Hydrogen-bonding versus π–π stacking inter­actions in dipyrido[f,h]quinoxaline-6,7-dicarbonitrile and 6,7-di­cyano­dipyrido[f,h]quinoxalin-1-ium chloride dihydrate

The solvent-free title compound, C₁₆H₆N₆, is an aromatic derivative of phenanthroline with an extended π system. It exhibits a remarkable π–π columnar stacking in the crystal structure, with inter­planar distances of 3.229 (3) and 3.380 (3) Å, the shorter spacing being between the two mol­ecules within the asymmetric unit. Adjacent units along the stacked arrays are rotated in-plane with respect to one another by approximately 120°. The hydro­chloride derivative, C₁₆H₇N₆⁺·Cl⁻·2H₂O, in which one of the phenanthroline N atoms has been protonated, crystallized as a dihydrate. The supra­molecular organization in this compound is characterized by continuous hydrogen bonding between the component species, yielding two-dimensional hydrogen-bonded networks. This study demonstrates the high significance of the π–π stacking inter­actions in the solvent-free aromatic system and how they can be undermined by introducing hydrogen-bonding capacity into the ligand.

S1. Comment

The dipyrido[f,h]quinoxaline-6,7-dicarbonitrile ligand (DICNQ) is an attractive building block for the formation of complexes with diverse metal ions. It has several pyridyl and cyano coordination sites for potential coordination of the latter. Moreover, it has an extended π-electron system which may engage in effective π–π stacking interactions to direct the supramolecular organization of the molecular entities. The synthesis and chemical reactivity of various transition metal complexes with DICNQ have been reported (Kozlov & Goldberg, 2008; Stephenson & Hardie, 2006; Xu et al., 2002; Liu et al., 2001; Kulkarni et al., 2004)). Attempts to employ DICNQ in the fabrication of sensing devices have also been described (Arounaguiri & Maiya, 1999; Ambroise & Maiya, 2000; van der Tol et al., 1998). However, the structure of this important ligand has not been characterized before in its uncomplexed form; such a structure determination could provide information about the dominant π–π stacking interactions that characterize the preferred self-organization features inherent to this compound. Only recently were we able to describe the remarkable π–π stacking that dominates the crystal structure of the ethanol solvate of DICNQ (Kozlov, Rubin-Preminger & Goldberg, 2008). During our attempts to synthesize new metal–organic frameworks (rather than discrete complexes) of this ligand, we have now obtained (as a by-product) for the first time X-ray quality crystals of the solvent-free ligand (I). In an additional experiment, the hydrochloride derivative of DICNQ crystallized as a dihydrate, (II). Correspondingly, we report in this paper on the structures of (I) and (II), with an emphasis on the supramolecular self-organization observed in the crystals of the two compounds. In most of the previously published structures, the coordination preference of foreign metal ions dominates the topology of the metal complexes and, in part, the intermolecular organization.

ORTEPIII (Burnett & Johnson, 1996) representations of (I) and (II) are shown in Fig. 1. The asymmetric unit in (I) consists of two crystallographically independent molecules (N1—N22 and N23—N44). The two phenahthroline fragments therein, N1/C2–C11/N12/C13/C14 and N23/C24–C33/N34/C35/C36, are essentially planar. These two planes are nearly parallel to one another, with a dihedral angle between them of 2.48 (6)°. A significant bending of the cyano groups from the respective planes of the phenathroline residues has been observed, with atom N21 deviating 0.345 (6) Å from the N1–C14 plane and atom N44 deviating 0.374 (6) Å from the N23–C36 plane.

As already observed in the crystal structure of the ethanol solvate of DICNQ (Kozlov, Rubin-Preminger & Goldberg, 2008), the intermolecular assembly of these ligand species is dominated by π–π stacking of overlapping phenathroline fragments of adjacent molecules (Fig. 2). Thus, the crystal structure of (I) can be best described as composed of columns of tightly stacked DICNQ ligands. The interplanar distance between the phenanthroline rings in the two molecules of the asymmetric unit is 3.229 (3) Å. This is a remarkably short distance between uncharged overlapping aromatic fragments, which may explain the outward deviations of the cyano groups from the respective phenanthroline plane in order to minimize repulsion between the electron-rich N sites of the overlapping entities. The corresponding interplanar distance between such neighboring pairs displaced along the b axis of the crystal is 3.380 (3) Å [e.g. between the N1–C14 plane and the N23–C36 plane at (x, y - 1, z)], also indicative of significant π–π interactions. These observations are consistent with earlier findings in the structure of the ethanol solvate of DICNQ (Kozlov, Rubin-Preminger & Goldberg, 2008). However, in the former case the overlapping ligands are related by inversion to one another with an aniparallel alignment of the –CN dipoles, the attractive electrostatic interaction between them adding a stabilizing contribution of the columnar organization. In the present case, the π–π stacking arrangement of the DICNQ species is preserved, even though the individual units are oriented differently. For example, the angle between the C13—C14 and C35—C36 central bonds of the phananthroline rings is 60.5 (3)°, and the –CN dipoles of neighboring species thus form an angle of about 120° between them rather than the 180° observed in the earlier study. The resulting columnar organization of the DICNQ species in (I) is illustrated in Fig. 3. The centrosymmetric space symmetry of the entire crystal structure dictates an antiparallel arrangement of adjacent columns related by inversion. Therefore, intermolecular dipolar interactions add to the intercolumnar dispersion forces in stabilizing the overall structure. Molecular modeling calculations are currently being carried out in order to characterize the relative stabilization enthalpies of the different intermolecular organizations in (I) and in the ethanol solvate of DICNQ (Kozlov, Rubin-Preminger & Goldberg, 2008).

