(E)-2-[4-(Dimethyl­amino)­styr­yl]-1-methyl­pyridinium triiodide

Fun, H.-K.; Chanawanno, K.; Chantrapromma, S.

doi:10.1107/S1600536811028753

organic compounds

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ISSN: 2056-9890

Volume 67| Part 8| August 2011| Page o2151

doi:10.1107/S1600536811028753

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(E)-2-[4-(Dimethylamino)styryl]-1-methylpyridinium triiodide

Hoong-Kun Fun,^a ^*‡ Kullapa Chanawanno ^b and Suchada Chantrapromma ^b §

^aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, and ^bCrystal Materials Research Unit, Department of Chemistry, Faculty of Science, Prince of Songkla University, Hat-Yai, Songkhla 90112, Thailand
^*Correspondence e-mail: hkfun@usm.my

(Received 14 July 2011; accepted 17 July 2011; online 30 July 2011)

The asymmetric unit of the title compound, C₁₆H₁₉N₂⁺·I₃⁻, contains a (E)-2-[4-(dimethylamino)styryl)-1-methylpyridinium cation and half each of two triiodide anions. The complete triiodide anions are each generated by inversion symmetry. The planar cation has all of its eighteen non-H atoms situated on a mirror plane. In the crystal, the cations are stacked along the b axis by π–π interactions with a centroid–centroid distance of 3.5757 (13) Å. The triiodide anions are located between the cations. The crystal structure is further consolidated by short C⋯C [3.322 (9)–3.3952 (19) Å] contacts.

Related literature

For background to and applications of pyridinium compounds, see: Chanawanno et al. (2010 ); Fisicaro et al. (1990 ); Pernak et al. (2001 ). For related structures, see: Chantrapromma et al. (2010 ); Zhang et al. (2008 ). For standard bond lengths, see: Allen et al. (1987 ). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 ).

Experimental

Crystal data

C₁₆H₁₉N₂⁺·I₃⁻
M_r = 620.03
Monoclinic, C 2/m
a = 19.8760 (3) Å
b = 6.6126 (1) Å
c = 14.4421 (2) Å
β = 95.107 (1)°
V = 1890.62 (5) Å³
Z = 4
Mo Kα radiation
μ = 4.96 mm⁻¹
T = 100 K
0.45 × 0.15 × 0.04 mm

Data collection

Bruker APEX DUO CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ) T_min = 0.212, T_max = 0.838
16143 measured reflections
2484 independent reflections
2263 reflections with I > 2σ(I)
R_int = 0.030

Refinement

R[F² > 2σ(F²)] = 0.030
wR(F²) = 0.079
S = 1.04
2484 reflections
129 parameters
H-atom parameters constrained
Δρ_max = 1.74 e Å⁻³
Δρ_min = −0.60 e Å⁻³

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811028753/sj5182sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811028753/sj5182Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811028753/sj5182Isup3.cml

checkCIF report

Comment top

Pyridinium halide salts, generally possess surface active and interesting antimicrobial properties. They contain reactive functional groups covalently bound to the long hydrophobic chain and can exhibit biological activity (Fisicaro et al., 1990; Chanawanno et al., 2010). It has been proven that one of the factors which control their antimicrobial activity is the presence of anions in the compounds. In the work done by Pernak and coworkers, it was shown that the various anion types can exhibit different antimicrobial activities (Pernak et al., 2001). As our ongoing research is aimed at enhancing the antimicrobial activity of pyridinium salts, we have synthesized pyridinium salts with various anions in order to investigate the relationship between the types of anion and their antimicrobial properties. In the course of this work, the title compound (I) was synthesized and its crystal structure is reported here.

Fig. 1 shows the molecular structure of the title compound (I); the asymmetric unit consists of a C₁₆H₁₉N₂⁺ cation and two half-I₃^- anions. The complete molecule of one triiodide anion (I2A) is generated by a crystallographic symmetry centre 1 - x, y, -z whereas the other (I4A) is by 1 - x, y, 1 - z. The cation is 100% planar as all its eighteen non-hydrogen atoms lie on a mirror plane, x, 0, z. One H atom of each of its three methyl groups at C14, C15 and C16 also lies in the mirror plane. The cation exists in an E configuration with respect to the C6═C7 double bond [1.327 (8) Å] and the torsion angles C5–C6–C7–C8 = 180.000 (3)°. The bond lengths (Allen et al., 1987) and angles in (I) are in normal ranges and comparable to those found in related structures (Chantrapromma et al., 2010; Zhang et al., 2008).

