supplementary materials


HTML versionpdf versioncif file3d viewstructure factorssupplementary materialsCIF check reportsimilar papers Open access

Acta Cryst. (2008). E64, o2368    [ doi:10.1107/S1600536808036842 ]

2,6-Bis[1-(2,6-diethylphenylimino)ethyl]pyridine

Y. Yang, R. Fan and W. Li

Abstract top

The title compound, C29H35N3, is the product of the condensation reaction between 2,6-diacetylpyridine and 2,6-diethylaniline. In the molecule, the pyridyl ring is coplanar with the imino functional groups [torsion angles in the range 177.1 (2)-179.9 (2)°. The two 2,6-diethyl-substituted benzene rings are approximately perpendicular to the ethylidenepyridine central core, the dihedral angles being 88.7 (1) and 88.4 (1)°, respectively.

Comment top

Luminescent coordination compounds based on pyridine-type ligands have attracted intensive attention due to their potential application in areas of sensor technologies and electro-luminescent devices (Tang & VanSlyke, 1987; Wang, 2001). In order to explore potential luminescent complexes of this type, we prepared a series of bis(iminoalkyl)pyridine ligands by the condensation of 2,6-diacetylpyridine with the corresponding aniline in methanol (Fan et al., 2004). We report here the crystal structure of one of them, (I).

The molecular structure of (I) is shown in Fig. 1 and selected bond distances are given in Table 1. The pyridyl ring is coplanar with the two imino functional groups. The two imino C═N bonds have typical double-bond characteristics, with bond lengths of 1.272 (3) and 1.275 (2) Å, which are similar to that in BIP1, 1.266 (4) (Mentes et al., 2001) and in 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine, 1.265 (2) and 1.271 (2) Å (Huang et al., 2006). Compound (I) possesses a structure which approximates Cs symmetry about a plane bisecting the central pyridyl ring. The two 2,6-diethyl-substituted phenyl rings are approximately perpendicular to the ethylidenepyridine ring, with the dihedral angles being 88.7° and 88.4°.

Related literature top

For applications of pyridine derivatives, see: Tang & VanSlyke (1987); Wang (2001). For the synthesis of the title molecule, see: Fan et al. (2004). For structures of other imino derivatives, see: Mentes et al. (2001); Huang et al. (2006).

Experimental top

The title compound was synthesized according to the literature method of Fan et al. (2004). To a solution of 2,6-diethylpyridine (1.5 g, 9.2 mmol) in absolute methanol (40 ml) was added 2,6-diethylaniline (4.6 ml, 27.7 mmol). After the addition of several drops of formic acid, the reaction mixture was refluxed for 24 h and then allowed to cool down to room temperature. The crude product precipitated as a yellow powder. Pure (I) was obtained as yellow block crystals in 84% yield (3.3 g) upon recrystallization from methanol, giving single crystals suitable for X-ray diffraction.

Refinement top

The C-bound H atoms were positioned geometrically with C—H = 0.93–0.97 Å, and allowed to ride on their parent atoms with Uiso(H) = 1.5Ueq(carrier C) for methyl groups and Uiso(H) = 1.2Ueq(carrier C) otherwise.