Protonation of the DICNQ ligand in (II) occurs on one of the phenanthroline N-atom sites (N12), without affecting to a considerable extent the planarity of the molecular framework. A more subtle inspection of the molecular conformation reveals that the protonated ring C8–C11/N12/C14 is bent slightly with respect to the other pyridyl ring, N1/C2–C5/C13, and the remaining aromatic residue, N1/C2–C8/C13/C14/N15/N16/C17/C18. The corresponding dihedral angles between the mean planes of these fragments are 5.86 (9) and 4.35 (8)°, respectively. The intermolecular organization in (II) is dominated by hydrogen-bonding interactions (Table 1), and it is characterized by minimal overlap between neighboring DICNQ species. The hydrogen bonds propagate from the protonated DICNQ unit (N12/H12) to an adjacent water molecule, from there to two neighboring chloride ions, and then again to a water molecule, forming a continuous hydrogen-bonded layer of the different species (Fig. 4). A view of the crystal structure (Fig. 5) shows that these layers are parallel to the bc plane of the crystal and centered around x = 0. The layers are stacked along the a axis with a lipophilic interface between them around x =1 /2.

The above-described observations indicate that the N-atom sites of the phenathroline fragment of DICNQ are reactive not only to coordination of metal ions but also to protonation, as well as hydrogen-bonding interactions. In its ethanol solvate (Kozlov, Rubin-Preminger & Goldberg, 2008), the ethanol was found to hydrogen bond to one of the N atoms. However, owing to the small size of the solvent molecule this had little disrupting effect on the π–π stacking organization of the neutral DICNQ ligand. The high significance of the stacking interactions to the supramolecular organization of DICNQ has been confirmed by ellucidation of the solvent-free compound (I), which is consistent with similar stacking patterns observed in a large number of phenathroline-derived aromatic compounds (e.g. Gupta et al. 2004; Gut et al., 2002; Bergman et al., 2002). On the other hand, this study shows also that the π–π stacking can be disrupted when an extended hydrogen-bonding scheme is introduced into the system by converting the neutral DICNQ to its hydrochloride derivative, as in (II). It appears that the cooperative charge-assisted hydrogen bonding has in this case a more significant enthalpic contribution than the tight π–π stacking interactions, providing in (II) a dominant structure-directing force.

Related literature

For related literature, see: Ambroise & Maiya (2000); Arounaguiri & Maiya (1999); Bergman et al. (2002); Gupta et al. (2004); Gut et al. (2002); Kozlov & Goldberg (2008a, 2008b); Kulkarni et al. (2004); Liu et al. (2001); Stephenson & Hardie (2006); Tol et al. (1998); Xu et al. (2002).

S2. Experimental

The two title compounds were obtained as by-products of our studies of the coordination chemistry of DICNQ with various metal ions. DICNQ was synthesized by previously reported procedures (Arounaguiri & Maiya, 1999; van der Tol et al., 1998), from commercialy available reagents (Aldrich). We attempted the formation of its palladium complex, by reacting DICNQ (8 mg) with dichlorobis(triphenylphosphine)palladium(II) (12 mg) disolved in acetonitrile (4 ml) and dichloromethane (15 ml). After 3 h of reflux, filtration of the resulting solution followed by one week of slow evaporation, solvent-free crystals of DICNQ were obtained as thin yellow plates. Reaction of DICNQ (8 mg) with lanthanum(III) chloride (14 mg) dissolved in methanol (2 ml) and carbon tetrachloride (15 ml) yielded, after 1 h of reflux, filtration of the resulting solution followed by three months of slow evaporation, crystalline brown pyramids suitable for X-ray diffraction analysis.

S3. Refinement

In (II), H atoms bound to C atoms were located in calculated positions and were constrained to ride on their parent atoms, with C—H distances of 0.95 Å and with U_iso(H) values of 1.2U_eq(C). All other H atoms were located from difference Fourier maps [C—H = 0.87–1.03 Å in (I); see Table 1 for other distances], but their atomic positions were not refined. For them also, U_iso(H) was set at 1.2U_eq(C,N,O). Crystals of (I) exhibited high mosaicity and relatively poor diffraction. The diffraction experiment at 110 K was affected also to some extent by the accummulation of ice of the diffracting sample. Correspondingly, the resulting structural model is characterized by relatively high R factors. No better crystals could be found to improve the experimental data, yet all the H atoms could be clearly located in the difference Fourier map, and the molecular structure seems to be rather precise.

