4-[4-(4-Nitro­phenyl­diazen­yl)phen­yl]hexa­nenitrile

Lu, R.; Han, L.; Zhang, M.; Wang, B.; Wang, H.

doi:10.1107/S1600536809000853

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 65| Part 2| February 2009| Page o344

doi:10.1107/S1600536809000853

Open

access

4-[4-(4-Nitrophenyldiazenyl)phenyl]hexanenitrile

Ran-zhe Lu,^a Lu-na Han,^a Min Zhang,^a Bin Wang ^a and Hai-bo Wang ^a ^*

^aCollege of Science, Nanjing University of Technology, Xinmofan Road No.5 Nanjing, Nanjing 210009, People's Republic of China
^*Correspondence e-mail: wanghaibo@njut.edu.cn

(Received 6 January 2009; accepted 8 January 2009; online 17 January 2009)

In the molecule of the title compound, C₁₈H₁₈N₄O₂, the aromatic rings are oriented at a dihedral angle of 3.72 (3)°. In the crystal structure, intermolecular C—H⋯O hydrogen bonds link the molecules into centrosymmetric dimers. There are also C—H⋯π interactions.

Related literature

For general background, see: Bach et al. (1996 ); Clark & Hester (1991 ); Taniike et al. (1996 ). For a related structure, see: Zhao et al. (2002 ). For bond-length data, see: Allen et al. (1987 ).

Experimental

Crystal data

C₁₈H₁₈N₄O₂
M_r = 322.36
Monoclinic, P 2₁ /c
a = 20.113 (4) Å
b = 10.590 (2) Å
c = 7.6820 (15) Å
β = 94.78 (3)°
V = 1630.5 (6) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 293 (2) K
0.30 × 0.20 × 0.10 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
Absorption correction: ψ scan (North et al., 1968 ) T_min = 0.964, T_max = 0.991
3037 measured reflections
2951 independent reflections
1336 reflections with I > 2σ(I)
R_int = 0.061
3 standard reflections every 200 reflections intensity decay: 1%

Refinement

R[F² > 2σ(F²)] = 0.072
wR(F²) = 0.185
S = 0.98
2951 reflections
199 parameters
62 restraints
H-atom parameters constrained
Δρ_max = 0.32 e Å⁻³
Δρ_min = −0.37 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2C⋯O1ⁱ	0.97	2.46	3.343 (6)	150
C9—H9A⋯Cg1ⁱⁱ	0.93	2.92	3.713 (6)	144
C15—H15A⋯Cg2ⁱⁱ	0.93	2.90	3.690 (6)	143
Symmetry codes: (i) -x, -y, -z+1; (ii) $[x, -y-{\script{1\over 2}}, z-{\script{1\over 2}}]$ . Cg1 and Cg2 are the centroids of the C7–C13 and C13–C18 rings, respectively.

Data collection: CAD-4 Software (Enraf–Nonius, 1989 ); cell refinement: CAD-4 Software; data reduction: XCAD4 (Harms & Wocadlo, 1995 ); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ) and PLATON (Spek, 2003 ); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Supporting information

Crystal structure: contains datablocks D, I. DOI: 10.1107/S1600536809000853/hk2611sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809000853/hk2611Isup2.hkl

checkCIF report

Comment top

The photophysical properties of azo compounds are of large interest in the development of nonlinear optical and optical data storage materials (Bach et al., 1996; Taniike et al., 1996; Clark & Hester, 1991). As part of our studies in this area, we report herein the synthesis and crystal structure of the title compound.

In the molecule of the title compound (Fig 1), the bond lengths (Allen et al., 1987) and angles are within normal ranges. Rings A (C7-C12) and B (C13-C18) are, of course, planar, and they are oriented at a dihedral angle of 3.72 (3)°.

In the crystal structure, intermolecular C-H···O hydrogen bonds (Table 1) link the molecules into centrosymmetric dimers (Fig. 2), in which they may be effective in the stabilization of the structure. There also exist C–H···π interactions (Table 1).

Related literature top

For general background, see: Bach et al. (1996); Clark & Hester (1991); Taniike et al. (1996). For a related structure, see: Zhao et al. (2002). For bond-length data, see: Allen et al. (1987). Cg1 and Cg2 are the centroids of the C7–C13 and C13–C18 rings, respectively.

Experimental top

The title compound has been synthesized according to a literature method (Zhao et al., 2002). Crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution.

Computing details top

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software (Enraf–Nonius, 1989); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

	Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.
	Fig. 2. A partial packing diagram of the title compound. Hydrogen bonds are shown as dashed lines.

