, c (Å)	19.4883 (7), 7.3754 (3), 27.1557 (10)
V (Å³)	3903.2 (3)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	2.33
Crystal size (mm)	0.12 × 0.10 × 0.08

Data collection
Diffractometer	STOE IPDS 2T
Absorption correction	Empirical (using intensity measurements) (ShxAbs; Spek, 2020 )
T_min, T_max	0.495, 0.839
No. of measured, independent and observed [I > 2σ(I)] reflections	49498, 3681, 3072
R_int	0.040
(sin θ/λ)_max (Å⁻¹)	0.609

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.015, 0.031, 0.95
No. of reflections	3681
No. of parameters	231
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.22, −0.35
Computer programs: X-AREA and X-RED32 (Stoe & Cie, 2009 ), SHELXS97 (Sheldrick, 2008 ), SHELXL2018/3 (Sheldrick, 2015 ), PLATON (Spek, 2020), Mercury (Macrae et al., 2020 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 922195

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S2056989022010830/hb8044sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989022010830/hb8044Isup2.hkl

TGA/DSC instrument trace. DOI: https://doi.org/10.1107/S2056989022010830/hb8044sup3.tif

checkCIF report

Computing details top

Data collection: X-AREA (Stoe & Cie, 2009); cell refinement: X-AREA (Stoe & Cie, 2009); data reduction: X-RED32 (Stoe & Cie, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2020) and Mercury (Macrae et al., 2020); software used to prepare material for publication: SHELXL2018/3 (Sheldrick, 2015), PLATON (Spek, 2020) and publCIF (Westrip, 2010).

Poly[tetrakis(4-methylanilinium) [octa-µ-chlorido-dichloridotricadmium(II)]] top

Crystal data top

(C₇H₁₀N)₄[Cd₃Cl₁₀]	D_x = 1.913 Mg m⁻³
M_r = 1124.34	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 42237 reflections
a = 19.4883 (7) Å	θ = 1.5–26.1°
b = 7.3754 (3) Å	µ = 2.33 mm⁻¹
c = 27.1557 (10) Å	T = 200 K
V = 3903.2 (3) Å³	Block, orange
Z = 4	0.12 × 0.10 × 0.08 mm
F(000) = 2200

Data collection top

STOE IPDS 2T diffractometer	3681 independent reflections
Radiation source: fine-focus sealed tube	3072 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.040
Detector resolution: 6.67 pixels mm^-1	θ_max = 25.7°, θ_min = 1.5°
rotation method scans	h = −23→23
Absorption correction: empirical (using intensity measurements) (ShxAbs; Spek, 2020)	k = −8→9
T_min = 0.495, T_max = 0.839	l = −32→33
49498 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.015	Hydrogen site location: mixed
wR(F²) = 0.031	H atoms treated by a mixture of independent and constrained refinement
S = 0.95	w = 1/[σ²(F_o²) + (0.019P)²] where P = (F_o² + 2F_c²)/3
3681 reflections	(Δ/σ)_max = 0.001
231 parameters	Δρ_max = 0.22 e Å⁻³
0 restraints	Δρ_min = −0.34 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.