Computing details

For both compounds, data collection: COLLECT (Nonius, 1999); cell refinement: DENZO (Otwinowski & Minor, 1997); data reduction: DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structures of (a) (I) and (b) (II), showing the atom-labeling scheme. The atom ellipsoids represent displacement parameters at the 50% probability level at ca 110 (2) K. H atoms have been omitted.
	Fig. 2. An illustration of the overlapping mode between the two DICNQ units in the asymmetric unit.
	Fig. 3. The crystal packing of (I), illustrating the columnar organization of the DICNQ molecules, as well as their side packing in the crystal structure. H atoms have been omitted.
	Fig. 4. A perpective view of the continuous hydroden-bonding scheme in (II). The hydrogen bonds are denoted by dashed lines. H atoms have been omitted. The chloride ions and the water molecules are indicated by small spheres, the former being crossed. See Table 1 for geometric details.
	Fig. 5. The crystal packing in (II). The polar, charged and hydrophilic entities, inter-connected into hydrogen-bonded layers, are centered at x = 0 and x = 1. A lipophilic surface centered around x = 1/2 characterizes the interface between neighboring layers. H atoms have been omitted. The chloride ions and the water molecules are indicated by small spheres, the former being crossed.

(I) dipyrido[f,h]quinoxaline-6,7-dicarbonitrile

Crystal data

C16H6N6	F(000) = 1152
Mr = 282.27	Dx = 1.509 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 15.0150 (14) Å	Cell parameters from 4063 reflections
b = 6.9620 (6) Å	θ = 1.4–25.0°
c = 24.5189 (16) Å	µ = 0.10 mm^−1
β = 104.224 (5)°	T = 110 K
V = 2484.5 (4) Å^3	Plate, yellow
Z = 8	0.35 × 0.30 × 0.15 mm

Data collection

Nonius KappaCCD diffractometer	2660 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.084
Graphite monochromator	θmax = 25.1°, θmin = 2.5°
Detector resolution: 12.8 pixels mm^-1	h = 0→17
0.5° ϕ and ω scans	k = 0→8
13248 measured reflections	l = −28→28
4340 independent reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.081	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.169	H-atom parameters constrained
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0555P)^2 + 2.1196P] where P = (Fo^2 + 2Fc^2)/3
4340 reflections	(Δ/σ)max < 0.001
397 parameters	Δρmax = 0.23 e Å^−3
0 restraints	Δρmin = −0.26 e Å^−3