(I) top

Crystal data top

C₁₈H₁₈N₄O₂	F(000) = 680
M_r = 322.36	D_x = 1.313 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 25 reflections
a = 20.113 (4) Å	θ = 9–13°
b = 10.590 (2) Å	µ = 0.09 mm⁻¹
c = 7.6820 (15) Å	T = 293 K
β = 94.78 (3)°	Block, red
V = 1630.5 (6) Å³	0.30 × 0.20 × 0.10 mm
Z = 4

Data collection top

Enraf–Nonius CAD-4 diffractometer	1336 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.061
Graphite monochromator	θ_max = 25.3°, θ_min = 1.0°
ω/2θ scans	h = 0→24
Absorption correction: ψ scan (North et al., 1968)	k = 0→12
T_min = 0.964, T_max = 0.991	l = −9→9
3037 measured reflections	3 standard reflections every 200 reflections
2951 independent reflections	intensity decay: 1%

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)] = 0.072	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.185	H-atom parameters constrained
S = 0.98	w = 1/[σ²(F_o²) + (0.060P)² + 1.P] where P = (F_o² + 2F_c²)/3
2951 reflections	(Δ/σ)_max < 0.001
199 parameters	Δρ_max = 0.32 e Å⁻³
62 restraints	Δρ_min = −0.37 e Å⁻³

Crystal data top

C₁₈H₁₈N₄O₂	V = 1630.5 (6) Å³
M_r = 322.36	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 20.113 (4) Å	µ = 0.09 mm⁻¹
b = 10.590 (2) Å	T = 293 K
c = 7.6820 (15) Å	0.30 × 0.20 × 0.10 mm
β = 94.78 (3)°

Data collection top

Enraf–Nonius CAD-4 diffractometer	1336 reflections with I > 2σ(I)
Absorption correction: ψ scan (North et al., 1968)	R_int = 0.061
T_min = 0.964, T_max = 0.991	3 standard reflections every 200 reflections
3037 measured reflections	intensity decay: 1%
2951 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.072	62 restraints
wR(F²) = 0.185	H-atom parameters constrained
S = 0.98	Δρ_max = 0.32 e Å⁻³
2951 reflections	Δρ_min = −0.37 e Å⁻³
199 parameters

Special details top

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

Refinement. 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 > 2sigma(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 (Å²) top

