Inter­molecular hydrogen bonding in N-methyl-N′-(pyridin-2-yl)benzene-1,2-di­amine

Unexpected dual inter­molecular hydrogen bonding has been observed in a class of N-aryl-substituted ortho-phenyl­ene di­amine compounds. Initially detected in solution by the observation of unexplained signals in the ¹H NMR spectrum, it was further corroborated by two-dimensional COSY NMR spectroscopy and solid-state X-ray crystallography data.

Abstract

The structure of N-methyl-N′-(pyridin-2-yl)benzene-1,2-di­amine, C₁₂H₁₃N₃, at 123 K has ortho­rhom­bic (Pna2₁) symmetry. The title compound displays an unexpected proton-splitting pattern when studied by ¹H NMR spectroscopy. The X-ray crystallography analysis determined this to be caused by strong dual N—H⋯N hydrogen bonding.

1. Chemical context

ortho-Phenyl­ene di­amine compounds are valuable precursors that have widespread use in a number of applications, especially as carbene ligands (Peris, 2018 ▸; Flanigan et al., 2015 ▸; Hopkinson et al., 2014 ▸; Fèvre et al., 2013 ▸; Velazquez & Verpoort, 2012 ▸; Doddi et al., 2019 ▸). The synthesis of ortho-phenyl­ene di­amine derivatives, whether it be introducing functionality on the aryl ring or the nitro­gen atom of the amine group, remains a challenge and continues to attract ongoing efforts to develop efficient synthetic routes to access a diverse library of functionalized compounds. We have been inter­ested in functionalized symmetrical and unsymmetrical ortho-phenyl­ene di­amine derivatives to access organometallic compounds for use in catalysis applications (Wang et al., 2013 ▸) and novel aza­borole systems (Abbey & Liu, 2013 ▸; Weber, 2012 ▸, 2008 ▸; Segawa et al., 2009 ▸). Although a number of symmetrical ligands, such as I and II, are readily available commercially, unsymmetrical ligands, such III and IV, are less common because the chemical routes and purification processes to access these compounds are more complicated (substituted ortho-phenyl­ene di­amine compounds I–VI of inter­est are shown in the scheme below).

Compound IV was synthesized by a modification of a literature procedure (Wang et al., 2013 ▸). Analysis of the compound using ¹H NMR spectroscopy to confirm the purity revealed some unexpected findings (see supporting information) when compared with similar compounds shown in the scheme. Upon initial purification and isolation of IV, analysis by proton NMR in CDCl₃ sometimes showed what seemed to be two different methyl signals, which we initially assumed was a contaminant originating from the reaction that could not be easily removed. However, analysis of the same material by ¹³C NMR spectroscopy showed a relatively simple and clean spectrum, suggesting signals for only a single compound or, if a second compound was present, the signals could be overlapping and therefore difficult to distinguish. Previously reported compounds I and II are both symmetrical and show very simple and expected signals in their respective ¹H NMR spectra (see Figs. S1 and S2). The methyl signal of I was found as a singlet at 2.9 ppm and NH protons as a broad singlet at 3.0–3.5 ppm. Meanwhile, compound II shows the NH protons occurring as a broad singlet further downfield at 5.5–5.7 ppm, presumably caused by deshielding effects of the aryl substit­uents. Analysis of compound IV in CDCl₃ shows well-defined signals that can be attributed to the aryl and pyridyl protons occurring in the downfield region between 6.3–8.3 ppm region (Fig. S3). The methyl signal occurs at 2.85 ppm, and it is inter­esting to see two different types of NH protons, a broad singlet at 4.1–4.5 ppm and a broad multiplet at 6.2–6.3 ppm. While we expect the chemical environments to be significantly different for the NH protons, we were unable to explain the multiplet-nature or coupling of these NH protons to another proton spin system. To further probe these unusual spectroscopic features, proton NMR analysis was undertaken in d ₆-DMSO (Fig. S4), which resulted in significant sharpening of the NH signals. The initial broad NH peak now appears as a broad multiplet around 5 ppm, and the methyl signal is split into a second order doublet, which was very unexpected. 2D COSY spectroscopy in d ₆-DMSO was performed on the same NMR sample (Fig. 1 ▸) and clearly showed the upfield NH multiplet at 5 ppm to be directly coupled through the nitro­gen atom with the neighbouring protons on the methyl group. On the NMR time scale, proton-to-methyl coupling through the nitro­gen atom is never reported as the NH proton is extremely labile (i.e. evident by very broad or even undetectable signals in proton NMR spectra) and readily undergoes facile exchange: to the best of our knowledge this type of NH proton coupling is exceptionally rare. In addition, the other downfield NH proton has sharpened further in d ₆-DMSO and appears as a multiplet at 6.4–6.5ppm, which suggests this NH proton may be involved in longer range coupling of the protons in the pyridyl ring. From the COSY spectrum, it appears that this NH proton is involved in long-range coupling with the pyridyl and/or phenyl protons. To understand the cause of this unexplained coupling observed in the ¹H NMR spectra for compound IV, analysis by X-ray crystallographic methods was undertaken.