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

	x	y	z	U_iso*/U_eq
Cd1	0.65796 (2)	0.94295 (2)	0.05158 (2)	0.02163 (4)
Cd2	0.500000	1.000000	0.000000	0.02469 (5)
Cl1	0.68348 (3)	0.90247 (7)	0.14132 (2)	0.03240 (11)
Cl2	0.75872 (2)	1.17278 (6)	0.03058 (2)	0.02941 (11)
Cl3	0.56591 (2)	1.20044 (6)	0.06710 (2)	0.02527 (10)
Cl4	0.54771 (2)	0.71648 (6)	0.04958 (2)	0.02671 (10)
Cl5	0.61915 (2)	0.99188 (6)	−0.04104 (2)	0.02448 (10)
N1	0.37129 (12)	0.5701 (3)	0.02703 (7)	0.0315 (4)
H1AN	0.3750 (13)	0.686 (4)	0.0249 (9)	0.053 (8)*
H1BN	0.3360 (18)	0.533 (4)	0.0078 (13)	0.083 (11)*
H1CN	0.4063 (17)	0.527 (4)	0.0167 (11)	0.062 (10)*
C1	0.35738 (10)	0.5140 (2)	0.07793 (7)	0.0244 (4)
C2	0.29246 (10)	0.5348 (3)	0.09622 (8)	0.0311 (5)
H2	0.256915	0.583871	0.076329	0.037*
C3	0.27966 (11)	0.4828 (3)	0.14427 (8)	0.0361 (5)
H3	0.234749	0.495974	0.157397	0.043*
C4	0.33130 (11)	0.4116 (3)	0.17363 (7)	0.0316 (5)
C5	0.39604 (11)	0.3939 (3)	0.15362 (8)	0.0327 (5)
H5	0.432061	0.346507	0.173362	0.039*
C6	0.40968 (10)	0.4435 (3)	0.10564 (8)	0.0304 (4)
H6	0.454307	0.429046	0.092124	0.036*
C7	0.31785 (14)	0.3573 (3)	0.22625 (8)	0.0495 (6)
H7A	0.304491	0.229302	0.227434	0.074*
H7B	0.280746	0.432013	0.239740	0.074*
H7C	0.359564	0.375359	0.245799	0.074*
N2	0.15463 (12)	0.4659 (3)	0.36493 (7)	0.0346 (4)
H2AN	0.1309 (15)	0.405 (4)	0.3864 (11)	0.061 (9)*
H2BN	0.1564 (14)	0.578 (4)	0.3724 (10)	0.055 (8)*
H2CN	0.1999 (19)	0.426 (4)	0.3665 (12)	0.082 (11)*
C8	0.12388 (11)	0.4504 (3)	0.31563 (7)	0.0290 (4)
C9	0.15310 (12)	0.3358 (3)	0.28179 (8)	0.0375 (5)
H9	0.191036	0.261630	0.290563	0.045*
C10	0.12627 (13)	0.3304 (3)	0.23464 (8)	0.0417 (5)
H10	0.146815	0.252891	0.210894	0.050*
C11	0.07051 (12)	0.4343 (3)	0.22117 (8)	0.0370 (5)
C12	0.04108 (12)	0.5428 (3)	0.25683 (9)	0.0442 (6)
H12	0.001676	0.612632	0.248775	0.053*
C13	0.06764 (12)	0.5523 (3)	0.30399 (9)	0.0413 (5)
H13	0.047045	0.628683	0.327979	0.050*
C14	0.04386 (15)	0.4313 (4)	0.16891 (9)	0.0542 (7)
H14A	−0.004455	0.468112	0.168625	0.081*
H14B	0.048053	0.308410	0.155525	0.081*
H14C	0.070716	0.515440	0.148688	0.081*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cd1	0.02012 (7)	0.02084 (7)	0.02392 (7)	0.00165 (5)	−0.00197 (6)	0.00028 (5)
Cd2	0.01681 (9)	0.02408 (9)	0.03317 (11)	−0.00019 (7)	−0.00311 (8)	−0.00007 (8)
Cl1	0.0366 (3)	0.0388 (3)	0.0218 (2)	−0.0015 (2)	−0.0016 (2)	−0.00037 (19)
Cl2	0.0259 (2)	0.0242 (2)	0.0381 (3)	−0.00793 (18)	0.0008 (2)	−0.00288 (19)
Cl3	0.0229 (2)	0.0237 (2)	0.0293 (2)	0.00188 (18)	−0.00075 (19)	−0.00623 (17)
Cl4	0.0243 (2)	0.0212 (2)	0.0346 (3)	−0.00105 (17)	−0.0002 (2)	0.00392 (19)
Cl5	0.0211 (2)	0.0293 (2)	0.0231 (2)	0.00007 (18)	−0.00004 (18)	−0.00205 (17)
N1	0.0376 (11)	0.0297 (10)	0.0273 (10)	−0.0036 (9)	0.0048 (9)	0.0014 (8)
C1	0.0298 (10)	0.0194 (9)	0.0241 (10)	−0.0036 (7)	0.0017 (8)	−0.0018 (7)
C2	0.0259 (10)	0.0363 (11)	0.0311 (11)	0.0036 (9)	−0.0029 (8)	0.0026 (9)
C3	0.0289 (11)	0.0432 (12)	0.0361 (12)	0.0019 (9)	0.0072 (9)	0.0010 (10)
C4	0.0423 (13)	0.0242 (10)	0.0281 (11)	−0.0018 (9)	0.0022 (9)	0.0001 (8)
C5	0.0344 (12)	0.0283 (11)	0.0352 (12)	0.0038 (9)	−0.0062 (9)	0.0046 (9)
C6	0.0257 (10)	0.0274 (10)	0.0380 (12)	0.0034 (8)	0.0040 (9)	0.0022 (9)
C7	0.0652 (17)	0.0510 (14)	0.0324 (13)	0.0030 (12)	0.0088 (12)	0.0075 (11)
N2	0.0383 (11)	0.0352 (11)	0.0303 (10)	−0.0064 (9)	0.0065 (9)	0.0023 (8)
C8	0.0297 (11)	0.0280 (10)	0.0292 (10)	−0.0063 (8)	0.0047 (8)	0.0023 (8)
C9	0.0423 (12)	0.0307 (11)	0.0394 (12)	0.0068 (10)	0.0016 (11)	0.0003 (9)
C10	0.0557 (15)	0.0316 (11)	0.0377 (13)	0.0018 (11)	0.0052 (11)	−0.0071 (9)
C11	0.0453 (13)	0.0280 (10)	0.0377 (12)	−0.0103 (10)	−0.0019 (10)	0.0027 (9)
C12	0.0350 (13)	0.0466 (14)	0.0511 (15)	0.0062 (10)	−0.0015 (11)	0.0019 (11)
C13	0.0374 (13)	0.0451 (13)	0.0414 (13)	0.0070 (11)	0.0061 (10)	−0.0069 (10)
C14	0.0718 (19)	0.0462 (13)	0.0447 (15)	−0.0153 (13)	−0.0137 (13)	0.0041 (12)