	x	y	z	U_iso*/U_eq
N1	0.4653 (3)	−0.1899 (5)	0.4255 (7)	0.1057 (17)
C1	0.4327 (3)	−0.1281 (7)	0.4966 (8)	0.107 (2)
O1	−0.27421 (18)	0.0779 (4)	0.7659 (5)	0.0975 (13)
O2	−0.25317 (17)	0.2141 (3)	0.9614 (5)	0.0828 (11)
N2	0.07709 (17)	0.1393 (3)	0.8661 (4)	0.0479 (7)
N3	0.03734 (18)	0.0691 (3)	0.7775 (4)	0.0506 (9)
N4	−0.2356 (2)	0.1355 (4)	0.8566 (6)	0.0658 (11)
C2	0.3903 (2)	−0.0199 (5)	0.5602 (7)	0.0829 (10)
H2B	0.4142	0.0597	0.5607	0.099*
H2C	0.3493	−0.0113	0.4853	0.099*
C3	0.3747 (2)	−0.0512 (5)	0.7350 (7)	0.0829 (10)
H3B	0.4143	−0.0822	0.8022	0.099*
H3C	0.3411	−0.1171	0.7309	0.099*
C4	0.4104 (3)	0.0772 (6)	1.1039 (8)	0.105 (2)
H4A	0.4447	0.1228	1.1719	0.157*
H4B	0.4239	−0.0091	1.0920	0.157*
H4C	0.3698	0.0801	1.1613	0.157*
C5	0.3989 (2)	0.1368 (5)	0.9246 (7)	0.0808 (17)
H5A	0.3851	0.2240	0.9360	0.097*
H5B	0.4400	0.1358	0.8671	0.097*
C6	0.3485 (2)	0.0682 (5)	0.8228 (7)	0.0829 (10)
H6A	0.3520	0.1208	0.7190	0.099*
C7	0.2832 (2)	0.0858 (4)	0.8230 (6)	0.0583 (12)
C8	0.2566 (2)	0.1767 (4)	0.9332 (5)	0.0519 (11)
H8A	0.2857	0.2281	1.0017	0.062*
C9	0.1910 (2)	0.1910 (4)	0.9421 (5)	0.0504 (11)
H9A	0.1763	0.2521	1.0169	0.060*
C10	0.1431 (2)	0.1179 (4)	0.8435 (5)	0.0479 (7)
C11	0.1685 (2)	0.0266 (4)	0.7336 (5)	0.0498 (11)
H11A	0.1390	−0.0263	0.6687	0.060*
C12	0.2337 (2)	0.0142 (4)	0.7206 (5)	0.0506 (11)
H12A	0.2479	−0.0439	0.6408	0.061*
C13	−0.0292 (2)	0.0918 (4)	0.8074 (5)	0.0470 (10)
C14	−0.0524 (2)	0.1820 (4)	0.9173 (5)	0.0511 (11)
H14A	−0.0223	0.2352	0.9798	0.061*
C15	−0.1198 (2)	0.1937 (4)	0.9352 (6)	0.0588 (12)
H15A	−0.1348	0.2540	1.0108	0.071*
C16	−0.1639 (2)	0.1184 (4)	0.8440 (5)	0.0521 (11)
C17	−0.1442 (2)	0.0243 (4)	0.7373 (6)	0.0583 (12)
H17A	−0.1753	−0.0289	0.6783	0.070*
C18	−0.0770 (2)	0.0112 (4)	0.7203 (5)	0.0618 (12)
H18A	−0.0627	−0.0528	0.6493	0.074*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.100 (4)	0.112 (4)	0.104 (4)	0.046 (3)	0.004 (3)	−0.022 (3)
C1	0.064 (4)	0.138 (6)	0.118 (5)	0.009 (4)	0.005 (3)	−0.064 (5)
O1	0.058 (2)	0.128 (3)	0.105 (3)	−0.018 (2)	−0.005 (2)	0.007 (3)
O2	0.073 (2)	0.077 (3)	0.101 (3)	0.017 (2)	0.022 (2)	0.008 (2)
N2	0.0573 (17)	0.0468 (16)	0.0392 (14)	0.0041 (14)	0.0020 (13)	0.0020 (13)
N3	0.060 (2)	0.049 (2)	0.043 (2)	0.0021 (18)	−0.0003 (17)	0.0016 (17)
N4	0.060 (3)	0.061 (3)	0.076 (3)	0.004 (2)	0.004 (2)	0.023 (2)
C2	0.069 (2)	0.093 (2)	0.086 (2)	−0.0043 (17)	−0.0003 (17)	−0.010 (2)
C3	0.069 (2)	0.093 (2)	0.086 (2)	−0.0043 (17)	−0.0003 (17)	−0.010 (2)
C4	0.086 (4)	0.112 (5)	0.111 (5)	−0.048 (4)	−0.023 (4)	0.008 (4)
C5	0.042 (3)	0.110 (4)	0.091 (4)	−0.014 (3)	0.010 (3)	−0.046 (4)
C6	0.069 (2)	0.093 (2)	0.086 (2)	−0.0043 (17)	−0.0003 (17)	−0.010 (2)
C7	0.051 (3)	0.069 (3)	0.055 (3)	−0.007 (2)	−0.001 (2)	−0.017 (2)
C8	0.055 (3)	0.040 (2)	0.061 (3)	−0.007 (2)	0.006 (2)	−0.019 (2)
C9	0.064 (3)	0.047 (3)	0.041 (2)	−0.001 (2)	0.011 (2)	−0.014 (2)
C10	0.0573 (17)	0.0468 (16)	0.0392 (14)	0.0041 (14)	0.0020 (13)	0.0020 (13)
C11	0.052 (3)	0.052 (3)	0.044 (2)	0.003 (2)	−0.003 (2)	−0.005 (2)
C12	0.056 (3)	0.044 (2)	0.052 (3)	−0.001 (2)	0.000 (2)	−0.016 (2)
C13	0.059 (3)	0.044 (2)	0.038 (2)	0.005 (2)	0.0057 (19)	0.0108 (19)
C14	0.054 (3)	0.051 (3)	0.048 (3)	0.006 (2)	−0.002 (2)	−0.005 (2)
C15	0.070 (3)	0.056 (3)	0.051 (3)	0.012 (2)	0.005 (2)	−0.005 (2)
C16	0.065 (3)	0.048 (3)	0.044 (2)	0.002 (2)	0.007 (2)	0.014 (2)
C17	0.057 (3)	0.058 (3)	0.058 (3)	−0.005 (2)	−0.005 (2)	0.003 (2)
C18	0.075 (3)	0.066 (3)	0.045 (2)	0.001 (3)	0.003 (2)	−0.007 (2)

