The 1:1 adduct of caffeine and 2-(1,3-dioxoisoindolin-2-yl)acetic acid

Bhatti, M.H.; Yunus, U.; Saeed, S.; Shah, S.R.; Wong, W.-T.

doi:10.1107/S1600536811030182

organic compounds

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ISSN: 2056-9890

Volume 67| Part 9| September 2011| Page o2240

doi:10.1107/S1600536811030182

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The 1:1 adduct of caffeine and 2-(1,3-dioxoisoindolin-2-yl)acetic acid

Moazzam H. Bhatti,^a Uzma Yunus,^a Sohail Saeed,^a ^* Syed Raza Shah ^a and Wing-Tak Wong ^b

^aDepartment of Chemistry, Research Complex, Allama Iqbal Open University, Islamabad 44000, Pakistan, and ^bDepartment of Chemistry, The University of Hong Kong, Pokfulam Road, Pokfulam, Hong Kong SAR, People's Republic of China
^*Correspondence e-mail: sohail262001@yahoo.com

(Received 3 July 2011; accepted 26 July 2011; online 2 August 2011)

In the crystal structure of the title adduct [systematic name: 2-(1,3-dioxoisoindolin-2-yl)acetic acid–1,3,7-trimethyl-1,2,3,6-tetrahydro-7H-purine-2,6-dione (1/1)], C₈H₁₀N₄O₂·C₁₀H₇NO₄, the components are linked by an O—H⋯N hydrogen-bond and no proton transfer occurs.

Related literature

For background to N-phthaloylglycine and its derivatives, see: Antunes et al. (1998 ); Barooah et al. (2006a ,b ); Khan & Ismail (2002 ); Shariat & Abdollahi (2004 ); Yunus et al. (2008 ).

Experimental

Crystal data

C₈H₁₀N₄O₂·C₁₀H₇NO₄
M_r = 399.37
Monoclinic, P 2₁ /n
a = 14.6595 (5) Å
b = 4.6567 (2) Å
c = 26.5281 (8) Å
β = 101.408 (2)°
V = 1775.16 (11) Å³
Z = 4
Mo Kα radiation
μ = 0.12 mm⁻¹
T = 296 K
0.48 × 0.16 × 0.10 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2008b ) T_min = 0.947, T_max = 0.989
20916 measured reflections
3373 independent reflections
2268 reflections with I > 2σ(I)
R_int = 0.045

Refinement

R[F² > 2σ(F²)] = 0.044
wR(F²) = 0.130
S = 1.03
3373 reflections
269 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.20 e Å⁻³
Δρ_min = −0.21 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯N5	0.98 (3)	1.73 (3)	2.707 (2)	171 (3)

Data collection: APEX2 (Bruker, 2007 ); cell refinement: APEX2; data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008a ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008a); molecular graphics: Mercury (Macrae et al., 2008 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811030182/ds2126sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811030182/ds2126Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811030182/ds2126Isup3.cml

checkCIF report

Comment top

Among the N-phthaloylamino acids, N-phthaloylglycine is the most widely studied for cleavage with various amines (Khan & Ismail, 2002), metal complexes with interesting supramolecular structures (Barooah et al., 2006a) and adduct formation with various aromatic amines and hydroxyl aromatics (Barooah et al., 2006b). The heterocyclic derivatives are also known in the literature such as oxadizaole (Antunes et al., 1998), benzoxazinone (Shariat & Abdollahi, 2004) and 1,2,4-triazole (Yunus et al., 2008).

In an attempt to synthesis calcium(II) complex of N-phthaloylglycine and caffeine, we have obtained 1:1 adduct of N-phthaloylglycine and caffeine as title compound (I). The 1,3,7-trimethyl-hexahydro-purine-2,6-dione, C₈H₁₀N₄O₂, and (1,3-dioxo-1,3-dihydro-isoindol-2-yl)-acetic acid, C₁₀H₇NO₄, co-crystallizes in a primitive monoclinic space group, P2₁/n (#14). The acetic acid group is about 74.96 (5)° from the ring plane of isoindole-1,3-dione.