Special details

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

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

The analysed crystals were characterized by high mosaic spread, and diffracted poorly.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
N1	0.0704 (2)	0.3133 (4)	0.90121 (12)	0.0281 (8)
C2	−0.0058 (3)	0.3659 (6)	0.86480 (16)	0.0327 (10)
H2	−0.0549	0.3616	0.8778	0.039*
C3	−0.0131 (3)	0.4103 (6)	0.80852 (15)	0.0304 (9)
H3	−0.0692	0.4445	0.7842	0.036*
C4	0.0640 (3)	0.4067 (5)	0.78856 (14)	0.0274 (9)
H4	0.0646	0.4398	0.7500	0.033*
C5	0.1471 (2)	0.3549 (5)	0.82584 (14)	0.0234 (8)
C6	0.2329 (3)	0.3534 (5)	0.80877 (14)	0.0232 (8)
C7	0.3145 (3)	0.2934 (5)	0.84672 (14)	0.0235 (8)
C8	0.3135 (3)	0.2385 (5)	0.90403 (14)	0.0242 (8)
C9	0.3937 (2)	0.1856 (5)	0.94300 (15)	0.0261 (9)
H9	0.4506	0.1832	0.9339	0.031*
C10	0.3895 (3)	0.1321 (5)	0.99600 (14)	0.0284 (9)
H10	0.4402	0.1005	1.0272	0.034*
C11	0.3050 (3)	0.1349 (5)	1.00939 (14)	0.0278 (9)
H11	0.2967	0.0897	1.0477	0.033*
N12	0.2269 (2)	0.1906 (4)	0.97371 (12)	0.0264 (7)
C13	0.1466 (2)	0.3066 (5)	0.88159 (14)	0.0228 (8)
C14	0.2316 (3)	0.2440 (5)	0.92132 (14)	0.0231 (8)
N15	0.2336 (2)	0.4147 (4)	0.75640 (11)	0.0251 (7)
N16	0.3943 (2)	0.2860 (4)	0.83197 (11)	0.0254 (7)
C17	0.3143 (2)	0.4131 (5)	0.74325 (14)	0.0244 (9)
C18	0.3939 (3)	0.3461 (5)	0.78013 (14)	0.0261 (9)
C19	0.3155 (2)	0.4829 (6)	0.68767 (16)	0.0288 (9)
C20	0.4795 (3)	0.3412 (6)	0.76417 (15)	0.0304 (9)
N21	0.3166 (2)	0.5375 (5)	0.64347 (13)	0.0364 (9)
N22	0.5485 (2)	0.3376 (5)	0.75168 (13)	0.0389 (9)
N23	0.0074 (2)	0.8831 (5)	0.86044 (12)	0.0283 (8)
C24	−0.0694 (3)	0.8925 (6)	0.87792 (15)	0.0303 (9)
H24	−0.1210	0.9365	0.8497	0.036*
C25	−0.0774 (3)	0.8423 (5)	0.93150 (15)	0.0294 (9)
H25	−0.1401	0.8495	0.9408	0.035*
C26	−0.0014 (3)	0.7767 (5)	0.96994 (14)	0.0264 (9)
H26	−0.0013	0.7417	1.0067	0.032*
C27	0.0816 (2)	0.7650 (5)	0.95366 (14)	0.0232 (8)
C28	0.1649 (2)	0.6970 (5)	0.99143 (13)	0.0212 (8)
C29	0.2466 (2)	0.6860 (5)	0.97329 (14)	0.0218 (8)
C30	0.2489 (2)	0.7451 (5)	0.91662 (13)	0.0207 (8)
C31	0.3292 (3)	0.7380 (5)	0.89772 (14)	0.0262 (9)
H31	0.3833	0.6887	0.9224	0.031*
C32	0.3272 (3)	0.7940 (5)	0.84388 (15)	0.0273 (9)
H32	0.3808	0.7998	0.8261	0.033*
C33	0.2436 (3)	0.8566 (5)	0.81006 (14)	0.0277 (9)
H33	0.2430	0.8986	0.7728	0.033*
N34	0.1661 (2)	0.8665 (4)	0.82605 (11)	0.0264 (7)
C35	0.0830 (3)	0.8212 (5)	0.89824 (14)	0.0255 (9)
C36	0.1686 (3)	0.8107 (5)	0.87972 (14)	0.0242 (9)
N37	0.1618 (2)	0.6414 (4)	1.04390 (11)	0.0249 (7)
N38	0.3246 (2)	0.6204 (4)	1.00712 (11)	0.0234 (7)
C39	0.2392 (2)	0.5753 (5)	1.07664 (14)	0.0234 (8)
C40	0.3194 (2)	0.5643 (5)	1.05802 (14)	0.0232 (8)
C41	0.2379 (2)	0.5126 (5)	1.13276 (15)	0.0262 (9)
C42	0.4015 (3)	0.4789 (6)	1.09385 (14)	0.0266 (9)
N43	0.2383 (2)	0.4598 (5)	1.17721 (13)	0.0321 (8)
N44	0.4638 (2)	0.4043 (5)	1.12187 (13)	0.0350 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0252 (19)	0.0304 (19)	0.0280 (17)	0.0016 (14)	0.0050 (15)	0.0012 (14)
C2	0.027 (2)	0.036 (2)	0.036 (2)	−0.0012 (18)	0.0094 (19)	−0.0017 (19)