Geometric parameters (Å, º) top

Cd1—Cd2	3.4082 (2)	C5—C6	1.379 (3)
Cd1—Cl1	2.5051 (5)	C5—H5	0.9500
Cd1—Cl2	2.6560 (5)	C6—H6	0.9500
Cd1—Cl2ⁱ	2.6329 (5)	C7—H7A	0.9800
Cd1—Cl3	2.6462 (5)	C7—H7B	0.9800
Cd1—Cl4	2.7220 (5)	C7—H7C	0.9800
Cd1—Cl5	2.6511 (5)	N2—C8	1.471 (3)
Cd2—Cl3	2.6750 (4)	N2—H2AN	0.87 (3)
Cd2—Cl3ⁱⁱ	2.6750 (4)	N2—H2BN	0.85 (3)
Cd2—Cl4	2.6551 (4)	N2—H2CN	0.93 (4)
Cd2—Cl4ⁱⁱ	2.6551 (4)	C8—C13	1.366 (3)
Cd2—Cl5	2.5764 (5)	C8—C9	1.372 (3)
Cd2—Cl5ⁱⁱ	2.5764 (5)	C9—C10	1.384 (3)
N1—C1	1.468 (3)	C9—H9	0.9500
N1—H1AN	0.86 (3)	C10—C11	1.380 (3)
N1—H1BN	0.90 (4)	C10—H10	0.9500
N1—H1CN	0.80 (3)	C11—C12	1.381 (3)
C1—C2	1.368 (3)	C11—C14	1.511 (3)
C1—C6	1.370 (3)	C12—C13	1.383 (3)
C2—C3	1.383 (3)	C12—H12	0.9500
C2—H2	0.9500	C13—H13	0.9500
C3—C4	1.387 (3)	C14—H14A	0.9800
C3—H3	0.9500	C14—H14B	0.9800
C4—C5	1.380 (3)	C14—H14C	0.9800
C4—C7	1.507 (3)

