2-Ethyl-5-triphenyl­methyl-1,3-dioxane

Yuan, L.; Shi, J.-H.; Zhang, M.; Ng, S.W.

doi:10.1107/S1600536810036767

organic compounds

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ISSN: 2056-9890

Volume 66| Part 10| October 2010| Page o2582

doi:10.1107/S1600536810036767

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2-Ethyl-5-triphenylmethyl-1,3-dioxane

Lin Yuan,^a Jiang-Hua Shi,^a Min Zhang ^a and Seik Weng Ng ^b ^*

^aDepartment of Biology and Chemistry, Hunan University of Science and Engineering, Yongzhou Hunan 425100, People's Republic of China, and ^bDepartment of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia
^*Correspondence e-mail: seikweng@um.edu.my

(Received 9 September 2010; accepted 14 September 2010; online 18 September 2010)

In the title compound, C₂₅H₂₆O₂, the dioxane ring adopts a chair conformation with the two substituent groups occupying equatorial positions.

Related literature

For the crystal structure of 2,2-dimethyl-5-triphenyl-1,3-dioxane, see: Zhang et al. (2009 ).

Experimental

Crystal data

C₂₅H₂₆O₂
M_r = 358.46
Monoclinic, P 2₁ /c
a = 10.5401 (6) Å
b = 13.3550 (8) Å
c = 14.6044 (8) Å
β = 110.523 (1)°
V = 1925.28 (19) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 110 K
0.45 × 0.35 × 0.15 mm

Data collection

Bruker SMART APEX diffractometer
9493 measured reflections
4174 independent reflections
3047 reflections with I > 2σ(I)
R_int = 0.031

Refinement

R[F² > 2σ(F²)] = 0.042
wR(F²) = 0.114
S = 1.04
4174 reflections
244 parameters
H-atom parameters constrained
Δρ_max = 0.29 e Å⁻³
Δρ_min = −0.19 e Å⁻³

Data collection: SMART (Bruker, 2003 ); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001 ); software used to prepare material for publication: publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810036767/zs2066sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536810036767/zs2066Isup2.hkl

checkCIF report

Comment top

A previous study reported the crystal structure of 2,2-dimethyl-5-triphenylmethyl-1,3-dioxane (Zhang et al., 2009). Such disubstituted 1,3-dioxanes are known from NMR studies to have substituents in equatorial rather than in axial orientations on the six-membered ring. The the title compound, 2-ethyl-5-triphenylmethyl-1,3-dioxane analog (Scheme I, Fig. 1), has similar features for the dioxane part, which adopts a chair conformation. The substitutent groups occupy equatorial positions.

Related literature top

For the crystal structure of 2,2-dimethyl-5-triphenyl-1,3-dioxane, see: Zhang et al. (2009).

Experimental top

2-Triphenylmethyl-1,3-propanediol (0.24 g, 5.0 mmol), propionaldehyde (20 mmol) and p-toluenesulfonic acid (0.1 g) were stirred in dichloromethane (20 ml) for a week. The solvent was evaporated and the residue was dissolved in ether (20 ml) after which the solution was washed with water and 5% sodium bicarbonate (20 ml). The organic phase was dried with anhydrous sodium sulfate. The solvent was evaporated and the product was recrystallized from ethyl acetate to give 1.0 g (yield 60%) of colorless crystals.

Computing details top

Data collection: SMART (Bruker, 2003); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT (Bruker, 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top

Fig. 1. Thermal ellipsoid plot (Barbour, 2001) of the title compound at the 70% probability level.