In the crystal packing (Fig. 2) the cations are stacked along the b axis by π···π interactions with the distances Cg₁···Cg₂ = 3.5757 (13) Å (symmetry codes: 1/2 - x, -1/2 + y, 2 - z; 1/2 - x, 1/2 + y, 2 - z; 1/2 - x, -1/2 - y, 2 - z and 1/2 - x, 1/2 - y, 2 - z); Cg₁ and Cg₂ are the centroids of the C1–C5/N1 and C8–C13, respectively. Triiodide anions are located in the interstitials of the cations. The crystal structure is further consolidated by these π···π interactions and short C···C [3.322 (9)–3.3952 (19)Å] contacts.

Related literature top

For background to and applications of pyridinium compounds, see: Chanawanno et al. (2010); Fisicaro et al. (1990); Pernak et al. (2001). For related structures, see: Chantrapromma et al. (2010); Zhang et al. (2008). For standard bond lengths, see: Allen et al. (1987). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986).

Experimental top

The title compound was synthesized by mixing a solution of (E)-2-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (Zhang et al., 2008) (0.20 g, 0.55 mmol) in hot methanol (50 ml) and a solution of CuI₂ (0.17 g, 0.55 mmol) in hot methanol (30 ml). The mixture was stirred for half an hour and then left at room temperature. The title compound was formed as a red solid after 2 days. Orange needle-shaped single crystals suitable for x-ray structure determination were obtained by recrystallization from ethanol by slow evaporation of the solvent at ambient temperature over several days, M.p. >573 K.

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top

	Fig. 1. The asymmetric unit of (I) showing 50% probability displacement ellipsoids and the atom-numbering scheme. Atoms I2A and I4A were generated by symmetry codes 1 - x, y, -z and 1 - x, y, 1 - z, respectively whereas one of the three H atoms on each of the three methyl groups are generated by symmetry code x, -y, z.
	Fig. 2. The crystal packing of (I) viewed along the b axis.

(E)-2-[4-(Dimethylamino)styryl]-1-methylpyridinium triiodide top

Crystal data top

C₁₆H₁₉N₂⁺·I₃⁻	F(000) = 1152
M_r = 620.03	D_x = 2.178 Mg m⁻³
Monoclinic, C2/m	Melting point > 537 K
Hall symbol: -C 2y	Mo Kα radiation, λ = 0.71073 Å
a = 19.8760 (3) Å	Cell parameters from 2484 reflections
b = 6.6126 (1) Å	θ = 1.4–28.0°
c = 14.4421 (2) Å	µ = 4.96 mm⁻¹
β = 95.107 (1)°	T = 100 K
V = 1890.62 (5) Å³	Needle, orange
Z = 4	0.45 × 0.15 × 0.04 mm

Data collection top

Bruker APEX DUO CCD area-detector diffractometer	2484 independent reflections
Radiation source: sealed tube	2263 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.030
ϕ and ω scans	θ_max = 28.0°, θ_min = 1.4°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −26→26
T_min = 0.212, T_max = 0.838	k = −8→8
16143 measured reflections	l = −19→18

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)] = 0.030	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.079	H-atom parameters constrained
S = 1.04	w = 1/[σ²(F_o²) + (0.0387P)² + 13.6577P] where P = (F_o² + 2F_c²)/3
2484 reflections	(Δ/σ)_max = 0.001
129 parameters	Δρ_max = 1.74 e Å⁻³
0 restraints	Δρ_min = −0.60 e Å⁻³

Crystal data top

C₁₆H₁₉N₂⁺·I₃⁻	V = 1890.62 (5) Å³
M_r = 620.03	Z = 4
Monoclinic, C2/m	Mo Kα radiation
a = 19.8760 (3) Å	µ = 4.96 mm⁻¹
b = 6.6126 (1) Å	T = 100 K
c = 14.4421 (2) Å	0.45 × 0.15 × 0.04 mm
β = 95.107 (1)°

Data collection top

Bruker APEX DUO CCD area-detector diffractometer	2484 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2009)	2263 reflections with I > 2σ(I)
T_min = 0.212, T_max = 0.838	R_int = 0.030
16143 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.030	0 restraints
wR(F²) = 0.079	H-atom parameters constrained
S = 1.04	w = 1/[σ²(F_o²) + (0.0387P)² + 13.6577P] where P = (F_o² + 2F_c²)/3
2484 reflections	Δρ_max = 1.74 e Å⁻³
129 parameters	Δρ_min = −0.60 e Å⁻³

Special details top

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.