Figure 1.

Two-dimensional COSY spectrum of N-methyl-N-phenyl-1,2-di­amino­benzene, IV (d ₆-DMSO).

2. Structural commentary

The mol­ecular structure and atom-numbering scheme of the title compound is shown in Fig. 2 ▸. The asymmetric unit comprises two independent mol­ecules assembled in a self-complementary N—H⋯N hydrogen-bonded dimer with a classical ring motif (Table 1 ▸). The overall configuration of the N′-(2-pyrid­yl)-benzene-1,2-di­amine core of the mol­ecule is very similar to that observed in the closely related compound, N-(2-bromo­benz­yl)-N′-(2-pyrid­yl)-benzene-1,2-di­amine (Man­jare et al., 2009 ▸). The angles between the mean planes of the pyridyl and o-di­amino­phenyl rings are 61.80 (10) and 62.33 (10)° for mol­ecules I and II, respectively. In this configuration, the second N—H moiety on each mol­ecule is sufficiently close to the opposing pyridyl nitro­gen atom, resulting in two further but much weaker N—H⋯N inter­actions (Table 1 ▸). Notably, the equivalent D⋯A distances in N-(2-bromo­benz­yl)-N′-(2-pyrid­yl)-benzene-1,2-di­amine are approximately 0.3 Å longer. The pyridyl-amine C—N bond distances in each mol­ecule of the title compound [C1—N1 = 1.368 (3), C13—-N4 = 1.370 (3) Å] are significantly shorter than the neighbouring phenyl-amine C—N distances [C6—N1 = 1.418 (3), C18—N4 = 1.418 (3) Å], plausibly indicative of some electron delocalization associated within the pyridyl-amine fragment. Similarly, the C—N bonds associated with the second amine group display the same variation with shorter distances to the aryl-amine fragment and longer to the methyl group.

Figure 2.

Mol­ecular diagram of the title compound, with non-hydrogen atoms represented by 50% displacement ellipsoids and hydrogen atoms as spheres of arbitrary size.

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N4—H4⋯N2	0.90 (3)	2.11 (3)	3.001 (3)	173 (2)
N1—H1⋯N5	0.88 (3)	2.11 (3)	2.981 (3)	173 (2)
N6—H6⋯N2	0.88 (3)	2.62 (2)	3.374 (2)	145 (2)
N3—H3⋯N5	0.87 (3)	2.61 (3)	3.337 (2)	142 (2)

Solution and solid-state structural studies of substituted 2-aryl­amino-pyridine derivatives indicate that these mol­ecules can form two different stable conformations through rotation of the aryl ring about the C—N bond (Takasuka et al., 1986 ▸). In one conformation, the pyridyl and aryl rings are not co-planar, whereas in the alternate conformation the two rings are co-planar, with an inter­molecular C—H⋯N inter­action between the pyridyl nitro­gen atoms and the 2-aminoaryl ring. The former leads to dimer formation such as observed for the parent compound 2-(phenyl­amino)­pyridine (Polamo, et al., 1997 ▸) and in the current example. In contrast, the latter conformation may lead to alternate structural motifs such as 1-D catemer chains (Talja & Polamo, 2005 ▸; Polamo & Talja, 2004 ▸) or inter­actions with other functional groups (Takasuka et al., 1986 ▸). The structure of N,N′-bis­(2-pyrid­yl)benzene-1,2-di­amine shows both conformations in a single mol­ecule (Gdaniec et al., 2004 ▸).