C—O distances [C1—O2 = 1.200 (2); C1—O1 = 1.316 (2) Å) of the COOH moiety suggests that no proton transfer has taken place. There are inter-molecular O—H···N H-bond interactions which link the two molecules together.

Related literature top

For background on N-phthaloylglycine and its derivatives, see: Antunes et al. (1998); Barooah et al. (2006a,b); Khan & Ismail (2002); Shariat & Abdollahi (2004); Yunus et al. (2008).

Experimental top

A mixture of CaCO₃ (0.005 mol), N-phthaloylglycine (0.01 mol) and caffeine (0.005 mol) was heated in water (100 ml) for 2 h. The hot solution was filtered and filtrate was set aside for one week. Colourless needle like crystals were obtained suitable for X-ray analysis.

Computing details top

Data collection: APEX2 (Bruker, 2007); cell refinement: APEX2 (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008a); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008a); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008a).

Figures top

Fig. 1. The ORTEP plot of the co-crystal was shown at 50% probability thermal ellipsoids with the atom numbering scheme.

2-(1,3-dioxoisoindolin-2-yl)acetic acid– 1,3,7-trimethyl-1,2,3,6-tetrahydro-7H-purine-2,6-dione (1/1) top

Crystal data top

C₈H₁₀N₄O₂·C₁₀H₇NO₄	F(000) = 832
M_r = 399.37	D_x = 1.494 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 2850 reflections
a = 14.6595 (5) Å	θ = 2.9–23.0°
b = 4.6567 (2) Å	µ = 0.12 mm⁻¹
c = 26.5281 (8) Å	T = 296 K
β = 101.408 (2)°	Needle, colourless
V = 1775.16 (11) Å³	0.48 × 0.16 × 0.10 mm
Z = 4

Data collection top

Bruker APEXII CCD diffractometer	3373 independent reflections
Radiation source: fine-focus sealed tube	2268 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.045
ω and ϕ scan	θ_max = 25.7°, θ_min = 1.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 2008b)	h = −17→17
T_min = 0.947, T_max = 0.989	k = −5→5
20916 measured reflections	l = −32→32

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)] = 0.044	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.130	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ²(F_o²) + (0.0683P)² + 0.2661P] where P = (F_o² + 2F_c²)/3
3373 reflections	(Δ/σ)_max = 0.005
269 parameters	Δρ_max = 0.20 e Å⁻³
0 restraints	Δρ_min = −0.21 e Å⁻³

Crystal data top

C₈H₁₀N₄O₂·C₁₀H₇NO₄	V = 1775.16 (11) Å³
M_r = 399.37	Z = 4
Monoclinic, P2₁/n	Mo Kα radiation
a = 14.6595 (5) Å	µ = 0.12 mm⁻¹
b = 4.6567 (2) Å	T = 296 K
c = 26.5281 (8) Å	0.48 × 0.16 × 0.10 mm
β = 101.408 (2)°