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.

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

	x	y	z	U_iso*/U_eq
I1	0.5000	0.5000	0.0000	0.02351 (12)
I2	0.424696 (18)	0.5000	0.16345 (3)	0.03339 (11)
I3	0.5000	0.5000	0.5000	0.03354 (14)
I4	0.35817 (2)	0.5000	0.42352 (3)	0.03813 (12)
N1	0.2700 (3)	0.0000	1.2529 (3)	0.0300 (10)
N2	0.4157 (3)	0.0000	0.6794 (4)	0.0393 (12)
C1	0.2277 (3)	0.0000	1.3233 (4)	0.0338 (13)
H1A	0.2472	0.0000	1.3858	0.041*
C2	0.1609 (3)	0.0000	1.3078 (4)	0.0356 (13)
H2A	0.1331	0.0000	1.3580	0.043*
C3	0.1319 (3)	0.0000	1.2140 (4)	0.0329 (12)
H3A	0.0842	0.0000	1.2007	0.039*
C4	0.1724 (3)	0.0000	1.1446 (4)	0.0319 (12)
H4A	0.1530	0.0000	1.0820	0.038*
C5	0.2453 (3)	0.0000	1.1631 (4)	0.0288 (11)
C6	0.2883 (3)	0.0000	1.0881 (4)	0.0255 (10)
H6A	0.3355	0.0000	1.1052	0.031*
C7	0.2692 (3)	0.0000	0.9977 (4)	0.0275 (11)
H7A	0.2218	0.0000	0.9817	0.033*
C8	0.3107 (3)	0.0000	0.9192 (4)	0.0290 (11)
C9	0.2775 (3)	0.0000	0.8304 (4)	0.0289 (11)
H9A	0.2295	0.0000	0.8240	0.035*
C10	0.3105 (3)	0.0000	0.7535 (4)	0.0272 (11)
H10A	0.2852	0.0000	0.6945	0.033*
C11	0.3815 (3)	0.0000	0.7579 (4)	0.0232 (10)
C12	0.4171 (3)	0.0000	0.8475 (4)	0.0272 (11)
H12A	0.4651	0.0000	0.8536	0.033*
C13	0.3818 (3)	0.0000	0.9268 (4)	0.0336 (12)
H13A	0.4059	0.0000	0.9866	0.040*
C14	0.3424 (3)	0.0000	1.2755 (5)	0.0361 (13)
H14A	0.3599	0.1166	1.2461	0.043*
H14B	0.3546	0.0000	1.3414	0.043*
C15	0.3804 (4)	0.0000	0.5885 (4)	0.0391 (14)
H15A	0.3516	0.1166	0.5844	0.047*
H15B	0.4110	0.0000	0.5407	0.047*
C16	0.4903 (3)	0.0000	0.6862 (5)	0.0460 (16)
H16A	0.5052	0.1166	0.7219	0.055*
H16B	0.5073	0.0000	0.6261	0.055*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
I1	0.0208 (2)	0.0210 (2)	0.0277 (2)	0.000	−0.00351 (16)	0.000
I2	0.03043 (19)	0.0368 (2)	0.0338 (2)	0.000	0.00747 (14)	0.000
I3	0.0526 (3)	0.0261 (3)	0.0232 (2)	0.000	0.0100 (2)	0.000
I4	0.0541 (3)	0.0367 (2)	0.02383 (19)	0.000	0.00475 (16)	0.000
N1	0.038 (2)	0.023 (2)	0.028 (2)	0.000	−0.0003 (19)	0.000
N2	0.047 (3)	0.044 (3)	0.028 (2)	0.000	0.011 (2)	0.000
C1	0.059 (4)	0.018 (2)	0.026 (3)	0.000	0.014 (2)	0.000
C2	0.054 (4)	0.023 (3)	0.031 (3)	0.000	0.010 (3)	0.000
C3	0.038 (3)	0.023 (3)	0.037 (3)	0.000	0.002 (2)	0.000
C4	0.052 (3)	0.020 (2)	0.022 (2)	0.000	−0.005 (2)	0.000
C5	0.050 (3)	0.015 (2)	0.023 (2)	0.000	0.011 (2)	0.000
C6	0.036 (3)	0.017 (2)	0.024 (2)	0.000	0.004 (2)	0.000
C7	0.033 (3)	0.022 (2)	0.027 (3)	0.000	0.002 (2)	0.000
C8	0.039 (3)	0.017 (2)	0.034 (3)	0.000	0.013 (2)	0.000
C9	0.026 (2)	0.017 (2)	0.044 (3)	0.000	0.005 (2)	0.000
C10	0.027 (2)	0.017 (2)	0.036 (3)	0.000	−0.008 (2)	0.000
C11	0.033 (3)	0.017 (2)	0.021 (2)	0.000	0.0046 (19)	0.000
C12	0.025 (2)	0.025 (3)	0.030 (3)	0.000	−0.003 (2)	0.000
C13	0.052 (3)	0.025 (3)	0.022 (3)	0.000	−0.008 (2)	0.000
C14	0.040 (3)	0.030 (3)	0.038 (3)	0.000	0.005 (2)	0.000
C15	0.052 (4)	0.037 (3)	0.028 (3)	0.000	0.004 (3)	0.000
C16	0.040 (3)	0.056 (4)	0.044 (4)	0.000	0.015 (3)	0.000