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. View of the molecule of (I) showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. Packing of (I) along a cell axis direction.
2,6-Bis[1-(2,6-diethylphenylimino)ethyl]pyridine top
Crystal data top
C29H35N3F(000) = 920
Mr = 425.60Dx = 1.118 Mg m−3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 13906 reflections
a = 7.9390 (8) Åθ = 1.6–26.0°
b = 12.3208 (13) ŵ = 0.07 mm−1
c = 25.998 (3) ÅT = 193 K
β = 96.234 (2)°Block, yellow
V = 2528.0 (5) Å30.26 × 0.24 × 0.20 mm
Z = 4
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer		4938 independent reflections
Radiation source: fine-focus sealed tube2362 reflections with I > 2σ(I)
graphiteRint = 0.077
φ and ω scansθmax = 26.0°, θmin = 1.6°
Absorption correction: multi-scan
(SADABS; Bruker, 1998)		h = −9→9
Tmin = 0.983, Tmax = 0.987k = −15→12
13906 measured reflectionsl = −31→32
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.057Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.101H-atom parameters constrained
S = 0.95 w = 1/[σ2(Fo2) + (0.02P)2]
where P = (Fo2 + 2Fc2)/3
4938 reflections(Δ/σ)max < 0.001
289 parametersΔρmax = 0.30 e Å−3
0 restraintsΔρmin = −0.19 e Å−3
Crystal data top
C29H35N3V = 2528.0 (5) Å3
Mr = 425.60Z = 4
Monoclinic, P21/cMo Kα radiation
a = 7.9390 (8) ŵ = 0.07 mm−1
b = 12.3208 (13) ÅT = 193 K
c = 25.998 (3) Å0.26 × 0.24 × 0.20 mm
β = 96.234 (2)°
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer		4938 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 1998)		2362 reflections with I > 2σ(I)
Tmin = 0.983, Tmax = 0.987Rint = 0.077
13906 measured reflectionsθmax = 26.0°
Refinement top
R[F2 > 2σ(F2)] = 0.057H-atom parameters constrained
wR(F2) = 0.101Δρmax = 0.30 e Å−3
S = 0.95Δρmin = −0.19 e Å−3
4938 reflectionsAbsolute structure: ?
289 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N1−0.5544 (2)0.61937 (15)−0.15400 (7)0.0377 (5)
N2−0.2647 (2)0.69242 (15)−0.04651 (7)0.0342 (5)
N30.0206 (2)0.83861 (14)0.04282 (7)0.0328 (5)
C1−0.4636 (3)0.60967 (19)−0.11083 (9)0.0353 (6)
C2−0.3645 (3)0.70650 (19)−0.09065 (9)0.0315 (6)
C3−0.3771 (3)0.80441 (18)−0.11695 (9)0.0379 (7)
H3B−0.44800.8113−0.14770.045*
C4−0.2830 (3)0.89137 (19)−0.09692 (9)0.0401 (7)
H4A−0.28930.9580−0.11390.048*
C5−0.1790 (3)0.87807 (18)−0.05110 (9)0.0346 (6)
H5A−0.11400.9355−0.03670.041*
C6−0.1734 (3)0.77816 (18)−0.02709 (9)0.0321 (6)
C7−0.0646 (3)0.75836 (19)0.02294 (9)0.0328 (6)
C8−0.4473 (3)0.50849 (18)−0.07891 (9)0.0551 (8)