Cl1—Cd1—Cl2ⁱ	89.894 (17)	H1AN—N1—H1CN	107 (3)
Cl1—Cd1—Cl3	93.735 (16)	H1BN—N1—H1CN	109 (3)
Cl2ⁱ—Cd1—Cl3	174.692 (15)	C2—C1—C6	122.10 (18)
Cl1—Cd1—Cl5	174.745 (17)	C2—C1—N1	118.77 (18)
Cl2ⁱ—Cd1—Cl5	94.211 (15)	C6—C1—N1	119.14 (18)
Cl3—Cd1—Cl5	81.953 (15)	C1—C2—C3	118.58 (19)
Cl1—Cd1—Cl2	97.945 (17)	C1—C2—H2	120.7
Cl2ⁱ—Cd1—Cl2	88.887 (7)	C3—C2—H2	120.7
Cl3—Cd1—Cl2	94.439 (15)	C2—C3—C4	121.1 (2)
Cl5—Cd1—Cl2	85.430 (15)	C2—C3—H3	119.5
Cl1—Cd1—Cl4	95.911 (16)	C4—C3—H3	119.5
Cl2ⁱ—Cd1—Cl4	91.033 (15)	C5—C4—C3	118.23 (19)
Cl3—Cd1—Cl4	84.747 (15)	C5—C4—C7	120.5 (2)
Cl5—Cd1—Cl4	80.755 (15)	C3—C4—C7	121.3 (2)
Cl2—Cd1—Cl4	166.143 (16)	C6—C5—C4	121.54 (19)
Cl1—Cd1—Cd2	126.427 (13)	C6—C5—H5	119.2
Cl2ⁱ—Cd1—Cd2	124.153 (12)	C4—C5—H5	119.2
Cl3—Cd1—Cd2	50.545 (10)	C1—C6—C5	118.45 (19)
Cl5—Cd1—Cd2	48.363 (10)	C1—C6—H6	120.8
Cl2—Cd1—Cd2	120.049 (12)	C5—C6—H6	120.8
Cl4—Cd1—Cd2	49.802 (10)	C4—C7—H7A	109.5
Cl5ⁱⁱ—Cd2—Cl5	180.0	C4—C7—H7B	109.5
Cl5ⁱⁱ—Cd2—Cl4	96.582 (14)	H7A—C7—H7B	109.5
Cl5—Cd2—Cl4	83.419 (14)	C4—C7—H7C	109.5
Cl5ⁱⁱ—Cd2—Cl4ⁱⁱ	83.418 (14)	H7A—C7—H7C	109.5
Cl5—Cd2—Cl4ⁱⁱ	96.580 (14)	H7B—C7—H7C	109.5
Cl4—Cd2—Cl4ⁱⁱ	180.0	C8—N2—H2AN	110.7 (19)
Cl5ⁱⁱ—Cd2—Cl3ⁱⁱ	82.800 (14)	C8—N2—H2BN	108.1 (19)
Cl5—Cd2—Cl3ⁱⁱ	97.198 (14)	H2AN—N2—H2BN	111 (3)
Cl4—Cd2—Cl3ⁱⁱ	94.491 (14)	C8—N2—H2CN	114 (2)
Cl4ⁱⁱ—Cd2—Cl3ⁱⁱ	85.509 (14)	H2AN—N2—H2CN	108 (3)
Cl5ⁱⁱ—Cd2—Cl3	97.198 (14)	H2BN—N2—H2CN	105 (3)
Cl5—Cd2—Cl3	82.804 (14)	C13—C8—C9	121.1 (2)
Cl4—Cd2—Cl3	85.508 (14)	C13—C8—N2	119.6 (2)
Cl4ⁱⁱ—Cd2—Cl3	94.492 (14)	C9—C8—N2	119.2 (2)
Cl3ⁱⁱ—Cd2—Cl3	180.0	C8—C9—C10	118.7 (2)
Cl5ⁱⁱ—Cd2—Cd1	129.733 (10)	C8—C9—H9	120.6
Cl5—Cd2—Cd1	50.270 (10)	C10—C9—H9	120.6
Cl4—Cd2—Cd1	51.542 (10)	C11—C10—C9	121.8 (2)
Cl4ⁱⁱ—Cd2—Cd1	128.458 (10)	C11—C10—H10	119.1
Cl3ⁱⁱ—Cd2—Cd1	130.200 (10)	C9—C10—H10	119.1
Cl3—Cd2—Cd1	49.800 (10)	C10—C11—C12	117.6 (2)
Cl5ⁱⁱ—Cd2—Cd1ⁱⁱ	50.268 (10)	C10—C11—C14	120.8 (2)
Cl5—Cd2—Cd1ⁱⁱ	129.730 (10)	C12—C11—C14	121.6 (2)
Cl4—Cd2—Cd1ⁱⁱ	128.458 (10)	C11—C12—C13	121.5 (2)
Cl4ⁱⁱ—Cd2—Cd1ⁱⁱ	51.542 (10)	C11—C12—H12	119.2
Cl3ⁱⁱ—Cd2—Cd1ⁱⁱ	49.799 (10)	C13—C12—H12	119.2
Cl3—Cd2—Cd1ⁱⁱ	130.200 (10)	C8—C13—C12	119.1 (2)
Cd1—Cd2—Cd1ⁱⁱ	180.0	C8—C13—H13	120.4
Cd1ⁱⁱⁱ—Cl2—Cd1	153.18 (2)	C12—C13—H13	120.4
Cd1—Cl3—Cd2	79.655 (12)	C11—C14—H14A	109.5
Cd2—Cl4—Cd1	78.656 (12)	C11—C14—H14B	109.5
Cd2—Cl5—Cd1	81.367 (13)	H14A—C14—H14B	109.5
C1—N1—H1AN	111.0 (18)	C11—C14—H14C	109.5
C1—N1—H1BN	109 (2)	H14A—C14—H14C	109.5
H1AN—N1—H1BN	109 (3)	H14B—C14—H14C	109.5
C1—N1—H1CN	112 (2)