Geometric parameters (Å, º) top

I1—I2ⁱ	2.9054 (4)	C6—H6A	0.9500
I1—I2	2.9054 (4)	C7—C8	1.459 (8)
I3—I4	2.9347 (4)	C7—H7A	0.9500
I3—I4ⁱⁱ	2.9347 (4)	C8—C9	1.389 (8)
N1—C5	1.346 (7)	C8—C13	1.407 (9)
N1—C1	1.375 (7)	C9—C10	1.339 (8)
N1—C14	1.448 (8)	C9—H9A	0.9500
N2—C11	1.373 (7)	C10—C11	1.407 (7)
N2—C15	1.433 (8)	C10—H10A	0.9500
N2—C16	1.476 (9)	C11—C12	1.420 (7)
C1—C2	1.327 (9)	C12—C13	1.396 (8)
C1—H1A	0.9500	C12—H12A	0.9500
C2—C3	1.425 (9)	C13—H13A	0.9500
C2—H2A	0.9500	C14—H14A	0.9601
C3—C4	1.341 (9)	C14—H14B	0.9600
C3—H3A	0.9500	C15—H15A	0.9600
C4—C5	1.449 (9)	C15—H15B	0.9598
C4—H4A	0.9500	C16—H16A	0.9600
C5—C6	1.438 (7)	C16—H16B	0.9600
C6—C7	1.327 (8)

I2ⁱ—I1—I2	180.000 (12)	C8—C7—H7A	115.4
I4—I3—I4ⁱⁱ	180.0	C9—C8—C13	117.6 (5)
C5—N1—C1	121.2 (5)	C9—C8—C7	117.5 (5)
C5—N1—C14	119.2 (5)	C13—C8—C7	124.9 (5)
C1—N1—C14	119.6 (5)	C10—C9—C8	122.6 (5)
C11—N2—C15	121.2 (5)	C10—C9—H9A	118.7
C11—N2—C16	120.9 (5)	C8—C9—H9A	118.7
C15—N2—C16	117.9 (5)	C9—C10—C11	121.7 (5)
C2—C1—N1	122.9 (6)	C9—C10—H10A	119.2
C2—C1—H1A	118.6	C11—C10—H10A	119.2
N1—C1—H1A	118.6	N2—C11—C10	122.2 (5)
C1—C2—C3	118.4 (6)	N2—C11—C12	120.6 (5)
C1—C2—H2A	120.8	C10—C11—C12	117.3 (5)
C3—C2—H2A	120.8	C13—C12—C11	120.1 (5)
C4—C3—C2	119.4 (6)	C13—C12—H12A	120.0
C4—C3—H3A	120.3	C11—C12—H12A	120.0
C2—C3—H3A	120.3	C12—C13—C8	120.8 (5)
C3—C4—C5	121.3 (5)	C12—C13—H13A	119.6
C3—C4—H4A	119.4	C8—C13—H13A	119.6
C5—C4—H4A	119.4	N1—C14—H14A	106.9
N1—C5—C6	122.4 (5)	N1—C14—H14B	112.4
N1—C5—C4	116.8 (5)	H14A—C14—H14B	111.7
C6—C5—C4	120.8 (5)	N2—C15—H15A	107.3
C7—C6—C5	127.2 (5)	N2—C15—H15B	111.7
C7—C6—H6A	116.4	H15A—C15—H15B	111.7
C5—C6—H6A	116.4	N2—C16—H16A	107.2
C6—C7—C8	129.3 (5)	N2—C16—H16B	111.9
C6—C7—H7A	115.4	H16A—C16—H16B	111.7