2-Ethyl-5-triphenylmethyl-1,3-dioxane top

Crystal data top

C₂₅H₂₆O₂	F(000) = 768
M_r = 358.46	D_x = 1.237 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3994 reflections
a = 10.5401 (6) Å	θ = 2.6–27.0°
b = 13.3550 (8) Å	µ = 0.08 mm⁻¹
c = 14.6044 (8) Å	T = 110 K
β = 110.523 (1)°	Block, colorless
V = 1925.28 (19) Å³	0.45 × 0.35 × 0.15 mm
Z = 4

Data collection top

Bruker SMART APEX diffractometer	3047 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.031
Graphite monochromator	θ_max = 27.1°, θ_min = 2.1°
ω scans	h = −9→13
9493 measured reflections	k = −17→12
4174 independent reflections	l = −18→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)] = 0.042	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.114	H-atom parameters constrained
S = 1.04	w = 1/[σ²(F_o²) + (0.0568P)² + 0.2859P] where P = (F_o² + 2F_c²)/3
4174 reflections	(Δ/σ)_max = 0.001
244 parameters	Δρ_max = 0.29 e Å⁻³
0 restraints	Δρ_min = −0.19 e Å⁻³

Crystal data top

C₂₅H₂₆O₂	V = 1925.28 (19) Å³
M_r = 358.46	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 10.5401 (6) Å	µ = 0.08 mm⁻¹
b = 13.3550 (8) Å	T = 110 K
c = 14.6044 (8) Å	0.45 × 0.35 × 0.15 mm
β = 110.523 (1)°

Data collection top

Bruker SMART APEX diffractometer	3047 reflections with I > 2σ(I)
9493 measured reflections	R_int = 0.031
4174 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.042	0 restraints
wR(F²) = 0.114	H-atom parameters constrained
S = 1.04	Δρ_max = 0.29 e Å⁻³
4174 reflections	Δρ_min = −0.19 e Å⁻³
244 parameters