H8A−0.51660.4524−0.09590.083*
H8B−0.48370.5227−0.04550.083*
H8C−0.33110.4854−0.07480.083*
C9−0.0684 (3)0.64705 (18)0.04624 (9)0.0516 (8)
H9A0.00570.64500.07800.077*
H9B−0.03140.59470.02250.077*
H9C−0.18180.63020.05310.077*
C10−0.6522 (3)0.52973 (18)−0.17576 (9)0.0350 (6)
C11−0.5797 (3)0.46024 (19)−0.20928 (9)0.0354 (6)
C12−0.6793 (3)0.3774 (2)−0.23284 (9)0.0460 (7)
H12A−0.63390.3312−0.25600.055*
C13−0.8439 (4)0.3630 (2)−0.22238 (10)0.0529 (8)
H13A−0.90890.3071−0.23820.063*
C14−0.9118 (3)0.4313 (2)−0.18850 (10)0.0531 (8)
H14A−1.02270.4202−0.18130.064*
C15−0.8197 (3)0.5162 (2)−0.16479 (10)0.0442 (7)
C16−0.3966 (3)0.4759 (2)−0.21860 (9)0.0542 (8)
H16A−0.37380.5533−0.21860.065*
H16B−0.32610.4447−0.18950.065*
C17−0.3415 (3)0.4290 (2)−0.26723 (10)0.0677 (9)
H17A−0.22330.4437−0.26850.102*
H17B−0.40610.4613−0.29670.102*
H17C−0.35990.3520−0.26770.102*
C18−0.8989 (3)0.5920 (2)−0.12862 (10)0.0595 (8)
H18A−0.99460.5565−0.11550.071*
H18B−0.81670.6094−0.09940.071*
C19−0.9567 (4)0.6936 (2)−0.15592 (11)0.0843 (11)
H19A−1.00650.7408−0.13240.126*
H19B−1.03920.6764−0.18450.126*
H19C−0.86160.7292−0.16850.126*
C200.1215 (3)0.82874 (17)0.09135 (9)0.0314 (6)
C210.2917 (3)0.79922 (18)0.09253 (10)0.0366 (6)
C220.3912 (3)0.80093 (19)0.14006 (11)0.0481 (7)
H22A0.50450.78060.14170.058*
C230.3256 (4)0.8321 (2)0.18473 (11)0.0512 (8)
H23A0.39470.83470.21600.061*
C240.1569 (4)0.85952 (19)0.18268 (10)0.0466 (7)
H24A0.11290.87990.21300.056*
C250.0504 (3)0.85759 (18)0.13639 (9)0.0367 (6)
C260.3694 (3)0.76989 (19)0.04370 (9)0.0458 (7)
H26A0.29240.72250.02270.055*
H26B0.47380.73020.05300.055*
C270.4070 (3)0.86848 (19)0.01206 (10)0.0595 (8)
H27A0.45470.8456−0.01850.089*
H27B0.48620.91460.03230.089*
H27C0.30400.90770.00240.089*
C28−0.1336 (3)0.8865 (2)0.13489 (9)0.0482 (7)
H28A−0.16700.88120.16960.058*
H28B−0.19990.83420.11340.058*
C29−0.1747 (4)0.9995 (2)0.11419 (10)0.0685 (9)
H29A−0.29381.01310.11420.103*
H29B−0.14471.00510.07950.103*
H29C−0.11171.05200.13570.103*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0406 (14)0.0347 (13)0.0358 (13)−0.0017 (10)−0.0047 (11)−0.0046 (10)
N20.0406 (14)0.0297 (12)0.0312 (12)−0.0026 (10)−0.0010 (10)−0.0022 (10)
N30.0371 (13)0.0301 (12)0.0309 (12)−0.0024 (10)0.0030 (10)−0.0034 (10)
C10.0411 (17)0.0318 (15)0.0320 (15)0.0018 (12)−0.0001 (13)−0.0012 (12)
C20.0369 (16)0.0278 (15)0.0293 (15)0.0002 (12)0.0020 (12)−0.0022 (12)
C30.0455 (18)0.0329 (15)0.0340 (15)−0.0013 (13)−0.0009 (13)−0.0007 (13)