Of greater inter­est is compound VI, which is very similar to our current compound IV. While compound VI contains the bulky 2-bromo-benzyl group attached to one amino group, it still forms the hydrogen-bonded dimer V complex. The reported proton NMR spectrum of V in CDCl₃ (Manjare et al., 2009 ▸) reveals some inter­esting features that are similar to those of compound IV. The methyl­ene protons on VI are magnetically non-equivalent whereby each proton has a different chemical shift of 4.83 and 4.41 ppm and are strongly coupled to each other. The two NH protons are also in different environments, one located downfield at 6.15 ppm as a multiplet and the other lies under a methyl­ene proton signal at 4.41 ppm, which are essentially in the same location as for compound IV. Inter­estingly, as compound VI is only analysed in CDCl₃, the authors do not observe any coupling of the NH proton with either of the methyl­ene protons. We suspect the CH₃–NH coupling observed in IV when using CDCl₃ is less pronounced or enhanced by solvation effects than when using d ₆-DMSO. Nevertheless, the presence and observation of this CH₃–NH coupling in compound IV, to the best of our knowledge, is rare, and in this case a result of the dual inter­molecular hydrogen bonding, occurring from the primary amino-pyridine dimer complex and secondary pyridyl and CH₃–NH inter­action.

3. Supra­molecular features

The crystal packing of the title compound involves no π–π ring inter­actions [minimum Cg⋯Cg separation 4.7654 (12) Å, dihedral angle 58.68 (10)°]. There are two minor C—H⋯Cg inter­actions linking the dimers into a supra­molecular two-dimensional sheet lying parallel to the ab plane [Fig. 3 ▸; C12 ⋯Cg4ⁱ = 3.456 (3) Å, C12—H⋯Cg4ⁱ = 150°, H⋯Cg4ⁱ = 2.66 Å, and C24⋯Cg2ⁱⁱ = 3.565 (3) Å, C24—H⋯Cg2ⁱⁱ = 152°, H⋯Cg2ⁱⁱ = 2.67 Å; Cg2 and Cg4 are the centroids of rings C6–C11 and C18–C23, respectively; symmetry codes: (i) x −  ,  − y, z; (ii)  + x,  − y, z].

Figure 3.

A view of the unit-cell packing, showing a single 2-D layer of hydrogen-bonded dimer mol­ecules.

4. Database survey

A search of the Cambridge Structure Database (CSD version 5.43, November 2021; Groom et al., 2016 ▸) for substituted o-di­amino-aryl mol­ecules with at least one 2-pyridyl substit­uent on one of the nitro­gen atoms results in only two other related compounds, N-(2-bromo­benz­yl)-N′-(2-pyrid­yl)-benzene-1,2-di­amine (Manjare et al., 2009 ▸; CSD refcode RUFGIJ) and N,N′-bis­(2-pyrid­yl)benzene-1,2-di­amine (Gdaniec et al., 2004 ▸; CSD refcode ARUDEW). Both of these structures show the N—H⋯N hydrogen-bonded ring motif observed in the title compound. Inter­estingly, for N,N′-bis­(2-pyrid­yl)benzene-1,2-di­amine, the second pyridyl ring is not involved in N—H⋯N hydrogen bonding. Furthermore, the related N,N′-bis­(2-pyrid­yl)benzene-1,3-di­amine and N,N′-bis­(2-pyrid­yl)benzene-1,4-di­amine compounds (Bensemann et al., 2002 ▸; CSD refcodes XILPEN, XILPUD01; Wicher & Gdaniec, 2011 ▸; CSD refcode XILPUD02) show a greater complexity of N—H⋯N hydrogen-bonding motifs.