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

	x	y	z	U_iso*/U_eq
O1	0.30810 (9)	0.32447 (7)	0.08575 (6)	0.0188 (2)
O2	0.26796 (9)	0.32596 (7)	0.23220 (7)	0.0191 (2)
C1	0.71880 (14)	0.43893 (10)	0.23149 (9)	0.0179 (3)
C2	0.65864 (15)	0.52062 (11)	0.17152 (10)	0.0212 (3)
H2	0.5682	0.5389	0.1633	0.025*
C3	0.72914 (16)	0.57512 (11)	0.12403 (11)	0.0258 (3)
H3	0.6864	0.6300	0.0835	0.031*
C4	0.86148 (16)	0.55018 (12)	0.13528 (11)	0.0272 (4)
H4	0.9093	0.5872	0.1022	0.033*
C5	0.92283 (15)	0.47091 (12)	0.19517 (11)	0.0249 (3)
H5	1.0137	0.4537	0.2038	0.030*
C6	0.85276 (14)	0.41622 (11)	0.24288 (10)	0.0214 (3)
H6	0.8968	0.3622	0.2841	0.026*
C7	0.69636 (13)	0.27847 (10)	0.32337 (10)	0.0196 (3)
C8	0.72962 (14)	0.21427 (11)	0.25990 (11)	0.0242 (3)
H8	0.7284	0.2387	0.1985	0.029*
C9	0.76470 (15)	0.11462 (12)	0.28526 (13)	0.0325 (4)
H9	0.7870	0.0719	0.2411	0.039*
C10	0.76718 (16)	0.07774 (12)	0.37422 (14)	0.0361 (4)
H10	0.7914	0.0100	0.3915	0.043*
C11	0.73423 (16)	0.13999 (12)	0.43758 (13)	0.0316 (4)
H11	0.7355	0.1150	0.4988	0.038*
C12	0.69899 (14)	0.23933 (11)	0.41254 (11)	0.0239 (3)
H12	0.6763	0.2813	0.4570	0.029*
C13	0.67391 (13)	0.45454 (10)	0.38294 (9)	0.0161 (3)
C14	0.80413 (14)	0.45411 (11)	0.45377 (10)	0.0194 (3)
H14	0.8701	0.4091	0.4470	0.023*
C15	0.83889 (15)	0.51776 (11)	0.53341 (10)	0.0226 (3)
H15	0.9278	0.5156	0.5807	0.027*
C16	0.74504 (15)	0.58467 (11)	0.54476 (10)	0.0214 (3)
H16	0.7689	0.6287	0.5993	0.026*
C17	0.61592 (15)	0.58622 (11)	0.47519 (10)	0.0202 (3)
H17	0.5504	0.6314	0.4824	0.024*
C18	0.58085 (14)	0.52241 (10)	0.39474 (10)	0.0183 (3)
H18	0.4921	0.5253	0.3473	0.022*
C19	0.64436 (13)	0.38587 (10)	0.29220 (9)	0.0162 (3)
C20	0.48869 (13)	0.37838 (10)	0.23326 (9)	0.0163 (3)
H20	0.4528	0.4483	0.2205	0.020*
C21	0.45229 (13)	0.32618 (11)	0.13438 (10)	0.0191 (3)
H21A	0.4950	0.3620	0.0933	0.023*
H21B	0.4876	0.2568	0.1440	0.023*
C22	0.41008 (13)	0.32455 (11)	0.28894 (10)	0.0186 (3)
H22A	0.4418	0.2545	0.3020	0.022*
H22B	0.4263	0.3582	0.3525	0.022*
C23	0.24357 (14)	0.27454 (11)	0.14269 (9)	0.0178 (3)
H23A	0.2791	0.2046	0.1563	0.021*
C24	0.09327 (14)	0.27184 (11)	0.08743 (10)	0.0207 (3)
H24A	0.0758	0.2405	0.0227	0.025*
H24B	0.0578	0.3412	0.0765	0.025*
C25	0.01923 (15)	0.21322 (12)	0.14283 (11)	0.0261 (3)
H25A	−0.0782	0.2131	0.1051	0.039*
H25B	0.0354	0.2447	0.2066	0.039*
H25C	0.0528	0.1442	0.1525	0.039*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0172 (5)	0.0204 (5)	0.0174 (5)	−0.0028 (4)	0.0042 (4)	−0.0008 (4)
O2	0.0159 (5)	0.0221 (5)	0.0181 (5)	−0.0013 (4)	0.0044 (4)	−0.0033 (4)
C1	0.0206 (7)	0.0169 (7)	0.0162 (6)	−0.0041 (6)	0.0063 (6)	−0.0047 (5)
C2	0.0219 (7)	0.0204 (7)	0.0207 (7)	−0.0027 (6)	0.0068 (6)	−0.0014 (6)
C3	0.0340 (9)	0.0213 (8)	0.0204 (7)	−0.0075 (7)	0.0076 (6)	0.0004 (6)
C4	0.0339 (9)	0.0294 (9)	0.0226 (7)	−0.0150 (7)	0.0152 (7)	−0.0060 (6)
C5	0.0219 (8)	0.0283 (8)	0.0267 (8)	−0.0083 (6)	0.0113 (6)	−0.0099 (6)
C6	0.0224 (7)	0.0198 (7)	0.0218 (7)	−0.0034 (6)	0.0076 (6)	−0.0056 (6)
C7	0.0137 (7)	0.0143 (7)	0.0275 (7)	−0.0004 (5)	0.0031 (6)	−0.0001 (6)
C8	0.0158 (7)	0.0200 (7)	0.0330 (8)	−0.0008 (6)	0.0039 (6)	−0.0045 (6)
C9	0.0188 (8)	0.0197 (8)	0.0509 (11)	0.0021 (6)	0.0019 (7)	−0.0099 (7)
C10	0.0217 (8)	0.0151 (8)	0.0569 (11)	0.0009 (6)	−0.0045 (8)	0.0038 (8)
C11	0.0225 (8)	0.0232 (8)	0.0393 (9)	−0.0026 (7)	−0.0016 (7)	0.0110 (7)
C12	0.0196 (7)	0.0192 (7)	0.0287 (8)	−0.0020 (6)	0.0034 (6)	0.0038 (6)
C13	0.0191 (7)	0.0122 (7)	0.0176 (6)	−0.0023 (5)	0.0072 (5)	0.0021 (5)
C14	0.0175 (7)	0.0193 (7)	0.0218 (7)	0.0001 (6)	0.0074 (6)	0.0014 (6)
C15	0.0197 (7)	0.0250 (8)	0.0208 (7)	−0.0045 (6)	0.0042 (6)	0.0001 (6)
C16	0.0278 (8)	0.0189 (7)	0.0187 (7)	−0.0053 (6)	0.0096 (6)	−0.0028 (6)
C17	0.0252 (8)	0.0160 (7)	0.0213 (7)	0.0012 (6)	0.0106 (6)	0.0028 (6)
C18	0.0190 (7)	0.0168 (7)	0.0182 (7)	−0.0001 (6)	0.0053 (5)	0.0024 (5)
C19	0.0160 (7)	0.0139 (7)	0.0178 (7)	0.0002 (5)	0.0047 (5)	0.0006 (5)
C20	0.0158 (7)	0.0152 (7)	0.0166 (7)	0.0005 (5)	0.0042 (5)	−0.0003 (5)
C21	0.0165 (7)	0.0203 (7)	0.0200 (7)	−0.0014 (6)	0.0059 (6)	−0.0020 (6)
C22	0.0151 (7)	0.0217 (7)	0.0175 (7)	−0.0013 (6)	0.0039 (5)	0.0006 (6)
C23	0.0200 (7)	0.0150 (7)	0.0185 (7)	−0.0011 (6)	0.0067 (6)	−0.0012 (5)
C24	0.0198 (7)	0.0196 (7)	0.0204 (7)	−0.0001 (6)	0.0042 (6)	−0.0022 (6)
C25	0.0193 (7)	0.0286 (8)	0.0286 (8)	−0.0044 (6)	0.0064 (6)	−0.0006 (7)

