6-Chloro-1-(3,5-dimethyl­phenyl­sulfon­yl)-1H-benzimidazol-2(3H)-one

Meneghetti, F.; Bombieri, G.; Logoteta, P.; De Luca, L.

doi:10.1107/S1600536808042694

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 65| Part 1| January 2009| Page o159

doi:10.1107/S1600536808042694

Open

access

6-Chloro-1-(3,5-dimethylphenylsulfonyl)-1H-benzimidazol-2(3H)-one

Fiorella Meneghetti,^a ^* Gabriella Bombieri,^a Patrizia Logoteta ^b and Laura De Luca ^b

^aInstitute of Pharmaceutical and Toxicological Chemistry, "P. Pratesi", University of Milano, via L. Mangiagalli, 25, 20133-Milano, Italy, and ^bDepartment of Pharmaceutical Chemistry, University of Messina, viale Annunziata, 98168-Messina, Italy
^*Correspondence e-mail: fiorella.meneghetti@unimi.it

(Received 28 November 2008; accepted 15 December 2008; online 20 December 2008)

The title compound, C₁₅H₁₃ClN₂O₃S, is one of a series of N¹-benzyl-1,3-dihydro-2H-benzimidazol-2-one derivatives, a new class of non-nucleoside HIV-1 reverse transcriptase inhibitors. The dihedral angle between the two pharmacophoric groups, the dimethylbenzene ring and the benzimidazolone ring system, is 88 (1)°, giving a butterfly-like conformation to the molecule. The molecular packing is characterized by a bifurcated N—H⋯(O,O) hydrogen bond and short Cl⋯O contacts of 3.122 (2) Å. In addition, π–π stacking of the benzimidazolone rings is also present, with interplanar separations of 3.95 (1) Å.

Related literature

For the role of the substituents on the benzene nucleus in anti-HIV-1 compounds, see: Barreca et al. (2007 ). For related literature, see: Barreca et al. (2005 ); Beddoes et al. (1986 ); Liu et al. (2007 ).

Experimental

Crystal data

C₁₅H₁₃ClN₂O₃S
M_r = 336.78
Monoclinic, P 2₁ /c
a = 12.173 (3) Å
b = 14.036 (3) Å
c = 8.949 (2) Å
β = 95.77 (2)°
V = 1521.3 (6) Å³
Z = 4
Mo Kα radiation
μ = 0.40 mm⁻¹
T = 293 (2) K
0.5 × 0.4 × 0.3 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
Absorption correction: none
3964 measured reflections
3634 independent reflections
3214 reflections with I > 2σ(I)
R_int = 0.014
3 standard reflections frequency: 120 min intensity decay: 1%

Refinement

R[F² > 2σ(F²)] = 0.057
wR(F²) = 0.133
S = 1.19
3634 reflections
199 parameters
H-atom parameters constrained
Δρ_max = 0.23 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2⋯O1ⁱ	0.86	2.18	2.852 (3)	135
N2—H2⋯O2ⁱ	0.86	2.39	3.075 (3)	138
Symmetry code: (i) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ .

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: SIR92 (Altomare et al., 1994 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808042694/fj2178sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808042694/fj2178Isup2.hkl