5. Synthesis and crystallization

N,N′-Dimethyl-1,2-phenyl­enedi­amine I and N,N′-diphenyl-1,2-phenyl­enedi­amine II were obtained from commercial sources, while compound IV was synthesized following modification of a literature procedure (Wang et al., 2013 ▸). Inter­estingly, compounds I and II are liquids and discolour easily, possibly due to the presence of residual contaminants that may be difficult to remove completely during purification. This can make purification of the ligand difficult when the R groups are small (i.e. meth­yl). Introduction of bulky aryl groups provides materials that are crystalline and can be purified easily by chromatography and recrystallization. Compound IV was synthesized by methyl­ation of commercially available N-(pyridin-2-yl)benzene-1,2-di­amine by mod­i­fying literature conditions (Wang et al., 2013 ▸) to introduce the methyl group onto the primary amine functionality. This compound was purified by chromatographic methods to afford a white solid in high purity. A suitable sample for X-ray determination was achieved by the slow diffusion of petroleum ether into a solution of IV dissolved in ethyl acetate.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. The structure was solved in the non-centrosymmetric space group Pna2₁ and refined as a racemic twin [BASF 0.3 (5)]. Hydrogen atoms attached to carbon were placed in calculated positions and refined using a riding model. The hydrogen atoms of the NH groups were located in a difference-Fourier map, and freely refined.

Table 2. Experimental details.

Crystal data
Chemical formula	C12H13N3
M r	199.25
Crystal system, space group	Orthorhombic, P n a21
Temperature (K)	123
a, b, c (Å)	13.4639 (2), 7.8555 (1), 20.1288 (3)
V (Å3)	2128.94 (5)
Z	8
Radiation type	Cu Kα
μ (mm−1)	0.60
Crystal size (mm)	0.25 × 0.13 × 0.10
Data collection
Diffractometer	Oxford Diffraction Gemini Ultra CCD
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku OD, 2015 ▸)
T min, T max	0.989, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	11852, 3104, 3018
R int	0.022
(sin θ/λ)max (Å−1)	0.596
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.029, 0.072, 1.06
No. of reflections	3104
No. of parameters	290
No. of restraints	1
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)	0.12, −0.16
Absolute structure	Refined as an inversion twin
Absolute structure parameter	0.3 (5)

Computer programs: CrysAlis PRO (Rigaku OD, 2015 ▸), SHELXT2018/3 (Sheldrick, 2015a ▸), SHELXL2018/3 (Sheldrick, 2015b ▸), X-SEED (Barbour, 2001 ▸), publCIF (Westrip, 2010 ▸).

Supplementary Material

CCDC reference: 2207385

Additional supporting information: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Crystal data

C12H13N3	Dx = 1.243 Mg m−3
Mr = 199.25	Cu Kα radiation, λ = 1.54178 Å
Orthorhombic, Pna21	Cell parameters from 6421 reflections
a = 13.4639 (2) Å	θ = 5.5–66.8°
b = 7.8555 (1) Å	µ = 0.60 mm−1
c = 20.1288 (3) Å	T = 123 K
V = 2128.94 (5) Å3	Prism, colourless
Z = 8	0.25 × 0.13 × 0.10 mm
F(000) = 848

Data collection

Oxford Diffraction Gemini Ultra CCD diffractometer	3104 independent reflections
Radiation source: fine focus sealed tube	3018 reflections with I > 2σ(I)
Detector resolution: 10.3389 pixels mm-1	Rint = 0.022
ω scans	θmax = 66.8°, θmin = 6.1°
Absorption correction: multi-scan (CrysAlisPro; Rigaku OD, 2015)	h = −16→15
Tmin = 0.989, Tmax = 1.000	k = −9→8
11852 measured reflections	l = −19→23

Refinement

Refinement on F2	Hydrogen site location: mixed
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.029	w = 1/[σ2(Fo2) + (0.0408P)2 + 0.2845P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.072	(Δ/σ)max < 0.001
S = 1.06	Δρmax = 0.12 e Å−3
3104 reflections	Δρmin = −0.16 e Å−3
290 parameters	Absolute structure: Refined as an inversion twin
1 restraint	Absolute structure parameter: 0.3 (5)

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. Refined as a 2-component inversion twin.