C3	0.026 (2)	0.033 (2)	0.030 (2)	0.0007 (18)	0.0016 (17)	0.0014 (18)
C4	0.030 (2)	0.028 (2)	0.0224 (19)	−0.0017 (17)	0.0020 (17)	−0.0005 (16)
C5	0.024 (2)	0.020 (2)	0.0268 (19)	−0.0026 (16)	0.0077 (16)	−0.0023 (16)
C6	0.033 (2)	0.018 (2)	0.0193 (18)	−0.0039 (16)	0.0066 (16)	−0.0042 (15)
C7	0.027 (2)	0.020 (2)	0.0226 (19)	−0.0028 (16)	0.0044 (17)	−0.0055 (16)
C8	0.031 (2)	0.019 (2)	0.0227 (19)	−0.0033 (16)	0.0060 (17)	−0.0020 (16)
C9	0.024 (2)	0.024 (2)	0.029 (2)	0.0012 (16)	0.0040 (17)	−0.0004 (17)
C10	0.033 (2)	0.027 (2)	0.0218 (19)	0.0039 (17)	0.0005 (17)	0.0017 (17)
C11	0.035 (2)	0.023 (2)	0.0224 (19)	0.0004 (17)	0.0018 (17)	−0.0005 (16)
N12	0.0288 (19)	0.0250 (18)	0.0253 (17)	−0.0036 (14)	0.0067 (14)	−0.0032 (14)
C13	0.025 (2)	0.018 (2)	0.0241 (19)	−0.0017 (16)	0.0038 (16)	−0.0032 (16)
C14	0.033 (2)	0.0163 (19)	0.0204 (19)	−0.0040 (16)	0.0061 (17)	−0.0024 (15)
N15	0.0265 (18)	0.0270 (18)	0.0204 (16)	−0.0027 (14)	0.0033 (13)	−0.0008 (14)
N16	0.0276 (19)	0.0270 (18)	0.0212 (16)	0.0009 (14)	0.0051 (14)	−0.0007 (14)
C17	0.028 (2)	0.025 (2)	0.0202 (18)	−0.0021 (17)	0.0056 (16)	−0.0023 (16)
C18	0.029 (2)	0.027 (2)	0.024 (2)	−0.0019 (17)	0.0084 (17)	−0.0031 (17)
C19	0.024 (2)	0.036 (2)	0.025 (2)	−0.0010 (17)	0.0032 (17)	−0.0047 (19)
C20	0.029 (2)	0.038 (2)	0.023 (2)	0.0020 (18)	0.0039 (18)	0.0002 (18)
N21	0.039 (2)	0.041 (2)	0.0283 (19)	0.0000 (17)	0.0065 (16)	0.0016 (17)
N22	0.033 (2)	0.052 (2)	0.0313 (19)	0.0024 (17)	0.0085 (16)	0.0018 (17)
N23	0.0220 (18)	0.0324 (19)	0.0271 (17)	−0.0011 (14)	−0.0002 (14)	−0.0019 (14)
C24	0.024 (2)	0.032 (2)	0.030 (2)	0.0019 (17)	−0.0025 (17)	0.0033 (18)
C25	0.024 (2)	0.032 (2)	0.032 (2)	0.0008 (17)	0.0067 (17)	−0.0021 (18)
C26	0.027 (2)	0.028 (2)	0.025 (2)	−0.0008 (17)	0.0074 (17)	−0.0042 (17)
C27	0.027 (2)	0.018 (2)	0.0225 (18)	0.0004 (16)	0.0024 (16)	−0.0026 (16)
C28	0.026 (2)	0.018 (2)	0.0188 (18)	−0.0016 (16)	0.0041 (16)	−0.0016 (15)
C29	0.024 (2)	0.020 (2)	0.0198 (18)	−0.0024 (16)	0.0032 (16)	−0.0015 (15)
C30	0.024 (2)	0.020 (2)	0.0176 (18)	−0.0017 (15)	0.0040 (15)	−0.0020 (15)
C31	0.027 (2)	0.026 (2)	0.026 (2)	−0.0010 (17)	0.0069 (17)	−0.0003 (17)
C32	0.035 (2)	0.022 (2)	0.028 (2)	−0.0006 (17)	0.0134 (18)	−0.0042 (17)
C33	0.040 (3)	0.024 (2)	0.0205 (19)	−0.0014 (17)	0.0090 (18)	−0.0015 (16)
N34	0.0337 (19)	0.0260 (18)	0.0193 (16)	0.0001 (14)	0.0059 (14)	−0.0006 (14)
C35	0.030 (2)	0.020 (2)	0.0232 (19)	−0.0006 (16)	0.0017 (17)	−0.0031 (16)
C36	0.031 (2)	0.017 (2)	0.0230 (19)	−0.0033 (16)	0.0038 (17)	−0.0027 (16)
N37	0.0267 (18)	0.0250 (18)	0.0228 (16)	−0.0019 (14)	0.0060 (14)	−0.0011 (14)
N38	0.0250 (18)	0.0255 (18)	0.0184 (15)	−0.0007 (14)	0.0028 (13)	−0.0018 (13)
C39	0.024 (2)	0.025 (2)	0.0186 (18)	0.0008 (16)	0.0000 (16)	0.0003 (16)
C40	0.024 (2)	0.022 (2)	0.0226 (19)	0.0005 (16)	0.0031 (16)	−0.0025 (16)
C41	0.022 (2)	0.031 (2)	0.024 (2)	0.0016 (17)	0.0021 (16)	−0.0003 (18)
C42	0.028 (2)	0.032 (2)	0.0206 (19)	−0.0028 (18)	0.0076 (17)	−0.0025 (17)
N43	0.033 (2)	0.037 (2)	0.0253 (18)	0.0037 (15)	0.0055 (15)	0.0006 (16)
N44	0.029 (2)	0.044 (2)	0.0282 (17)	0.0007 (17)	0.0008 (15)	0.0021 (16)