Geometric parameters (Å, º) top

O1—C23	1.4125 (16)	C13—C18	1.3899 (19)
O1—C21	1.4345 (15)	C13—C14	1.3994 (19)
O2—C23	1.4181 (15)	C13—C19	1.5509 (18)
O2—C22	1.4355 (15)	C14—C15	1.382 (2)
C1—C6	1.3959 (19)	C14—H14	0.9500
C1—C2	1.403 (2)	C15—C16	1.385 (2)
C1—C19	1.5465 (19)	C15—H15	0.9500
C2—C3	1.387 (2)	C16—C17	1.384 (2)
C2—H2	0.9500	C16—H16	0.9500
C3—C4	1.387 (2)	C17—C18	1.3925 (19)
C3—H3	0.9500	C17—H17	0.9500
C4—C5	1.381 (2)	C18—H18	0.9500
C4—H4	0.9500	C19—C20	1.5661 (18)
C5—C6	1.387 (2)	C20—C21	1.5264 (18)
C5—H5	0.9500	C20—C22	1.5287 (19)
C6—H6	0.9500	C20—H20	1.0000
C7—C8	1.395 (2)	C21—H21A	0.9900
C7—C12	1.395 (2)	C21—H21B	0.9900
C7—C19	1.5459 (19)	C22—H22A	0.9900
C8—C9	1.396 (2)	C22—H22B	0.9900
C8—H8	0.9500	C23—C24	1.5053 (18)
C9—C10	1.381 (3)	C23—H23A	1.0000
C9—H9	0.9500	C24—C25	1.523 (2)
C10—C11	1.376 (2)	C24—H24A	0.9900
C10—H10	0.9500	C24—H24B	0.9900
C11—C12	1.392 (2)	C25—H25A	0.9800
C11—H11	0.9500	C25—H25B	0.9800
C12—H12	0.9500	C25—H25C	0.9800