Data collection top

Bruker APEXII CCD diffractometer	3373 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2008b)	2268 reflections with I > 2σ(I)
T_min = 0.947, T_max = 0.989	R_int = 0.045
20916 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.044	0 restraints
wR(F²) = 0.130	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	Δρ_max = 0.20 e Å⁻³
3373 reflections	Δρ_min = −0.21 e Å⁻³
269 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
O1	0.22787 (11)	0.5983 (3)	0.16097 (6)	0.0524 (4)
H1	0.293 (2)	0.537 (6)	0.1631 (11)	0.096 (9)*
O2	0.29779 (10)	0.9442 (3)	0.21235 (6)	0.0574 (4)
O3	−0.01236 (11)	0.5371 (4)	0.21311 (6)	0.0592 (4)
O4	0.08996 (11)	1.0227 (4)	0.08551 (6)	0.0630 (5)
O5	0.68437 (11)	0.0115 (4)	0.15118 (7)	0.0657 (5)
O6	0.42324 (13)	−0.2400 (4)	0.03383 (6)	0.0715 (5)
N1	0.05672 (10)	0.8102 (4)	0.15825 (6)	0.0416 (4)
N2	0.55660 (11)	0.4293 (4)	0.19480 (6)	0.0420 (4)
N3	0.55304 (13)	−0.1112 (4)	0.09235 (7)	0.0489 (5)
N4	0.40577 (12)	0.0946 (4)	0.09313 (6)	0.0440 (4)
N5	0.40629 (11)	0.4590 (4)	0.15872 (6)	0.0409 (4)
C1	0.22844 (14)	0.8265 (5)	0.19031 (8)	0.0408 (5)
C2	0.13310 (13)	0.9294 (5)	0.19542 (8)	0.0459 (5)
H2A	0.1237	0.8825	0.2297	0.055*
H2B	0.1313	1.1369	0.1922	0.055*
C3	0.04313 (14)	0.8602 (5)	0.10534 (8)	0.0451 (5)
C4	−0.03699 (14)	0.6796 (5)	0.08152 (8)	0.0430 (5)
C5	−0.07858 (17)	0.6416 (6)	0.03054 (9)	0.0577 (6)
H5	−0.0582	0.7406	0.0044	0.069*
C6	−0.15203 (19)	0.4493 (6)	0.02013 (10)	0.0683 (8)
H6	−0.1806	0.4149	−0.0139	0.082*
C7	−0.18374 (17)	0.3079 (6)	0.05892 (11)	0.0683 (7)
H7	−0.2340	0.1831	0.0505	0.082*
C8	−0.14258 (15)	0.3469 (5)	0.11024 (10)	0.0568 (6)
H8	−0.1640	0.2516	0.1364	0.068*
C9	−0.06796 (13)	0.5348 (5)	0.12049 (8)	0.0434 (5)
C10	−0.00813 (14)	0.6162 (5)	0.17002 (8)	0.0425 (5)
C11	0.47493 (14)	0.5566 (5)	0.19502 (8)	0.0420 (5)
H11	0.4670	0.6994	0.2183	0.050*
C12	0.54018 (13)	0.2291 (4)	0.15529 (7)	0.0389 (5)
C13	0.60057 (15)	0.0424 (5)	0.13510 (9)	0.0466 (6)
C14	0.45764 (16)	−0.0942 (5)	0.07064 (8)	0.0488 (6)
C15	0.44793 (13)	0.2549 (4)	0.13435 (7)	0.0372 (5)
C16	0.64351 (16)	0.4833 (6)	0.23127 (9)	0.0610 (7)
H16A	0.6928	0.5142	0.2128	0.073*
H16B	0.6582	0.3206	0.2536	0.073*
H16C	0.6366	0.6506	0.2513	0.073*
C17	0.60798 (19)	−0.3018 (6)	0.06585 (10)	0.0692 (8)
H17A	0.6630	−0.3617	0.0895	0.083*
H17B	0.6253	−0.2010	0.0376	0.083*
H17C	0.5715	−0.4673	0.0531	0.083*