Geometric parameters (Å, º)

N1—C2	1.319 (5)	N23—C24	1.326 (5)
N1—C13	1.346 (4)	N23—C35	1.348 (4)
C2—C3	1.392 (5)	C24—C25	1.393 (5)
C2—H2	0.8722	C24—H24	0.9542
C3—C4	1.363 (5)	C25—C26	1.368 (5)
C3—H3	0.9353	C25—H25	1.0225
C4—C5	1.401 (5)	C26—C27	1.400 (5)
C4—H4	0.9757	C26—H26	0.9324
C5—C13	1.410 (5)	C27—C35	1.419 (5)
C5—C6	1.449 (5)	C27—C28	1.441 (5)
C6—N15	1.356 (4)	C28—N37	1.355 (4)
C6—C7	1.408 (5)	C28—C29	1.407 (5)
C7—N16	1.335 (5)	C29—N38	1.338 (4)
C7—C8	1.460 (5)	C29—C30	1.458 (5)
C8—C9	1.390 (5)	C30—C36	1.395 (5)
C8—C14	1.396 (5)	C30—C31	1.395 (5)
C9—C10	1.368 (5)	C31—C32	1.370 (5)
C9—H9	0.9355	C31—H31	0.9499
C10—C11	1.387 (5)	C32—C33	1.393 (5)
C10—H10	0.9631	C32—H32	1.0065
C11—N12	1.336 (5)	C33—N34	1.318 (5)
C11—H11	1.0274	C33—H33	0.9583
N12—C14	1.356 (4)	N34—C36	1.364 (4)
C13—C14	1.469 (5)	C35—C36	1.466 (5)
N15—C17	1.328 (4)	N37—C39	1.323 (4)
N16—C18	1.337 (4)	N38—C40	1.328 (4)
C17—C18	1.391 (5)	C39—C40	1.391 (5)
C17—C19	1.451 (5)	C39—C41	1.448 (5)
C18—C20	1.433 (6)	C40—C42	1.453 (5)
C19—N21	1.152 (4)	C41—N43	1.149 (4)
C20—N22	1.151 (5)	C42—N44	1.141 (4)
C2—N1—C13	116.1 (3)	C24—N23—C35	116.5 (3)
N1—C2—C3	125.2 (4)	N23—C24—C25	125.2 (3)
N1—C2—H2	114.5	N23—C24—H24	113.4
C3—C2—H2	120.1	C25—C24—H24	121.4
C4—C3—C2	119.1 (3)	C26—C25—C24	118.8 (4)
C4—C3—H3	119.1	C26—C25—H25	121.4
C2—C3—H3	121.8	C24—C25—H25	119.7
C3—C4—C5	118.0 (3)	C25—C26—C27	118.2 (3)
C3—C4—H4	123.7	C25—C26—H26	123.7
C5—C4—H4	118.3	C27—C26—H26	118.0
C4—C5—C13	118.6 (3)	C26—C27—C35	118.7 (3)
C4—C5—C6	121.7 (3)	C26—C27—C28	121.9 (3)
C13—C5—C6	119.7 (3)	C35—C27—C28	119.4 (3)
N15—C6—C7	120.7 (3)	N37—C28—C29	121.4 (3)
N15—C6—C5	119.1 (3)	N37—C28—C27	118.5 (3)
C7—C6—C5	120.2 (3)	C29—C28—C27	120.1 (3)
N16—C7—C6	121.8 (3)	N38—C29—C28	121.4 (3)
N16—C7—C8	118.2 (3)	N38—C29—C30	117.7 (3)
C6—C7—C8	120.0 (3)	C28—C29—C30	120.8 (3)
C9—C8—C14	118.5 (3)	C36—C30—C31	118.5 (3)
C9—C8—C7	121.3 (3)	C36—C30—C29	119.5 (3)
C14—C8—C7	120.2 (3)	C31—C30—C29	122.1 (3)
C10—C9—C8	119.4 (3)	C32—C31—C30	119.6 (3)
C10—C9—H9	118.6	C32—C31—H31	122.0
C8—C9—H9	121.9	C30—C31—H31	118.4
C9—C10—C11	118.6 (3)	C31—C32—C33	117.8 (4)
C9—C10—H10	127.3	C31—C32—H32	126.8
C11—C10—H10	113.9	C33—C32—H32	115.4
N12—C11—C10	123.7 (3)	N34—C33—C32	124.8 (3)
N12—C11—H11	113.8	N34—C33—H33	117.8
C10—C11—H11	122.4	C32—C33—H33	117.3
C11—N12—C14	117.3 (3)	C33—N34—C36	117.1 (3)
N1—C13—C5	123.1 (3)	N23—C35—C27	122.5 (3)
N1—C13—C14	116.7 (3)	N23—C35—C36	117.2 (3)
C5—C13—C14	120.2 (3)	C27—C35—C36	120.2 (3)
N12—C14—C8	122.3 (3)	N34—C36—C30	122.2 (3)
N12—C14—C13	118.1 (3)	N34—C36—C35	117.8 (3)
C8—C14—C13	119.6 (3)	C30—C36—C35	119.9 (3)
C17—N15—C6	116.6 (3)	C39—N37—C28	116.4 (3)
C7—N16—C18	116.8 (3)	C40—N38—C29	116.0 (3)
N15—C17—C18	122.3 (3)	N37—C39—C40	121.5 (3)
N15—C17—C19	116.7 (3)	N37—C39—C41	117.8 (3)
C18—C17—C19	121.0 (3)	C40—C39—C41	120.7 (3)
N16—C18—C17	121.7 (3)	N38—C40—C39	123.2 (3)
N16—C18—C20	117.2 (3)	N38—C40—C42	116.9 (3)
C17—C18—C20	121.1 (3)	C39—C40—C42	119.8 (3)
N21—C19—C17	179.7 (5)	N43—C41—C39	178.4 (4)
N22—C20—C18	179.6 (4)	N44—C42—C40	177.0 (4)

(II) 6,7-dicyanodipyrido[f,h]quinoxalin-1-ium chloride dihydrate

Crystal data

C16H7N6^+·Cl^−·2H2O	F(000) = 728
Mr = 354.76	Dx = 1.476 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 13.9417 (4) Å	Cell parameters from 3363 reflections
b = 12.0846 (4) Å	θ = 2.3–28.2°
c = 9.6350 (3) Å	µ = 0.26 mm^−1
β = 100.452 (2)°	T = 110 K
V = 1596.37 (9) Å^3	Prism, brown
Z = 4	0.35 × 0.20 × 0.15 mm

Data collection

Nonius KappaCCD diffractometer	2381 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.064
Graphite monochromator	θmax = 26.0°, θmin = 2.3°
Detector resolution: 12.8 pixels mm^-1	h = −17→16
1° ω scans	k = −14→0
10352 measured reflections	l = 0→11
3123 independent reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.052	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.115	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0452P)^2 + 1.1734P] where P = (Fo^2 + 2Fc^2)/3
3123 reflections	(Δ/σ)max < 0.001
226 parameters	Δρmax = 0.32 e Å^−3
0 restraints	Δρmin = −0.32 e Å^−3