C40.0536 (18)0.0265 (15)0.0396 (16)−0.0012 (13)0.0026 (14)0.0026 (12)
C50.0408 (16)0.0291 (15)0.0337 (15)−0.0042 (12)0.0029 (13)−0.0028 (12)
C60.0357 (16)0.0269 (14)0.0337 (15)−0.0014 (12)0.0044 (12)−0.0011 (12)
C70.0369 (16)0.0295 (15)0.0318 (15)−0.0001 (12)0.0039 (13)0.0007 (12)
C80.072 (2)0.0370 (16)0.0509 (18)−0.0122 (15)−0.0163 (16)0.0078 (14)
C90.064 (2)0.0381 (16)0.0479 (17)−0.0114 (14)−0.0170 (15)0.0096 (14)
C100.0386 (17)0.0332 (15)0.0311 (15)−0.0026 (13)−0.0057 (13)0.0008 (12)
C110.0316 (16)0.0389 (16)0.0344 (15)−0.0021 (13)−0.0021 (13)−0.0005 (13)
C120.053 (2)0.0466 (17)0.0372 (16)−0.0019 (15)−0.0017 (14)−0.0079 (13)
C130.052 (2)0.055 (2)0.0492 (18)−0.0161 (16)−0.0035 (16)−0.0064 (15)
C140.0335 (18)0.071 (2)0.0537 (19)−0.0119 (16)0.0004 (15)−0.0030 (17)
C150.0375 (18)0.0504 (18)0.0439 (17)0.0016 (14)0.0000 (14)−0.0038 (14)
C160.0444 (19)0.071 (2)0.0471 (18)0.0011 (15)0.0047 (14)−0.0214 (15)
C170.063 (2)0.087 (2)0.054 (2)0.0008 (18)0.0091 (16)−0.0043 (17)
C180.049 (2)0.061 (2)0.070 (2)0.0079 (16)0.0126 (16)0.0072 (17)
C190.110 (3)0.054 (2)0.096 (3)0.007 (2)0.042 (2)0.006 (2)
C200.0345 (16)0.0256 (14)0.0327 (15)−0.0062 (12)−0.0028 (13)0.0009 (11)
C210.0391 (17)0.0291 (15)0.0410 (16)−0.0041 (12)0.0016 (14)0.0062 (12)
C220.0389 (18)0.0431 (17)0.060 (2)−0.0043 (13)−0.0057 (16)0.0111 (15)
C230.056 (2)0.0497 (18)0.0442 (19)−0.0110 (16)−0.0113 (16)0.0052 (15)
C240.062 (2)0.0439 (17)0.0340 (16)−0.0109 (15)0.0035 (15)−0.0012 (13)
C250.0407 (17)0.0341 (15)0.0351 (16)−0.0057 (13)0.0038 (14)0.0008 (12)
C260.0416 (18)0.0397 (16)0.0567 (18)0.0045 (13)0.0072 (14)0.0047 (14)
C270.070 (2)0.0473 (18)0.066 (2)0.0092 (15)0.0282 (17)0.0120 (15)
C280.051 (2)0.0554 (19)0.0396 (16)−0.0051 (15)0.0118 (14)−0.0067 (14)
C290.064 (2)0.076 (2)0.068 (2)0.0192 (17)0.0232 (17)0.0168 (18)
Geometric parameters (Å, °) top
N1—C11.272 (3)C16—H16A0.9700
N1—C101.431 (3)C16—H16B0.9700
N2—C21.333 (2)C17—H17A0.9600
N2—C61.348 (2)C17—H17B0.9600
N3—C71.275 (2)C17—H17C0.9600
N3—C201.424 (3)C18—C191.486 (3)
C1—C21.493 (3)C18—H18A0.9700
C1—C81.495 (3)C18—H18B0.9700
C2—C31.385 (3)C19—H19A0.9600
C3—C41.376 (3)C19—H19B0.9600
C3—H3B0.9300C19—H19C0.9600
C4—C51.383 (3)C20—C211.397 (3)
C4—H4A0.9300C20—C251.400 (3)
C5—C61.379 (3)C21—C221.393 (3)
C5—H5A0.9300C21—C261.514 (3)
C6—C71.501 (3)C22—C231.378 (3)
C7—C91.501 (3)C22—H22A0.9300
C8—H8A0.9600C23—C241.376 (3)
C8—H8B0.9600C23—H23A0.9300
C8—H8C0.9600C24—C251.394 (3)
C9—H9A0.9600C24—H24A0.9300
C9—H9B0.9600C25—C281.500 (3)