C6—C1—C2—C3	0.1 (3)	C13—C8—C9—C10	2.6 (3)
N1—C1—C2—C3	−179.64 (19)	N2—C8—C9—C10	−176.2 (2)
C1—C2—C3—C4	0.3 (3)	C8—C9—C10—C11	−1.1 (3)
C2—C3—C4—C5	0.0 (3)	C9—C10—C11—C12	−1.2 (3)
C2—C3—C4—C7	179.1 (2)	C9—C10—C11—C14	177.6 (2)
C3—C4—C5—C6	−0.6 (3)	C10—C11—C12—C13	2.1 (3)
C7—C4—C5—C6	−179.7 (2)	C14—C11—C12—C13	−176.7 (2)
C2—C1—C6—C5	−0.7 (3)	C9—C8—C13—C12	−1.7 (3)
N1—C1—C6—C5	179.06 (18)	N2—C8—C13—C12	177.0 (2)
C4—C5—C6—C1	0.9 (3)	C11—C12—C13—C8	−0.7 (4)

Symmetry codes: (i) −x+3/2, y−1/2, z; (ii) −x+1, −y+2, −z; (iii) −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
N1—H1AN···Cl5ⁱⁱ	0.86 (3)	2.42 (3)	3.258 (2)	166 (2)
N1—H1BN···Cl2^iv	0.91 (3)	2.38 (3)	3.236 (2)	158 (3)
N1—H1CN···Cl4^v	0.80 (3)	2.70 (3)	3.360 (2)	141 (3)
N2—H2AN···Cl3^vi	0.87 (3)	2.34 (3)	3.198 (2)	170 (3)
N2—H2BN···Cl1^vii	0.85 (3)	2.48 (3)	3.273 (2)	156 (2)
N2—H2CN···Cl1^viii	0.93 (4)	2.29 (4)	3.194 (2)	164 (3)

Symmetry codes: (ii) −x+1, −y+2, −z; (iv) x−1/2, −y+3/2, −z; (v) −x+1, −y+1, −z; (vi) x−1/2, y−1, −z+1/2; (vii) x−1/2, y, −z+1/2; (viii) −x+1, y−1/2, −z+1/2.

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Assignment of FT–IR and FT–Raman vibrational frequencies (cm^-1) for I and p-methylanaline

	FT–IR		FT–Raman
Assignment of vibrational frequencies	I	p-methylanaline^a	I	p-methylanaline^b
ν (NH) asymmetric	3510	3416	-	3418
γ NH₂ (twisting)	637	-	638	-
β NH₂ (scis.)	1616	1621	1608	1617
β CH₃ sym	1391	-	1380	1380
γ CH₃ sym	2881	2912	2922	2917
ν (C═C) aromatic	1560, 1503, 1291	1582, 1514, 1441	-	1581, 1281
β (C—H) 1,4-disubstituted	1190, 1114	1176, 1120	1196	1179
ν (C—N)	1243	1267	-	1271
ν (N—H···Cl) intermolecular	3129	-	3126	-

Notes: (a) Haigh et al. (1967);(b) Altun et al. (2003).

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A comparison of selected geometrical parameters (Å) for I, EGUFUI^a, IPEMAS01^b and QOHGUR^c

Distances	I	EGUFUI^a	IPEMAS01^b	QOHGUR^c
Cd1—Cl1	2.5051 (5)	2.4962 (9)	2.4880 (7)	2.496 (2)
Cd1—Cl(2,3,4,5)	2.6329 (5)–2.7220 (5)	2.5882 (9)–2.8926 (9)	2.6218 (7)–2.7404 (6)	2.660 (2)–2.763 (2)
Cd2^d—Cl(3,4,5)	2.5764 (5)–2.6750 (4)	2.5632 (9)–2.7391 (9)	2.5795 (6)–2.6903 (6)	2.577 (2)–2.697 (2)
Cd1···Cd2^d	3.4082 (2)	3.4714 (6)	3.4493 (3)	3.4396 (9)

Notes: (a) Costin-Hogan et al. (2008); (b) Gagor et al. (2011); (c) Liao et al. (2014); (d) Atom Cd2 is located on an inversion centre

Acknowledgements

The authors thank the Central Instrumentation Facility, Pondicherry University, and the Advanced Instrumentation Research Facility, Jawaharlal Nehru University, New Delhi, for access to their analytical facilities. HSE is grateful to the University of Neuchâtel for their support over the years.

Funding information

AS thanks the University Grants Commission, New Delhi, for the award of a UGC Meritorious Fellowship [File No. 4-1/2008 (BSR)].

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