checkCIF report

Comment top

In the course of previous studies on new anti-HIV agents, some of us reported the synthesis and anti-HIV activity of a series of N1-benzyl-1,3-dihydro-2H-benzimidazol-2-ones, a new class of non-nucleoside HIV-1 reverse transcriptase inhibitors (NNRTIs) (Barreca et al. 2005). More recently molecular modeling studies led to the discovery of N1-phenylsulfonyl-1,3-dihydro-2H-benzimidazol-2-ones as highly potent NNRTIs active at nanomolar concentration (Barreca et al. 2007). In this paper we report the results of the X-ray structure determination of 6-chloro-1-(3,5-dimethylphenylsulfonyl)-1,3-dihydro-2H-benzimidazol-2-one (I) the most potent derivative of the series, active against wild-type and mutant HIV-1 strains (Barreca et al., 2007). On this respect, its geometrical features defined by X-ray analysis (Fig. 1), could be an useful tool to understand the structure-activity relationship of this class of compounds. The bicyclic part of the molecule consists of an aromatic ring (C2 to C7) and an imidazol-2(3H)-one nucleus approximately planar. This bicyclic fragment makes a dihedral angle of 88 (1)° with the dimethylphenyl ring. Such geometry is in agreement with the best docked conformation previously calculated (Barreca et al., 2007) and match well with the pharmacophoric model proposed for the interactions with the macromolecule. As previously observed in other N-(phenylsulfonyl)indoles (Liu et al., 2007) and N-phenylsulfonamides, (Beddoes et al., 1986) the N atom lone pair eclipses the sulfonyl group; accordingly the corresponding torsion angle O(2)—S(1)—N(1)—C(7) is 48.4 (2)°. In the crystal packing are present two intermolecular hydrogen bonds (Fig. 2) between N2—H2 and O1^I at a distance of 2.18 (2) Å, angle 134.2 (2)° and N2—H2 with O2^I of 2.39 (2) Å, angle 137.9 (4)°, forming a biforcated linkage with the adjacent molecule at x; 1/2 - y; z + 1/2. The crystal structure is also stabilized by π-π stacking of the benzimidazolone moieties [3.95 (1) Å] and by short intermolecular Cl(1)···O(3)^I contacts [3.122 (2) Å].

Related literature top

For the role of the substituents on the benzene nucleus in anti-HIV-1 compounds, see: Barreca et al. (2007). For related literature, see: Barreca et al. (2005); Beddoes et al. (1986); Liu et al. (2007).

Experimental top

The compound I has been synthesized as previously reported (Barreca et al., 2007). Single crystals were obtained at room temperature by slow evaporation of a CHCl₃ solution.

Computing details top

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: SHELXL97 (Sheldrick, 2008); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top

	Fig. 1. : The molecular structure of the title compound, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 40% probability level.
	Fig. 2. : Packing diagram of the title compound, showing the intermolecular interactions as dotted lines.

6-Chloro-1-(3,5-dimethylphenylsulfonyl)-1H-benzimidazol-2(3H)-one top

Crystal data top

C₁₅H₁₃ClN₂O₃S	F(000) = 696
M_r = 336.78	D_x = 1.470 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 25 reflections
a = 12.173 (3) Å	θ = 9–10°
b = 14.036 (3) Å	µ = 0.40 mm⁻¹
c = 8.949 (2) Å	T = 293 K
β = 95.77 (2)°	Prism, colourless
V = 1521.3 (6) Å³	0.5 × 0.4 × 0.3 mm
Z = 4

Data collection top

Enraf–Nonius CAD-4 diffractometer	R_int = 0.014
Radiation source: fine-focus sealed tube	θ_max = 28.0°, θ_min = 3.3°
Graphite monochromator	h = −16→15
Non–profiled ω/2θ scans	k = 0→18
3964 measured reflections	l = 0→11
3634 independent reflections	3 standard reflections every 120 min
3214 reflections with I > 2σ(I)	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)] = 0.057	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.133	H-atom parameters constrained
S = 1.19	w = 1/[σ²(F_o²) + (0.0188P)² + 1.7615P] where P = (F_o² + 2F_c²)/3
3634 reflections	(Δ/σ)_max = 0.003
199 parameters	Δρ_max = 0.23 e Å⁻³
0 restraints	Δρ_min = −0.27 e Å⁻³

Crystal data top

C₁₅H₁₃ClN₂O₃S	V = 1521.3 (6) Å³
M_r = 336.78	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 12.173 (3) Å	µ = 0.40 mm⁻¹
b = 14.036 (3) Å	T = 293 K
c = 8.949 (2) Å	0.5 × 0.4 × 0.3 mm
β = 95.77 (2)°

Data collection top

Enraf–Nonius CAD-4 diffractometer	R_int = 0.014
3964 measured reflections	3 standard reflections every 120 min
3634 independent reflections	intensity decay: 1%
3214 reflections with I > 2σ(I)

Refinement top

R[F² > 2σ(F²)] = 0.057	0 restraints
wR(F²) = 0.133	H-atom parameters constrained
S = 1.19	Δρ_max = 0.23 e Å⁻³
3634 reflections	Δρ_min = −0.27 e Å⁻³
199 parameters