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

	x	y	z	Uiso*/Ueq
N1	0.05732 (12)	0.4385 (2)	0.17463 (9)	0.0216 (4)
N2	0.17895 (11)	0.6413 (2)	0.18021 (8)	0.0197 (3)
N3	−0.12863 (12)	0.4264 (2)	0.23539 (10)	0.0218 (4)
N4	0.20213 (12)	0.5712 (2)	0.32597 (9)	0.0215 (4)
N5	0.08245 (12)	0.3655 (2)	0.31899 (9)	0.0191 (3)
N6	0.38962 (12)	0.5723 (2)	0.26687 (9)	0.0213 (4)
C1	0.10475 (13)	0.5720 (2)	0.14465 (10)	0.0182 (4)
C2	0.07758 (14)	0.6353 (3)	0.08167 (10)	0.0220 (4)
H2	0.024921	0.584736	0.057237	0.026*
C3	0.12892 (16)	0.7717 (3)	0.05649 (14)	0.0276 (5)
H3A	0.111761	0.816520	0.014189	0.033*
C4	0.20612 (16)	0.8445 (3)	0.09273 (12)	0.0286 (5)
H4A	0.242660	0.938570	0.075915	0.034*
C5	0.22743 (15)	0.7749 (3)	0.15392 (12)	0.0229 (5)
H5	0.279645	0.824378	0.179112	0.027*
C6	−0.01999 (14)	0.3405 (2)	0.14590 (10)	0.0200 (4)
C7	−0.00450 (17)	0.2503 (3)	0.08767 (13)	0.0273 (5)
H7	0.058430	0.255938	0.066431	0.033*
C8	−0.07908 (18)	0.1521 (3)	0.05989 (12)	0.0325 (5)
H8	−0.068144	0.092462	0.019500	0.039*
C9	−0.17014 (17)	0.1423 (3)	0.09204 (12)	0.0316 (5)
H9	−0.221668	0.074427	0.073659	0.038*
C10	−0.18668 (15)	0.2303 (3)	0.15057 (13)	0.0244 (5)
H10	−0.249258	0.221028	0.172068	0.029*
C11	−0.11291 (14)	0.3325 (2)	0.17851 (10)	0.0192 (4)
C12	−0.21406 (16)	0.3957 (3)	0.27773 (12)	0.0297 (5)
H12A	−0.274707	0.430287	0.254431	0.045*
H12B	−0.207321	0.461959	0.318748	0.045*
H12C	−0.217817	0.274311	0.288601	0.045*
C13	0.15406 (13)	0.4378 (2)	0.35580 (10)	0.0179 (4)
C14	0.17762 (14)	0.3787 (3)	0.41966 (11)	0.0235 (4)
H14	0.228036	0.432290	0.445205	0.028*
C15	0.12622 (17)	0.2417 (3)	0.44443 (14)	0.0281 (5)
H15	0.141481	0.198837	0.487358	0.034*
C16	0.05185 (16)	0.1657 (3)	0.40675 (12)	0.0277 (5)
H16	0.015320	0.071136	0.423112	0.033*
C17	0.03327 (15)	0.2328 (3)	0.34494 (12)	0.0230 (5)
H17	−0.017626	0.181957	0.318960	0.028*
C18	0.28032 (14)	0.6664 (2)	0.35511 (10)	0.0196 (4)
C19	0.26463 (16)	0.7599 (3)	0.41236 (13)	0.0252 (5)
H19	0.200977	0.758902	0.432723	0.030*
C20	0.34067 (17)	0.8553 (3)	0.44053 (11)	0.0307 (5)
H20	0.329472	0.918276	0.480110	0.037*
C21	0.43291 (16)	0.8573 (3)	0.41021 (12)	0.0288 (5)
H21	0.485315	0.922046	0.429208	0.035*
C22	0.44960 (16)	0.7658 (3)	0.35234 (13)	0.0240 (5)
H22	0.513234	0.769323	0.331998	0.029*
C23	0.37397 (14)	0.6684 (2)	0.32350 (10)	0.0191 (4)
C24	0.47575 (16)	0.6013 (3)	0.22502 (12)	0.0289 (5)
H24A	0.470921	0.530363	0.185112	0.043*
H24B	0.536175	0.571693	0.249577	0.043*
H24C	0.478297	0.721543	0.212130	0.043*