C18	0.30650 (16)	0.1200 (6)	0.07221 (10)	0.0652 (7)
H18A	0.2970	0.1605	0.0361	0.078*
H18B	0.2810	0.2732	0.0893	0.078*
H18C	0.2761	−0.0569	0.0775	0.078*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0379 (9)	0.0535 (10)	0.0644 (10)	0.0043 (7)	0.0064 (7)	−0.0183 (8)
O2	0.0371 (9)	0.0605 (10)	0.0714 (11)	−0.0044 (8)	0.0033 (8)	−0.0154 (8)
O3	0.0578 (10)	0.0744 (11)	0.0468 (9)	0.0017 (9)	0.0134 (8)	0.0143 (8)
O4	0.0560 (10)	0.0731 (11)	0.0613 (11)	−0.0102 (9)	0.0155 (8)	0.0140 (9)
O5	0.0414 (10)	0.0730 (12)	0.0859 (13)	0.0115 (8)	0.0208 (9)	0.0056 (9)
O6	0.0895 (13)	0.0668 (12)	0.0590 (11)	−0.0085 (10)	0.0171 (9)	−0.0233 (10)
N1	0.0319 (9)	0.0526 (10)	0.0395 (10)	0.0017 (8)	0.0047 (7)	0.0017 (8)
N2	0.0363 (9)	0.0465 (10)	0.0430 (10)	−0.0046 (8)	0.0077 (8)	0.0009 (8)
N3	0.0544 (12)	0.0428 (10)	0.0551 (12)	0.0053 (9)	0.0244 (9)	−0.0002 (9)
N4	0.0429 (10)	0.0444 (10)	0.0441 (10)	−0.0007 (8)	0.0071 (8)	−0.0040 (9)
N5	0.0370 (9)	0.0433 (10)	0.0431 (10)	0.0023 (8)	0.0095 (8)	−0.0031 (8)
C1	0.0369 (11)	0.0441 (12)	0.0404 (12)	0.0010 (10)	0.0054 (9)	0.0014 (10)
C2	0.0374 (11)	0.0496 (13)	0.0489 (13)	0.0055 (10)	0.0043 (10)	−0.0073 (10)
C3	0.0381 (11)	0.0517 (13)	0.0464 (13)	0.0073 (10)	0.0105 (10)	0.0073 (11)
C4	0.0374 (11)	0.0473 (12)	0.0435 (12)	0.0077 (10)	0.0058 (9)	−0.0001 (10)
C5	0.0557 (14)	0.0676 (16)	0.0465 (14)	0.0128 (13)	0.0020 (11)	−0.0001 (12)
C6	0.0584 (16)	0.0771 (18)	0.0600 (17)	0.0108 (15)	−0.0113 (13)	−0.0173 (15)
C7	0.0463 (14)	0.0640 (17)	0.089 (2)	−0.0028 (13)	0.0006 (14)	−0.0178 (16)
C8	0.0416 (13)	0.0570 (15)	0.0723 (17)	−0.0018 (11)	0.0123 (12)	−0.0043 (13)
C9	0.0317 (11)	0.0460 (12)	0.0520 (13)	0.0060 (9)	0.0075 (10)	−0.0005 (10)
C10	0.0360 (11)	0.0482 (12)	0.0437 (13)	0.0096 (10)	0.0092 (9)	0.0049 (10)
C11	0.0456 (12)	0.0429 (12)	0.0396 (12)	−0.0009 (10)	0.0132 (10)	−0.0028 (10)
C12	0.0357 (11)	0.0398 (11)	0.0428 (12)	0.0008 (9)	0.0120 (9)	0.0016 (10)
C13	0.0422 (13)	0.0466 (13)	0.0544 (14)	0.0034 (10)	0.0180 (11)	0.0101 (11)
C14	0.0604 (15)	0.0434 (13)	0.0456 (13)	−0.0026 (11)	0.0178 (11)	−0.0010 (11)
C15	0.0382 (11)	0.0367 (11)	0.0382 (11)	−0.0005 (9)	0.0112 (9)	0.0003 (9)
C16	0.0437 (13)	0.0752 (17)	0.0599 (15)	−0.0102 (12)	−0.0005 (11)	−0.0039 (13)
C17	0.0885 (19)	0.0551 (15)	0.0776 (18)	0.0166 (14)	0.0492 (15)	0.0015 (14)
C18	0.0476 (14)	0.0845 (19)	0.0581 (15)	−0.0007 (14)	−0.0024 (11)	−0.0162 (14)