C5—N1—C1—C2	0.000 (3)	C6—C7—C8—C13	0.000 (2)
C14—N1—C1—C2	180.000 (2)	C13—C8—C9—C10	0.000 (2)
N1—C1—C2—C3	0.000 (3)	C7—C8—C9—C10	180.000 (2)
C1—C2—C3—C4	0.000 (3)	C8—C9—C10—C11	0.000 (2)
C2—C3—C4—C5	0.000 (3)	C15—N2—C11—C10	0.000 (2)
C1—N1—C5—C6	180.000 (2)	C16—N2—C11—C10	180.000 (1)
C14—N1—C5—C6	0.000 (3)	C15—N2—C11—C12	180.000 (1)
C1—N1—C5—C4	0.000 (3)	C16—N2—C11—C12	0.000 (2)
C14—N1—C5—C4	180.000 (2)	C9—C10—C11—N2	180.000 (1)
C3—C4—C5—N1	0.000 (2)	C9—C10—C11—C12	0.000 (2)
C3—C4—C5—C6	180.000 (2)	N2—C11—C12—C13	180.000 (2)
N1—C5—C6—C7	180.000 (2)	C10—C11—C12—C13	0.000 (2)
C4—C5—C6—C7	0.000 (3)	C11—C12—C13—C8	0.000 (2)
C5—C6—C7—C8	180.000 (2)	C9—C8—C13—C12	0.000 (2)
C6—C7—C8—C9	180.000 (2)	C7—C8—C13—C12	180.000 (2)

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

Experimental details

Crystal data
Chemical formula	C₁₆H₁₉N₂⁺·I₃⁻
M_r	620.03
Crystal system, space group	Monoclinic, C2/m
Temperature (K)	100
a, b, c (Å)	19.8760 (3), 6.6126 (1), 14.4421 (2)
β (°)	95.107 (1)
V (Å³)	1890.62 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	4.96
Crystal size (mm)	0.45 × 0.15 × 0.04

Data collection
Diffractometer	Bruker APEX DUO CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2009)
T_min, T_max	0.212, 0.838
No. of measured, independent and observed [I > 2σ(I)] reflections	16143, 2484, 2263
R_int	0.030
(sin θ/λ)_max (Å⁻¹)	0.661

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.030, 0.079, 1.04
No. of reflections	2484
No. of parameters	129
H-atom treatment	H-atom parameters constrained
	w = 1/[σ²(F_o²) + (0.0387P)² + 13.6577P] where P = (F_o² + 2F_c²)/3
Δρ_max, Δρ_min (e Å⁻³)	1.74, −0.60

Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Footnotes

‡Thomson Reuters ResearcherID: A-3561-2009.

§Additional correspondence author, email: suchada.c@psu.ac.th. Thomson Reuters ResearcherID: A-5085-2009.

Acknowledgements

Financial support by the Prince of Songkla University is greatfully acknowledged. The authors also thank Universiti Sains Malaysia for the Research University Grant No. 1001/PFIZIK/811160. KC thanks the Crystal Materials Research Unit for the Research Assistance fellowship.

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
Bruker (2009). APEX2, SAINT and SADABS, Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Chanawanno, K., Chantrapromma, S., Anantapong, T., Kanjana-Opas, A. & Fun, H.-K. (2010). Eur. J. Med. Chem. 45, 4199–4208. Web of Science CSD CrossRef CAS PubMed Google Scholar
Chantrapromma, S., Chanawanno, K. & Fun, H.-K. (2010). Acta Cryst. E66, o1975–o1976. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Cosier, J. & Glazer, A. M. (1986). J. Appl. Cryst. 19, 105–107. CrossRef CAS Web of Science IUCr Journals Google Scholar
Fisicaro, E., Pelizzetti, E., Barbieri, M., Savarino, P. & Viscardi, G. (1990). Thermochim. Acta, 168, 143–159. CrossRef CAS Web of Science Google Scholar
Pernak, J., Kalewska, J., Ksycifiska, H. & Cybulski, J. (2001). Eur. J. Med. Chem. 36, 899–907. Web of Science CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Zhang, X. H., Wang, L. Y., Zhai, G. H., Wen, Z. Y. & Zhang, Z. X. (2008). J. Mol. Struct. 881, 117–122. Web of Science CSD CrossRef CAS Google Scholar