H1	0.0701 (18)	0.421 (3)	0.2170 (14)	0.027 (7)*
H3	−0.0774 (19)	0.465 (3)	0.2568 (13)	0.026 (6)*
H4	0.1913 (19)	0.585 (3)	0.2824 (16)	0.034 (7)*
H6	0.3354 (18)	0.540 (3)	0.2465 (12)	0.022 (6)*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
N1	0.0207 (8)	0.0279 (9)	0.0160 (9)	−0.0072 (7)	−0.0018 (7)	0.0013 (7)
N2	0.0170 (7)	0.0225 (7)	0.0194 (8)	−0.0011 (6)	0.0000 (6)	−0.0029 (7)
N3	0.0195 (8)	0.0224 (9)	0.0236 (9)	−0.0020 (6)	0.0016 (7)	−0.0022 (7)
N4	0.0197 (8)	0.0283 (9)	0.0165 (9)	−0.0069 (7)	−0.0027 (7)	0.0031 (8)
N5	0.0164 (7)	0.0216 (8)	0.0192 (8)	−0.0005 (6)	0.0009 (6)	−0.0004 (7)
N6	0.0181 (8)	0.0222 (8)	0.0235 (9)	−0.0027 (6)	0.0016 (7)	−0.0012 (8)
C1	0.0161 (8)	0.0197 (9)	0.0187 (10)	0.0009 (7)	0.0028 (7)	−0.0035 (8)
C2	0.0215 (9)	0.0246 (10)	0.0197 (10)	0.0011 (8)	−0.0004 (8)	−0.0016 (9)
C3	0.0329 (12)	0.0271 (11)	0.0226 (12)	0.0000 (9)	−0.0001 (9)	0.0048 (10)
C4	0.0341 (11)	0.0241 (10)	0.0278 (12)	−0.0064 (9)	0.0034 (9)	0.0025 (9)
C5	0.0223 (9)	0.0237 (9)	0.0227 (13)	−0.0056 (8)	0.0021 (8)	−0.0027 (9)
C6	0.0204 (9)	0.0208 (9)	0.0187 (10)	−0.0035 (7)	−0.0011 (8)	0.0030 (8)
C7	0.0295 (11)	0.0301 (12)	0.0222 (13)	−0.0054 (9)	0.0028 (9)	−0.0011 (9)
C8	0.0454 (13)	0.0309 (12)	0.0212 (11)	−0.0094 (10)	−0.0003 (10)	−0.0052 (10)
C9	0.0385 (12)	0.0300 (11)	0.0263 (12)	−0.0141 (9)	−0.0099 (10)	0.0005 (10)
C10	0.0216 (9)	0.0251 (10)	0.0265 (13)	−0.0049 (8)	−0.0026 (9)	0.0056 (9)
C11	0.0207 (9)	0.0169 (9)	0.0200 (10)	0.0004 (7)	−0.0033 (8)	0.0038 (8)
C12	0.0263 (11)	0.0295 (11)	0.0333 (13)	−0.0034 (9)	0.0102 (9)	−0.0011 (10)
C13	0.0149 (8)	0.0203 (9)	0.0185 (10)	0.0010 (7)	0.0029 (7)	−0.0024 (8)
C14	0.0215 (9)	0.0266 (10)	0.0224 (10)	−0.0012 (8)	−0.0046 (8)	0.0004 (9)
C15	0.0349 (13)	0.0280 (11)	0.0213 (12)	−0.0011 (9)	−0.0042 (9)	0.0061 (9)
C16	0.0306 (10)	0.0227 (10)	0.0299 (12)	−0.0056 (8)	0.0000 (9)	0.0044 (9)
C17	0.0217 (10)	0.0204 (9)	0.0270 (14)	−0.0024 (8)	−0.0013 (8)	−0.0033 (9)
C18	0.0187 (9)	0.0220 (9)	0.0181 (10)	−0.0036 (7)	−0.0030 (8)	0.0031 (8)
C19	0.0255 (10)	0.0289 (12)	0.0213 (13)	−0.0036 (8)	0.0035 (9)	0.0002 (9)
C20	0.0373 (12)	0.0349 (11)	0.0198 (11)	−0.0098 (10)	0.0007 (9)	−0.0060 (10)
C21	0.0296 (11)	0.0317 (11)	0.0252 (11)	−0.0123 (8)	−0.0050 (9)	0.0007 (10)
C22	0.0193 (9)	0.0264 (10)	0.0264 (13)	−0.0048 (8)	−0.0028 (8)	0.0045 (9)
C23	0.0200 (9)	0.0176 (9)	0.0197 (10)	0.0001 (7)	−0.0014 (8)	0.0044 (8)
C24	0.0277 (10)	0.0276 (11)	0.0315 (12)	−0.0015 (9)	0.0111 (9)	−0.0005 (10)