Special details

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. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
N1	0.75973 (14)	−0.33233 (16)	0.7918 (2)	0.0221 (4)
C2	0.70713 (17)	−0.40347 (19)	0.7032 (3)	0.0241 (5)
H2	0.7138	−0.4801	0.7246	0.029*
C3	0.64304 (17)	−0.37227 (19)	0.5812 (3)	0.0241 (5)
H3	0.6065	−0.4264	0.5225	0.029*
C4	0.63348 (17)	−0.26156 (19)	0.5468 (3)	0.0227 (5)
H4	0.5907	−0.2380	0.4639	0.027*
C5	0.68847 (16)	−0.18459 (18)	0.6371 (2)	0.0196 (5)
C6	0.68205 (16)	−0.06605 (19)	0.6108 (2)	0.0199 (5)
C7	0.73486 (16)	0.00940 (19)	0.7081 (2)	0.0204 (5)
C8	0.79683 (16)	−0.03143 (19)	0.8362 (2)	0.0208 (5)
C9	0.84669 (16)	0.0393 (2)	0.9396 (2)	0.0232 (5)
H9	0.8428	0.1173	0.9267	0.028*
C10	0.90165 (17)	−0.0048 (2)	1.0605 (3)	0.0258 (5)
H10	0.9342	0.0425	1.1328	0.031*
C11	0.90891 (16)	−0.1190 (2)	1.0755 (2)	0.0244 (5)
H11	0.9474	−0.1501	1.1578	0.029*
N12	0.86187 (13)	−0.18547 (16)	0.9746 (2)	0.0215 (4)
H12	0.8671	−0.2630	0.9916	0.026*
C13	0.74986 (16)	−0.22408 (19)	0.7580 (2)	0.0201 (5)
C14	0.80420 (16)	−0.14550 (19)	0.8562 (2)	0.0203 (5)
N15	0.62308 (14)	−0.03087 (16)	0.4928 (2)	0.0218 (4)
N16	0.72888 (14)	0.11932 (16)	0.6872 (2)	0.0225 (4)
C17	0.61963 (17)	0.0777 (2)	0.4715 (2)	0.0222 (5)
C18	0.67229 (17)	0.15258 (19)	0.5684 (3)	0.0233 (5)
C19	0.55883 (18)	0.1163 (2)	0.3424 (3)	0.0264 (5)
C20	0.66499 (18)	0.2700 (2)	0.5376 (3)	0.0276 (6)
N21	0.51073 (17)	0.1478 (2)	0.2413 (3)	0.0387 (6)
N22	0.65543 (18)	0.36158 (19)	0.5067 (3)	0.0389 (6)
Cl23	0.85399 (4)	−0.61888 (5)	0.89553 (6)	0.02914 (18)
O24	0.91258 (12)	−0.39233 (14)	1.06754 (18)	0.0293 (4)
H24A	0.8906	−0.4428	1.0066	0.035*
H24B	0.9801	−0.3869	1.0743	0.035*
O25	0.95440 (14)	−0.74483 (16)	1.1736 (2)	0.0370 (5)
H25A	0.9169	−0.7620	1.2406	0.044*
H25B	0.9127	−0.7035	1.1041	0.044*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0276 (10)	0.0170 (10)	0.0219 (10)	0.0004 (8)	0.0051 (9)	0.0020 (8)
C2	0.0291 (12)	0.0176 (12)	0.0265 (13)	−0.0023 (10)	0.0076 (11)	−0.0013 (10)
C3	0.0268 (12)	0.0196 (12)	0.0263 (13)	−0.0029 (10)	0.0058 (10)	−0.0033 (10)
C4	0.0238 (12)	0.0234 (13)	0.0208 (12)	0.0011 (10)	0.0036 (10)	−0.0025 (10)
C5	0.0208 (11)	0.0178 (12)	0.0210 (12)	0.0008 (9)	0.0056 (10)	−0.0007 (10)
C6	0.0204 (11)	0.0192 (12)	0.0213 (12)	−0.0005 (9)	0.0070 (10)	−0.0007 (10)
C7	0.0231 (11)	0.0174 (12)	0.0219 (12)	0.0003 (9)	0.0078 (10)	−0.0012 (10)
C8	0.0216 (11)	0.0213 (12)	0.0206 (12)	−0.0021 (9)	0.0071 (10)	−0.0021 (10)
C9	0.0237 (12)	0.0211 (12)	0.0257 (13)	−0.0028 (10)	0.0069 (10)	−0.0043 (10)
C10	0.0258 (12)	0.0286 (14)	0.0229 (12)	−0.0037 (11)	0.0042 (10)	−0.0063 (11)
C11	0.0213 (11)	0.0307 (14)	0.0211 (12)	0.0000 (10)	0.0037 (10)	0.0000 (11)
N12	0.0230 (10)	0.0202 (11)	0.0206 (10)	0.0006 (8)	0.0020 (8)	0.0006 (8)
C13	0.0203 (11)	0.0191 (12)	0.0225 (12)	−0.0009 (9)	0.0083 (10)	0.0001 (10)
C14	0.0208 (11)	0.0208 (12)	0.0199 (11)	0.0006 (9)	0.0059 (10)	−0.0006 (10)
N15	0.0232 (10)	0.0208 (10)	0.0217 (10)	0.0020 (8)	0.0051 (8)	0.0011 (8)
N16	0.0270 (10)	0.0188 (10)	0.0226 (10)	−0.0014 (8)	0.0070 (9)	0.0003 (8)
C17	0.0228 (12)	0.0223 (12)	0.0226 (12)	0.0031 (10)	0.0067 (10)	0.0032 (10)
C18	0.0268 (12)	0.0188 (12)	0.0266 (13)	0.0003 (10)	0.0110 (11)	0.0006 (10)
C19	0.0283 (13)	0.0232 (13)	0.0283 (14)	0.0038 (11)	0.0071 (11)	0.0016 (11)
C20	0.0304 (13)	0.0231 (14)	0.0306 (14)	0.0002 (11)	0.0086 (11)	0.0019 (11)
N21	0.0368 (13)	0.0443 (15)	0.0352 (13)	0.0105 (11)	0.0074 (11)	0.0076 (12)
N22	0.0471 (14)	0.0248 (13)	0.0474 (15)	0.0028 (10)	0.0152 (12)	0.0024 (11)
Cl23	0.0321 (3)	0.0287 (3)	0.0262 (3)	0.0032 (3)	0.0041 (2)	0.0021 (3)
O24	0.0280 (9)	0.0274 (10)	0.0324 (10)	0.0003 (7)	0.0054 (8)	−0.0040 (8)
O25	0.0391 (11)	0.0394 (11)	0.0307 (10)	−0.0021 (9)	0.0018 (9)	0.0077 (8)