Geometric parameters (Å, º) top

N1—C1	1.102 (6)	C6—H6A	0.9800
C1—C2	1.533 (7)	C7—C8	1.416 (5)
O1—N4	1.171 (5)	C7—C12	1.434 (5)
O2—N4	1.230 (5)	C8—C9	1.334 (5)
N2—N3	1.251 (4)	C8—H8A	0.9300
N2—C10	1.371 (5)	C9—C10	1.407 (5)
N3—C13	1.398 (5)	C9—H9A	0.9300
N4—C16	1.464 (6)	C10—C11	1.407 (5)
C2—C3	1.443 (6)	C11—C12	1.330 (5)
C2—H2B	0.9700	C11—H11A	0.9300
C2—H2C	0.9700	C12—H12A	0.9300
C3—C6	1.546 (7)	C13—C14	1.381 (5)
C3—H3B	0.9700	C13—C18	1.412 (6)
C3—H3C	0.9700	C14—C15	1.379 (5)
C4—C5	1.515 (7)	C14—H14A	0.9300
C4—H4A	0.9600	C15—C16	1.346 (6)
C4—H4B	0.9600	C15—H15A	0.9300
C4—H4C	0.9600	C16—C17	1.369 (6)
C5—C6	1.427 (6)	C17—C18	1.376 (6)
C5—H5A	0.9700	C17—H17A	0.9300
C5—H5B	0.9700	C18—H18A	0.9300
C6—C7	1.326 (6)

N1—C1—C2	166.2 (8)	C6—C7—C8	121.3 (4)
N3—N2—C10	114.5 (3)	C6—C7—C12	124.6 (4)
N2—N3—C13	112.7 (3)	C8—C7—C12	114.0 (4)
O1—N4—O2	122.0 (5)	C9—C8—C7	122.1 (4)
O1—N4—C16	120.3 (5)	C9—C8—H8A	118.9
O2—N4—C16	117.7 (5)	C7—C8—H8A	118.9
C3—C2—C1	107.1 (5)	C8—C9—C10	123.1 (4)
C3—C2—H2B	110.0	C8—C9—H9A	118.4
C1—C2—H2B	111.2	C10—C9—H9A	118.4
C3—C2—H2C	109.5	N2—C10—C9	117.9 (4)
C1—C2—H2C	110.4	N2—C10—C11	126.4 (4)
H2B—C2—H2C	108.6	C9—C10—C11	115.7 (4)
C2—C3—C6	109.1 (5)	C12—C11—C10	121.5 (4)
C2—C3—H3B	109.9	C12—C11—H11A	119.2
C6—C3—H3B	109.9	C10—C11—H11A	119.2
C2—C3—H3C	109.9	C11—C12—C7	123.4 (4)
C6—C3—H3C	109.9	C11—C12—H12A	118.3
H3B—C3—H3C	108.3	C7—C12—H12A	118.3
C5—C4—H4A	109.5	C14—C13—N3	126.6 (4)
C5—C4—H4B	109.5	C14—C13—C18	117.2 (4)
H4A—C4—H4B	109.5	N3—C13—C18	116.2 (4)
C5—C4—H4C	109.5	C15—C14—C13	120.5 (4)
H4A—C4—H4C	109.5	C15—C14—H14A	119.7
H4B—C4—H4C	109.5	C13—C14—H14A	119.7
C6—C5—C4	109.5 (5)	C16—C15—C14	120.3 (4)
C6—C5—H5A	109.8	C16—C15—H15A	119.8
C4—C5—H5A	109.8	C14—C15—H15A	119.8
C6—C5—H5B	109.8	C15—C16—C17	122.1 (4)
C4—C5—H5B	109.8	C15—C16—N4	120.1 (4)
H5A—C5—H5B	108.2	C17—C16—N4	117.7 (4)
C7—C6—C5	125.9 (5)	C16—C17—C18	117.8 (4)
C7—C6—C3	119.3 (5)	C16—C17—H17A	121.1
C5—C6—C3	113.8 (4)	C18—C17—H17A	121.1
C7—C6—H6A	93.4	C17—C18—C13	121.9 (4)
C5—C6—H6A	93.4	C17—C18—H18A	119.0
C3—C6—H6A	93.4	C13—C18—H18A	119.0