Geometric parameters (Å, º)

N1—C1	1.368 (3)	C6—C7	1.386 (3)
N1—C6	1.418 (3)	C6—C11	1.414 (3)
N2—C5	1.344 (3)	C7—C8	1.384 (3)
N2—C1	1.344 (2)	C8—C9	1.389 (3)
N3—C11	1.378 (3)	C9—C10	1.384 (4)
N3—C12	1.452 (3)	C10—C11	1.395 (3)
N4—C13	1.370 (3)	C13—C14	1.403 (3)
N4—C18	1.418 (3)	C14—C15	1.373 (3)
N5—C17	1.341 (3)	C15—C16	1.391 (3)
N5—C13	1.342 (3)	C16—C17	1.374 (3)
N6—C23	1.384 (3)	C18—C19	1.383 (3)
N6—C24	1.451 (3)	C18—C23	1.412 (3)
C1—C2	1.410 (3)	C19—C20	1.390 (3)
C2—C3	1.372 (3)	C20—C21	1.384 (3)
C3—C4	1.393 (3)	C21—C22	1.387 (4)
C4—C5	1.378 (3)	C22—C23	1.400 (3)
C1—N1—C6	125.37 (18)	N3—C11—C10	122.23 (18)
C5—N2—C1	117.88 (18)	N3—C11—C6	119.83 (17)
C11—N3—C12	121.38 (17)	C10—C11—C6	117.92 (19)
C13—N4—C18	124.93 (17)	N5—C13—N4	114.92 (17)
C17—N5—C13	117.96 (18)	N5—C13—C14	121.87 (18)
C23—N6—C24	120.93 (17)	N4—C13—C14	123.21 (18)
N2—C1—N1	115.00 (17)	C15—C14—C13	118.6 (2)
N2—C1—C2	121.89 (18)	C14—C15—C16	120.1 (2)
N1—C1—C2	123.09 (18)	C17—C16—C15	117.4 (2)
C3—C2—C1	118.5 (2)	N5—C17—C16	124.1 (2)
C2—C3—C4	120.2 (2)	C19—C18—C23	120.39 (18)
C5—C4—C3	117.4 (2)	C19—C18—N4	120.74 (18)
N2—C5—C4	124.1 (2)	C23—C18—N4	118.84 (17)
C7—C6—C11	120.20 (18)	C18—C19—C20	120.9 (2)
C7—C6—N1	120.80 (18)	C21—C20—C19	119.2 (2)
C11—C6—N1	118.97 (17)	C20—C21—C22	120.64 (19)
C8—C7—C6	121.2 (2)	C21—C22—C23	120.9 (2)
C7—C8—C9	118.9 (2)	N6—C23—C22	121.96 (19)
C10—C9—C8	120.7 (2)	N6—C23—C18	120.07 (17)
C9—C10—C11	121.1 (2)	C22—C23—C18	117.95 (19)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N4—H4···N2	0.90 (3)	2.11 (3)	3.001 (3)	173 (2)
N1—H1···N5	0.88 (3)	2.11 (3)	2.981 (3)	173 (2)
N6—H6···N2	0.88 (3)	2.62 (2)	3.374 (2)	145 (2)
N3—H3···N5	0.87 (3)	2.61 (3)	3.337 (2)	142 (2)

Funding Statement

Funding for this research was provided by: CSIRO Manufacturing Flexible Electronics Theme as part of the OLED research program.