Special details top

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
S1	0.78957 (6)	0.45343 (4)	0.18441 (6)	0.04124 (17)
Cl1	0.89540 (9)	0.73749 (6)	0.67132 (11)	0.0776 (3)
O3	0.81132 (18)	0.55252 (13)	0.1756 (2)	0.0524 (5)
O1	0.80048 (19)	0.25911 (13)	0.3298 (2)	0.0545 (5)
N2	0.85398 (19)	0.32965 (15)	0.5597 (2)	0.0426 (5)
H2	0.8602	0.2802	0.6166	0.051*
N1	0.83211 (18)	0.42285 (14)	0.3607 (2)	0.0371 (4)
O2	0.83888 (19)	0.38810 (15)	0.0896 (2)	0.0567 (5)
C2	0.8705 (2)	0.42257 (18)	0.6105 (3)	0.0387 (5)
C8	0.6470 (2)	0.4341 (2)	0.1704 (3)	0.0508 (6)
C7	0.85543 (19)	0.48366 (17)	0.4866 (2)	0.0351 (5)
C1	0.8269 (2)	0.32671 (17)	0.4093 (3)	0.0417 (5)
C4	0.9024 (2)	0.5555 (2)	0.7717 (3)	0.0519 (7)
H4	0.9177	0.5817	0.8670	0.062*
C6	0.8637 (2)	0.58080 (18)	0.5011 (3)	0.0425 (5)
H6	0.8547	0.6215	0.4188	0.051*
C3	0.8955 (2)	0.4574 (2)	0.7537 (3)	0.0464 (6)
H3	0.9074	0.4166	0.8356	0.056*
C5	0.8864 (2)	0.61419 (19)	0.6469 (3)	0.0491 (6)
C13	0.6006 (3)	0.3614 (3)	0.0822 (4)	0.0734 (10)
H13	0.6452	0.3204	0.0334	0.088*
C9	0.5842 (3)	0.4951 (3)	0.2471 (4)	0.0671 (9)
H9	0.6174	0.5437	0.3060	0.081*
C11	0.4255 (4)	0.4091 (4)	0.1443 (5)	0.0941 (15)
H11	0.3495	0.3998	0.1362	0.113*
C10	0.4705 (3)	0.4829 (4)	0.2352 (5)	0.0858 (12)
C12	0.4884 (4)	0.3499 (3)	0.0666 (6)	0.0954 (15)
C15	0.4332 (5)	0.2721 (4)	−0.0324 (8)	0.152 (2)
H15A	0.3928	0.2305	0.0274	0.229*
H15B	0.4884	0.2362	−0.0772	0.229*
H15C	0.3835	0.3005	−0.1099	0.229*
C14	0.4004 (4)	0.5506 (5)	0.3165 (7)	0.1339 (17)
H14A	0.4464	0.5843	0.3924	0.201*
H14B	0.3454	0.5152	0.3626	0.201*
H14C	0.3650	0.5953	0.2462	0.201*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S1	0.0549 (4)	0.0401 (3)	0.0290 (3)	0.0002 (3)	0.0055 (2)	0.0037 (2)
Cl1	0.1068 (7)	0.0451 (4)	0.0801 (6)	−0.0057 (4)	0.0058 (5)	−0.0229 (4)
O3	0.0702 (13)	0.0436 (10)	0.0431 (10)	−0.0050 (9)	0.0043 (9)	0.0112 (8)
O1	0.0876 (15)	0.0359 (9)	0.0394 (10)	−0.0034 (9)	0.0039 (9)	−0.0019 (8)
N2	0.0592 (13)	0.0362 (10)	0.0325 (10)	0.0004 (9)	0.0044 (9)	0.0061 (8)
N1	0.0522 (12)	0.0326 (9)	0.0266 (9)	0.0025 (8)	0.0046 (8)	0.0029 (7)
O2	0.0803 (14)	0.0593 (12)	0.0319 (9)	0.0065 (11)	0.0119 (9)	−0.0046 (8)
C2	0.0415 (12)	0.0424 (13)	0.0326 (11)	−0.0008 (10)	0.0060 (9)	0.0002 (9)
C8	0.0551 (16)	0.0537 (16)	0.0421 (14)	−0.0006 (13)	−0.0025 (12)	0.0088 (12)
C7	0.0357 (11)	0.0383 (12)	0.0316 (11)	0.0015 (9)	0.0055 (8)	−0.0022 (9)
C1	0.0570 (15)	0.0357 (12)	0.0327 (11)	0.0021 (11)	0.0068 (10)	0.0021 (9)
C4	0.0551 (16)	0.0606 (17)	0.0398 (13)	−0.0041 (13)	0.0039 (11)	−0.0130 (12)
C6	0.0491 (14)	0.0375 (12)	0.0410 (13)	0.0005 (11)	0.0051 (10)	−0.0003 (10)
C3	0.0521 (15)	0.0540 (15)	0.0332 (12)	−0.0012 (12)	0.0040 (10)	0.0017 (11)
C5	0.0524 (15)	0.0400 (13)	0.0557 (16)	−0.0051 (11)	0.0096 (12)	−0.0138 (12)
C13	0.076 (2)	0.0580 (19)	0.080 (2)	−0.0021 (17)	−0.0227 (19)	0.0045 (17)
C9	0.0559 (18)	0.089 (3)	0.0559 (18)	−0.0019 (17)	0.0029 (14)	−0.0021 (17)
C11	0.060 (2)	0.121 (4)	0.096 (3)	−0.021 (2)	−0.016 (2)	0.039 (3)
C10	0.063 (2)	0.123 (4)	0.072 (2)	0.008 (2)	0.0080 (19)	0.015 (2)
C12	0.081 (3)	0.079 (3)	0.117 (4)	−0.011 (2)	−0.033 (3)	0.016 (3)
C15	0.138 (5)	0.115 (4)	0.186	−0.035 (4)	−0.075 (4)	−0.004 (4)
C14	0.080 (3)	0.185	0.140 (5)	0.021 (4)	0.027 (3)	−0.019 (5)