C23—O1—C21	111.18 (10)	C15—C16—H16	120.6
C23—O2—C22	109.94 (10)	C16—C17—C18	120.80 (13)
C6—C1—C2	117.39 (13)	C16—C17—H17	119.6
C6—C1—C19	121.83 (12)	C18—C17—H17	119.6
C2—C1—C19	120.33 (12)	C13—C18—C17	120.90 (13)
C3—C2—C1	121.06 (14)	C13—C18—H18	119.6
C3—C2—H2	119.5	C17—C18—H18	119.6
C1—C2—H2	119.5	C7—C19—C1	113.28 (11)
C4—C3—C2	120.50 (14)	C7—C19—C13	110.66 (11)
C4—C3—H3	119.7	C1—C19—C13	103.22 (10)
C2—C3—H3	119.7	C7—C19—C20	107.31 (11)
C5—C4—C3	119.17 (14)	C1—C19—C20	111.01 (10)
C5—C4—H4	120.4	C13—C19—C20	111.43 (11)
C3—C4—H4	120.4	C21—C20—C22	106.57 (11)
C4—C5—C6	120.53 (14)	C21—C20—C19	114.62 (11)
C4—C5—H5	119.7	C22—C20—C19	113.35 (10)
C6—C5—H5	119.7	C21—C20—H20	107.3
C5—C6—C1	121.34 (14)	C22—C20—H20	107.3
C5—C6—H6	119.3	C19—C20—H20	107.3
C1—C6—H6	119.3	O1—C21—C20	110.30 (11)
C8—C7—C12	117.57 (14)	O1—C21—H21A	109.6
C8—C7—C19	121.37 (13)	C20—C21—H21A	109.6
C12—C7—C19	120.78 (13)	O1—C21—H21B	109.6
C7—C8—C9	120.98 (15)	C20—C21—H21B	109.6
C7—C8—H8	119.5	H21A—C21—H21B	108.1
C9—C8—H8	119.5	O2—C22—C20	109.71 (10)
C10—C9—C8	120.36 (16)	O2—C22—H22A	109.7
C10—C9—H9	119.8	C20—C22—H22A	109.7
C8—C9—H9	119.8	O2—C22—H22B	109.7
C11—C10—C9	119.42 (15)	C20—C22—H22B	109.7
C11—C10—H10	120.3	H22A—C22—H22B	108.2
C9—C10—H10	120.3	O1—C23—O2	110.18 (10)
C10—C11—C12	120.42 (16)	O1—C23—C24	109.22 (11)
C10—C11—H11	119.8	O2—C23—C24	108.81 (11)
C12—C11—H11	119.8	O1—C23—H23A	109.5
C11—C12—C7	121.26 (15)	O2—C23—H23A	109.5
C11—C12—H12	119.4	C24—C23—H23A	109.5
C7—C12—H12	119.4	C23—C24—C25	111.50 (11)
C18—C13—C14	117.58 (12)	C23—C24—H24A	109.3
C18—C13—C19	123.54 (12)	C25—C24—H24A	109.3
C14—C13—C19	118.71 (12)	C23—C24—H24B	109.3
C15—C14—C13	121.43 (13)	C25—C24—H24B	109.3
C15—C14—H14	119.3	H24A—C24—H24B	108.0
C13—C14—H14	119.3	C24—C25—H25A	109.5
C14—C15—C16	120.50 (13)	C24—C25—H25B	109.5
C14—C15—H15	119.8	H25A—C25—H25B	109.5
C16—C15—H15	119.8	C24—C25—H25C	109.5
C17—C16—C15	118.78 (13)	H25A—C25—H25C	109.5
C17—C16—H16	120.6	H25B—C25—H25C	109.5