Geometric parameters (Å, º)

N1—C2	1.334 (3)	C10—C11	1.390 (4)
N1—C13	1.349 (3)	C10—H10	0.9500
C2—C3	1.394 (3)	C11—N12	1.338 (3)
C2—H2	0.9500	C11—H11	0.9500
C3—C4	1.379 (3)	N12—C14	1.360 (3)
C3—H3	0.9500	N12—H12	0.9515
C4—C5	1.403 (3)	C13—C14	1.453 (3)
C4—H4	0.9500	N15—C17	1.328 (3)
C5—C13	1.398 (3)	N16—C18	1.329 (3)
C5—C6	1.455 (3)	C17—C18	1.408 (3)
C6—N15	1.345 (3)	C17—C19	1.449 (4)
C6—C7	1.415 (3)	C18—C20	1.449 (3)
C7—N16	1.344 (3)	C19—N21	1.143 (3)
C7—C8	1.458 (3)	C20—N22	1.148 (3)
C8—C14	1.393 (3)	O24—H24A	0.8639
C8—C9	1.399 (3)	O24—H24B	0.9335
C9—C10	1.380 (3)	O25—H25A	0.9245
C9—H9	0.9500	O25—H25B	0.9461
C2—N1—C13	116.8 (2)	C9—C10—H10	120.3
N1—C2—C3	124.0 (2)	C11—C10—H10	120.3
N1—C2—H2	118.0	N12—C11—C10	120.2 (2)
C3—C2—H2	118.0	N12—C11—H11	119.9
C4—C3—C2	119.0 (2)	C10—C11—H11	119.9
C4—C3—H3	120.5	C11—N12—C14	122.3 (2)
C2—C3—H3	120.5	C11—N12—H12	116.9
C3—C4—C5	118.4 (2)	C14—N12—H12	120.7
C3—C4—H4	120.8	N1—C13—C5	123.5 (2)
C5—C4—H4	120.8	N1—C13—C14	117.3 (2)
C13—C5—C4	118.3 (2)	C5—C13—C14	119.2 (2)
C13—C5—C6	119.4 (2)	N12—C14—C8	119.0 (2)
C4—C5—C6	122.4 (2)	N12—C14—C13	118.2 (2)
N15—C6—C7	121.4 (2)	C8—C14—C13	122.7 (2)
N15—C6—C5	117.8 (2)	C17—N15—C6	116.3 (2)
C7—C6—C5	120.7 (2)	C18—N16—C7	116.0 (2)
N16—C7—C6	121.8 (2)	N15—C17—C18	122.2 (2)
N16—C7—C8	118.2 (2)	N15—C17—C19	116.8 (2)
C6—C7—C8	120.0 (2)	C18—C17—C19	121.1 (2)
C14—C8—C9	119.5 (2)	N16—C18—C17	122.3 (2)
C14—C8—C7	118.0 (2)	N16—C18—C20	118.8 (2)
C9—C8—C7	122.5 (2)	C17—C18—C20	119.0 (2)
C10—C9—C8	119.6 (2)	N21—C19—C17	179.3 (3)
C10—C9—H9	120.2	N22—C20—C18	176.2 (3)
C8—C9—H9	120.2	H24A—O24—H24B	109.0
C9—C10—C11	119.4 (2)	H25A—O25—H25B	105.1

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N12—H12···O24	0.95	1.79	2.706 (3)	160
O24—H24A···Cl23	0.86	2.39	3.2277 (18)	162
O24—H24B···Cl23^i	0.93	2.28	3.2119 (18)	176
O25—H25A···Cl23^ii	0.92	2.36	3.2140 (19)	154
O25—H25B···Cl23	0.95	2.27	3.177 (2)	160

Symmetry codes: (i) −x+2, −y−1, −z+2; (ii) x, −y−3/2, z+1/2.