Geometric parameters (Å, º) top

S1—O3	1.419 (2)	C6—C5	1.388 (4)
S1—O2	1.423 (2)	C6—H6	0.9300
S1—N1	1.6667 (19)	C3—H3	0.9300
S1—C8	1.749 (3)	C13—C12	1.368 (6)
Cl1—C5	1.746 (3)	C13—H13	0.9300
O1—C1	1.210 (3)	C9—C10	1.388 (5)
N2—C1	1.354 (3)	C9—H9	0.9300
N2—C2	1.389 (3)	C11—C12	1.367 (7)
N2—H2	0.8600	C11—C10	1.395 (7)
N1—C7	1.419 (3)	C11—H11	0.9300
N1—C1	1.421 (3)	C10—C14	1.512 (7)
C2—C3	1.376 (3)	C12—C15	1.520 (7)
C2—C7	1.399 (3)	C15—H15A	0.9600
C8—C13	1.375 (4)	C15—H15B	0.9600
C8—C9	1.376 (5)	C15—H15C	0.9600
C7—C6	1.372 (3)	C14—H14A	0.9600
C4—C5	1.385 (4)	C14—H14B	0.9600
C4—C3	1.389 (4)	C14—H14C	0.9600
C4—H4	0.9300

O3—S1—O2	120.41 (13)	C4—C3—H3	121.1
O3—S1—N1	105.25 (11)	C4—C5—C6	123.8 (3)
O2—S1—N1	106.81 (11)	C4—C5—Cl1	119.1 (2)
O3—S1—C8	109.74 (14)	C6—C5—Cl1	117.1 (2)
O2—S1—C8	109.40 (14)	C12—C13—C8	119.6 (4)
N1—S1—C8	103.86 (12)	C12—C13—H13	120.2
C1—N2—C2	111.5 (2)	C8—C13—H13	120.2
C1—N2—H2	124.2	C8—C9—C10	119.0 (4)
C2—N2—H2	124.2	C8—C9—H9	120.5
C7—N1—C1	109.87 (18)	C10—C9—H9	120.5
C7—N1—S1	127.94 (16)	C12—C11—C10	122.8 (4)
C1—N1—S1	120.99 (16)	C12—C11—H11	118.6
C3—C2—N2	130.5 (2)	C10—C11—H11	118.6
C3—C2—C7	121.3 (2)	C9—C10—C11	117.8 (4)
N2—C2—C7	108.2 (2)	C9—C10—C14	119.5 (5)
C13—C8—C9	122.0 (3)	C11—C10—C14	122.7 (4)
C13—C8—S1	120.2 (3)	C11—C12—C13	118.7 (4)
C9—C8—S1	117.7 (2)	C11—C12—C15	119.7 (5)
C6—C7—C2	122.1 (2)	C13—C12—C15	121.5 (5)
C6—C7—N1	132.8 (2)	C12—C15—H15A	109.5
C2—C7—N1	105.1 (2)	C12—C15—H15B	109.5
O1—C1—N2	129.2 (2)	H15A—C15—H15B	109.5
O1—C1—N1	125.6 (2)	C12—C15—H15C	109.5
N2—C1—N1	105.1 (2)	H15A—C15—H15C	109.5
C5—C4—C3	119.6 (2)	H15B—C15—H15C	109.5
C5—C4—H4	120.2	C10—C14—H14A	109.5
C3—C4—H4	120.2	C10—C14—H14B	109.5
C7—C6—C5	115.5 (2)	H14A—C14—H14B	109.5
C7—C6—H6	122.3	C10—C14—H14C	109.5
C5—C6—H6	122.3	H14A—C14—H14C	109.5
C2—C3—C4	117.7 (2)	H14B—C14—H14C	109.5
C2—C3—H3	121.1

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···O1ⁱ	0.86	2.18	2.852 (3)	135 (1)
N2—H2···O2ⁱ	0.86	2.39	3.075 (3)	138 (1)

Symmetry code: (i) x, −y+1/2, z+1/2.

Experimental details

Crystal data
Chemical formula	C₁₅H₁₃ClN₂O₃S
M_r	336.78
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	293