C6—C1—C2—C3	1.3 (2)	C6—C1—C19—C7	−28.71 (17)
C19—C1—C2—C3	173.68 (12)	C2—C1—C19—C7	159.22 (12)
C1—C2—C3—C4	−0.3 (2)	C6—C1—C19—C13	91.00 (14)
C2—C3—C4—C5	−0.6 (2)	C2—C1—C19—C13	−81.08 (14)
C3—C4—C5—C6	0.6 (2)	C6—C1—C19—C20	−149.52 (12)
C4—C5—C6—C1	0.4 (2)	C2—C1—C19—C20	38.41 (16)
C2—C1—C6—C5	−1.3 (2)	C18—C13—C19—C7	−136.57 (13)
C19—C1—C6—C5	−173.61 (12)	C14—C13—C19—C7	48.34 (16)
C12—C7—C8—C9	−0.2 (2)	C18—C13—C19—C1	101.94 (14)
C19—C7—C8—C9	−174.13 (13)	C14—C13—C19—C1	−73.15 (14)
C7—C8—C9—C10	−0.1 (2)	C18—C13—C19—C20	−17.26 (17)
C8—C9—C10—C11	0.3 (2)	C14—C13—C19—C20	167.65 (12)
C9—C10—C11—C12	−0.2 (2)	C7—C19—C20—C21	−68.12 (14)
C10—C11—C12—C7	−0.2 (2)	C1—C19—C20—C21	56.15 (15)
C8—C7—C12—C11	0.4 (2)	C13—C19—C20—C21	170.60 (11)
C19—C7—C12—C11	174.28 (13)	C7—C19—C20—C22	54.53 (14)
C18—C13—C14—C15	0.9 (2)	C1—C19—C20—C22	178.81 (11)
C19—C13—C14—C15	176.25 (12)	C13—C19—C20—C22	−66.75 (14)
C13—C14—C15—C16	−0.5 (2)	C23—O1—C21—C20	−58.77 (14)
C14—C15—C16—C17	0.3 (2)	C22—C20—C21—O1	54.60 (14)
C15—C16—C17—C18	−0.5 (2)	C19—C20—C21—O1	−179.15 (10)
C14—C13—C18—C17	−1.1 (2)	C23—O2—C22—C20	61.61 (14)
C19—C13—C18—C17	−176.24 (12)	C21—C20—C22—O2	−56.23 (14)
C16—C17—C18—C13	0.9 (2)	C19—C20—C22—O2	176.77 (10)
C8—C7—C19—C1	−39.96 (17)	C21—O1—C23—O2	62.29 (13)
C12—C7—C19—C1	146.35 (12)	C21—O1—C23—C24	−178.24 (11)
C8—C7—C19—C13	−155.31 (12)	C22—O2—C23—O1	−63.62 (13)
C12—C7—C19—C13	31.00 (17)	C22—O2—C23—C24	176.67 (11)
C8—C7—C19—C20	82.92 (15)	O1—C23—C24—C25	176.55 (12)
C12—C7—C19—C20	−90.77 (15)	O2—C23—C24—C25	−63.14 (15)

Experimental details

Crystal data
Chemical formula	C₂₅H₂₆O₂
M_r	358.46
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	110
a, b, c (Å)	10.5401 (6), 13.3550 (8), 14.6044 (8)
β (°)	110.523 (1)
V (Å³)	1925.28 (19)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.08
Crystal size (mm)	0.45 × 0.35 × 0.15

Data collection
Diffractometer	Bruker SMART APEX diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	9493, 4174, 3047
R_int	0.031
(sin θ/λ)_max (Å⁻¹)	0.640

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.042, 0.114, 1.04
No. of reflections	4174
No. of parameters	244
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.29, −0.19

Computer programs: SMART (Bruker, 2003), SAINT (Bruker, 2003), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), X-SEED (Barbour, 2001), publCIF (Westrip, 2010).

Acknowledgements

We thank the Key Subject Construction Project of Hunan Province (No. 2006–180), the Key Scientific Research Project of Hunan Provincial Education Department (No. 08 A023, 05 C736), the NSF of Hunan Province (09 J J3028) and the University of Malaya for supporting this study.

References

Barbour, L. J. (2001). J. Supramol. Chem. 1, 189–191. CrossRef CAS Google Scholar
Bruker (2003). SAINT and SMART. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar
Zhang, M., Yuan, X.-Y. & Liu, X.-M. (2009). Acta Cryst. E65, o304. Web of Science CSD CrossRef IUCr Journals Google Scholar