C9—H9C0.9600C26—C271.515 (3)
C10—C111.390 (3)C26—H26A0.9700
C10—C151.399 (3)C26—H26B0.9700
C11—C121.391 (3)C27—H27A0.9600
C11—C161.511 (3)C27—H27B0.9600
C12—C131.375 (3)C27—H27C0.9600
C12—H12A0.9300C28—C291.515 (3)
C13—C141.370 (3)C28—H28A0.9700
C13—H13A0.9300C28—H28B0.9700
C14—C151.383 (3)C29—H29A0.9600
C14—H14A0.9300C29—H29B0.9600
C15—C181.511 (3)C29—H29C0.9600
C16—C171.498 (3)
C1—N1—C10120.5 (2)C16—C17—H17A109.5
C2—N2—C6117.7 (2)C16—C17—H17B109.5
C7—N3—C20121.0 (2)H17A—C17—H17B109.5
N1—C1—C2117.5 (2)C16—C17—H17C109.5
N1—C1—C8125.1 (2)H17A—C17—H17C109.5
C2—C1—C8117.4 (2)H17B—C17—H17C109.5
N2—C2—C3122.9 (2)C19—C18—C15110.6 (2)
N2—C2—C1116.1 (2)C19—C18—H18A109.5
C3—C2—C1121.0 (2)C15—C18—H18A109.5
C4—C3—C2119.0 (2)C19—C18—H18B109.5
C4—C3—H3B120.5C15—C18—H18B109.5
C2—C3—H3B120.5H18A—C18—H18B108.1
C3—C4—C5118.8 (2)C18—C19—H19A109.5
C3—C4—H4A120.6C18—C19—H19B109.5
C5—C4—H4A120.6H19A—C19—H19B109.5
C6—C5—C4118.9 (2)C18—C19—H19C109.5
C6—C5—H5A120.6H19A—C19—H19C109.5
C4—C5—H5A120.6H19B—C19—H19C109.5
N2—C6—C5122.7 (2)C21—C20—C25121.7 (2)
N2—C6—C7115.6 (2)C21—C20—N3119.4 (2)
C5—C6—C7121.7 (2)C25—C20—N3118.7 (2)
N3—C7—C6117.1 (2)C22—C21—C20118.0 (2)
N3—C7—C9125.3 (2)C22—C21—C26120.3 (2)
C6—C7—C9117.6 (2)C20—C21—C26121.7 (2)
C1—C8—H8A109.5C23—C22—C21121.5 (3)
C1—C8—H8B109.5C23—C22—H22A119.3
H8A—C8—H8B109.5C21—C22—H22A119.3
C1—C8—H8C109.5C24—C23—C22119.4 (3)
H8A—C8—H8C109.5C24—C23—H23A120.3
H8B—C8—H8C109.5C22—C23—H23A120.3
C7—C9—H9A109.5C23—C24—C25121.7 (3)
C7—C9—H9B109.5C23—C24—H24A119.1
H9A—C9—H9B109.5C25—C24—H24A119.1
C7—C9—H9C109.5C24—C25—C20117.7 (2)
H9A—C9—H9C109.5C24—C25—C28121.1 (2)
H9B—C9—H9C109.5C20—C25—C28121.2 (2)
C11—C10—C15121.4 (2)C21—C26—C27112.7 (2)
C11—C10—N1118.6 (2)C21—C26—H26A109.0
C15—C10—N1119.9 (2)C27—C26—H26A109.0
C10—C11—C12118.2 (2)C21—C26—H26B109.0
C10—C11—C16119.5 (2)C27—C26—H26B109.0
C12—C11—C16122.2 (2)H26A—C26—H26B107.8
C13—C12—C11121.0 (3)C26—C27—H27A109.5
C13—C12—H12A119.5C26—C27—H27B109.5
C11—C12—H12A119.5H27A—C27—H27B109.5
C14—C13—C12119.8 (3)C26—C27—H27C109.5
C14—C13—H13A120.1H27A—C27—H27C109.5
C12—C13—H13A120.1H27B—C27—H27C109.5
C13—C14—C15121.7 (3)C25—C28—C29113.5 (2)
C13—C14—H14A119.2C25—C28—H28A108.9
C15—C14—H14A119.2C29—C28—H28A108.9
C14—C15—C10117.9 (2)C25—C28—H28B108.9
C14—C15—C18120.7 (3)C29—C28—H28B108.9
C10—C15—C18121.4 (2)H28A—C28—H28B107.7
C17—C16—C11117.4 (2)C28—C29—H29A109.5
C17—C16—H16A108.0C28—C29—H29B109.5
C11—C16—H16A108.0H29A—C29—H29B109.5
C17—C16—H16B108.0C28—C29—H29C109.5