C10—N2—N3—C13	178.6 (3)	C10—C11—C12—C7	3.9 (6)
N1—C1—C2—C3	−168 (3)	C6—C7—C12—C11	174.3 (5)
C1—C2—C3—C6	165.2 (4)	C8—C7—C12—C11	−3.4 (6)
C4—C5—C6—C7	85.4 (7)	N2—N3—C13—C14	1.4 (5)
C4—C5—C6—C3	−82.7 (6)	N2—N3—C13—C18	−176.3 (3)
C2—C3—C6—C7	97.0 (6)	N3—C13—C14—C15	−179.6 (4)
C2—C3—C6—C5	−94.1 (6)	C18—C13—C14—C15	−2.0 (6)
C5—C6—C7—C8	−1.8 (9)	C13—C14—C15—C16	−0.8 (6)
C3—C6—C7—C8	165.7 (4)	C14—C15—C16—C17	3.1 (6)
C5—C6—C7—C12	−179.3 (5)	C14—C15—C16—N4	−176.9 (4)
C3—C6—C7—C12	−11.8 (8)	O1—N4—C16—C15	173.2 (4)
C6—C7—C8—C9	−176.3 (5)	O2—N4—C16—C15	−5.0 (6)
C12—C7—C8—C9	1.4 (6)	O1—N4—C16—C17	−6.8 (6)
C7—C8—C9—C10	−0.1 (7)	O2—N4—C16—C17	175.1 (4)
N3—N2—C10—C9	−178.4 (3)	C15—C16—C17—C18	−2.3 (6)
N3—N2—C10—C11	−0.3 (6)	N4—C16—C17—C18	177.6 (4)
C8—C9—C10—N2	178.7 (4)	C16—C17—C18—C13	−0.7 (6)
C8—C9—C10—C11	0.4 (6)	C14—C13—C18—C17	2.7 (6)
N2—C10—C11—C12	179.6 (4)	N3—C13—C18—C17	−179.4 (4)
C9—C10—C11—C12	−2.2 (6)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2C···O1ⁱ	0.97	2.46	3.343 (6)	150
C9—H9A···Cg1ⁱⁱ	0.93	2.92	3.713 (6)	144
C15—H15A···Cg2ⁱⁱ	0.93	2.90	3.690 (6)	143

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

Experimental details

Crystal data
Chemical formula	C₁₈H₁₈N₄O₂
M_r	322.36
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	293
a, b, c (Å)	20.113 (4), 10.590 (2), 7.6820 (15)
β (°)	94.78 (3)
V (Å³)	1630.5 (6)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.09
Crystal size (mm)	0.30 × 0.20 × 0.10

Data collection
Diffractometer	Enraf–Nonius CAD-4 diffractometer
Absorption correction	ψ scan (North et al., 1968)
T_min, T_max	0.964, 0.991
No. of measured, independent and observed [I > 2σ(I)] reflections	3037, 2951, 1336
R_int	0.061
(sin θ/λ)_max (Å⁻¹)	0.601

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.072, 0.185, 0.98
No. of reflections	2951
No. of parameters	199
No. of restraints	62
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.32, −0.37

Computer programs: CAD-4 Software (Enraf–Nonius, 1989), XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2C···O1ⁱ	0.97	2.46	3.343 (6)	150
C9—H9A···Cg1ⁱⁱ	0.93	2.92	3.713 (6)	144
C15—H15A···Cg2ⁱⁱ	0.93	2.90	3.690 (6)	143

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

References

Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19. CrossRef Web of Science Google Scholar
Bach, H., Anderle, K., Fuhrmann, Th. & Wendorff, J. H. (1996). J. Phys. Chem. 100, 4135–4140. CrossRef CAS Web of Science Google Scholar
Clark, R. J. H. & Hester, R. E. (1991). Advances in Materials Science Spectroscopy. New York: John Wiley & Sons. Google Scholar
Enraf–Nonius (1989). CAD-4 Software. Enraf–Nonius, Delft. The Netherlands. Google Scholar
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565. CrossRef IUCr Journals Google Scholar
Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany. Google Scholar
North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351–359. CrossRef IUCr Journals Web of Science Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2003). J. Appl. Cryst. 36, 7–13. Web of Science CrossRef CAS IUCr Journals Google Scholar
Taniike, K., Matsumoto, T., Sato, T., Ozaki, Y., Nakashima, K. & Iriyama, K. (1996). J. Phys. Chem. 100, 15508–15516. CrossRef CAS Web of Science Google Scholar
Zhao, X. Y., Hu, X., Yue, C. Y., Xia, X. L. & Gan, L. H. (2002). Thin Solid Films, 417, 95–100. Web of Science CrossRef CAS Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 65| Part 2| February 2009| Page o344

doi:10.1107/S1600536809000853

Open

access