a, b, c (Å)	12.173 (3), 14.036 (3), 8.949 (2)
β (°)	95.77 (2)
V (Å³)	1521.3 (6)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.40
Crystal size (mm)	0.5 × 0.4 × 0.3

Data collection
Diffractometer	Enraf–Nonius CAD-4 diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	3964, 3634, 3214
R_int	0.014
(sin θ/λ)_max (Å⁻¹)	0.661

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.057, 0.133, 1.19
No. of reflections	3634
No. of parameters	199
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.23, −0.27

Computer programs: CAD-4 Software (Enraf–Nonius, 1989), SHELXL97 (Sheldrick, 2008), XCAD4 (Harms & Wocadlo, 1995), SIR92 (Altomare et al., 1994), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···O1ⁱ	0.86	2.18	2.852 (3)	134.8 (9)
N2—H2···O2ⁱ	0.86	2.39	3.075 (3)	137.5 (9)

Symmetry code: (i) x, −y+1/2, z+1/2.

References

Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435. CrossRef Web of Science IUCr Journals Google Scholar
Barreca, L. M., Rao, A., De Luca, L., Iraci, N., Monforte, A. M., Maga, G., De Clercq, E., Pannecouque, C., Balzarini, J. & Chimirri, A. (2007). Bioorg. Med. Chem. Lett. 17, 1956–1960. Web of Science CrossRef PubMed CAS Google Scholar
Barreca, L. M., Rao, A., De Luca, L., Zappala, M., Monforte, A. M., Maga, G., Pannecouque, C., De Clercq, E., Balzarini, J., Chimirri, A. & Monforte, P. (2005). J. Med. Chem. 48, 3433–3437. Web of Science CrossRef PubMed CAS Google Scholar
Beddoes, R. L., Dalton, L., Joule, J. A., Mills, O. S., Street, J. D. & Watt, C. I. F. (1986). J. Chem. Soc. Perkin Trans. 2, pp. 787–797. CSD CrossRef 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
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838. CrossRef CAS IUCr Journals Google Scholar
Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany. Google Scholar
Liu, Y., Gribble, G. W. & Jasinski, J. P. (2007). Acta Cryst. E63, o735–o737. Web of Science CSD CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals 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 1| January 2009| Page o159

doi:10.1107/S1600536808042694

Open

access