C11—C16—H16B108.0H29A—C29—H29C109.5
H16A—C16—H16B107.2H29B—C29—H29C109.5
C10—N1—C1—C2179.8 (2)C12—C13—C14—C151.0 (4)
C10—N1—C1—C80.3 (4)C13—C14—C15—C10−1.0 (4)
C6—N2—C2—C30.2 (3)C13—C14—C15—C18178.4 (2)
C6—N2—C2—C1−179.9 (2)C11—C10—C15—C14−0.2 (4)
N1—C1—C2—N2−177.1 (2)N1—C10—C15—C14177.2 (2)
C8—C1—C2—N22.4 (3)C11—C10—C15—C18−179.6 (2)
N1—C1—C2—C32.8 (3)N1—C10—C15—C18−2.3 (4)
C8—C1—C2—C3−177.7 (2)C10—C11—C16—C17−158.5 (2)
N2—C2—C3—C40.0 (4)C12—C11—C16—C1722.1 (4)
C1—C2—C3—C4−179.9 (2)C14—C15—C18—C19−98.9 (3)
C2—C3—C4—C50.0 (4)C10—C15—C18—C1980.6 (3)
C3—C4—C5—C6−0.1 (3)C7—N3—C20—C2191.8 (3)
C2—N2—C6—C5−0.3 (3)C7—N3—C20—C25−93.3 (3)
C2—N2—C6—C7179.4 (2)C25—C20—C21—C22−1.1 (3)
C4—C5—C6—N20.3 (3)N3—C20—C21—C22173.6 (2)
C4—C5—C6—C7−179.4 (2)C25—C20—C21—C26−178.9 (2)
C20—N3—C7—C6177.2 (2)N3—C20—C21—C26−4.2 (3)
C20—N3—C7—C9−1.0 (4)C20—C21—C22—C23−0.9 (4)
N2—C6—C7—N3−178.6 (2)C26—C21—C22—C23177.0 (2)
C5—C6—C7—N31.1 (3)C21—C22—C23—C241.7 (4)
N2—C6—C7—C9−0.2 (3)C22—C23—C24—C25−0.6 (4)
C5—C6—C7—C9179.5 (2)C23—C24—C25—C20−1.3 (4)
C1—N1—C10—C11−91.4 (3)C23—C24—C25—C28179.4 (2)
C1—N1—C10—C1591.2 (3)C21—C20—C25—C242.1 (3)
C15—C10—C11—C121.4 (3)N3—C20—C25—C24−172.6 (2)
N1—C10—C11—C12−175.95 (19)C21—C20—C25—C28−178.5 (2)
C15—C10—C11—C16−178.0 (2)N3—C20—C25—C286.8 (3)
N1—C10—C11—C164.6 (3)C22—C21—C26—C27−100.8 (3)
C10—C11—C12—C13−1.5 (4)C20—C21—C26—C2777.0 (3)
C16—C11—C12—C13177.9 (2)C24—C25—C28—C29102.6 (3)
C11—C12—C13—C140.3 (4)C20—C25—C28—C29−76.7 (3)
Table 1
Selected geometric parameters (Å) top
N1—C11.272 (3)N2—C61.348 (2)
N1—C101.431 (3)N3—C71.275 (2)
N2—C21.333 (2)N3—C201.424 (3)
Acknowledgements top

This work was supported by the National Natural Science Foundation of China (20671025 and 20771030), Young Foundation of Heilongjiang Province in China (QC06C029), Heilongjiang Natural Science Foundation (B200603) and Science Innovation Special Foundation of Harbin City, China (2006RFQXG037).

references
References top

Bruker (1998). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.

Fan, R.-Q., Zhu, D.-S., Mu, Y., Li, G.-H., Yang, Y.-L., Su, Q. & Feng, S.-H. (2004). Eur. J. Inorg. Chem. pp. 4891–4897.

Huang, Y.-B., Ma, X.-L., Zheng, S.-N., Chen, J.-X. & Wei, C.-X. (2006). Acta Cryst. E62, o3044–o3045.

Mentes, A., Fawcett, J. & Kemmitt, R. D. W. (2001). Acta Cryst. E57, o424–o425.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Tang, C. W. & VanSlyke, S. A. (1987). Appl. Phys. Lett. 51, 913–915.

Wang, S. (2001). Coord. Chem. Rev. 215, 79–98.