Geometric parameters (Å, º) top

O1—C1	1.316 (2)	C3—C4	1.481 (3)
O1—H1	0.98 (3)	C4—C5	1.380 (3)
O2—C1	1.200 (2)	C4—C9	1.384 (3)
O3—C10	1.214 (2)	C5—C6	1.386 (4)
O4—C3	1.210 (2)	C5—H5	0.9300
O5—C13	1.227 (3)	C6—C7	1.378 (4)
O6—C14	1.214 (3)	C6—H6	0.9300
N1—C10	1.391 (3)	C7—C8	1.388 (3)
N1—C3	1.398 (3)	C7—H7	0.9300
N1—C2	1.448 (2)	C8—C9	1.385 (3)
N2—C11	1.337 (3)	C8—H8	0.9300
N2—C12	1.388 (3)	C9—C10	1.478 (3)
N2—C16	1.461 (3)	C11—H11	0.9300
N3—C13	1.404 (3)	C12—C15	1.362 (3)
N3—C14	1.405 (3)	C12—C13	1.419 (3)
N3—C17	1.468 (3)	C16—H16A	0.9600
N4—C15	1.367 (2)	C16—H16B	0.9600
N4—C14	1.374 (3)	C16—H16C	0.9600
N4—C18	1.456 (3)	C17—H17A	0.9600
N5—C11	1.328 (3)	C17—H17B	0.9600
N5—C15	1.360 (2)	C17—H17C	0.9600
C1—C2	1.509 (3)	C18—H18A	0.9600
C2—H2A	0.9700	C18—H18B	0.9600
C2—H2B	0.9700	C18—H18C	0.9600

C1—O1—H1	107.9 (17)	C7—C8—H8	121.7
C10—N1—C3	111.45 (17)	C4—C9—C8	121.6 (2)
C10—N1—C2	124.52 (17)	C4—C9—C10	108.32 (18)
C3—N1—C2	123.87 (17)	C8—C9—C10	130.1 (2)
C11—N2—C12	106.23 (16)	O3—C10—N1	125.0 (2)
C11—N2—C16	125.80 (19)	O3—C10—C9	128.9 (2)
C12—N2—C16	127.89 (18)	N1—C10—C9	106.19 (17)
C13—N3—C14	126.66 (18)	N5—C11—N2	113.31 (18)
C13—N3—C17	117.6 (2)	N5—C11—H11	123.3
C14—N3—C17	115.7 (2)	N2—C11—H11	123.3
C15—N4—C14	119.71 (18)	C15—C12—N2	105.00 (17)
C15—N4—C18	121.35 (18)	C15—C12—C13	122.92 (19)
C14—N4—C18	118.94 (19)	N2—C12—C13	131.95 (19)
C11—N5—C15	103.71 (16)	O5—C13—N3	121.6 (2)
O2—C1—O1	124.22 (19)	O5—C13—C12	126.7 (2)
O2—C1—C2	121.44 (19)	N3—C13—C12	111.71 (18)
O1—C1—C2	114.33 (18)	O6—C14—N4	122.0 (2)
N1—C2—C1	114.98 (17)	O6—C14—N3	121.3 (2)
N1—C2—H2A	108.5	N4—C14—N3	116.71 (19)
C1—C2—H2A	108.5	N5—C15—C12	111.75 (17)
N1—C2—H2B	108.5	N5—C15—N4	125.98 (18)
C1—C2—H2B	108.5	C12—C15—N4	122.25 (18)
H2A—C2—H2B	107.5	N2—C16—H16A	109.5
O4—C3—N1	124.1 (2)	N2—C16—H16B	109.5
O4—C3—C4	129.8 (2)	H16A—C16—H16B	109.5
N1—C3—C4	106.10 (17)	N2—C16—H16C	109.5
C5—C4—C9	121.5 (2)	H16A—C16—H16C	109.5
C5—C4—C3	130.5 (2)	H16B—C16—H16C	109.5
C9—C4—C3	107.92 (17)	N3—C17—H17A	109.5
C4—C5—C6	116.9 (2)	N3—C17—H17B	109.5
C4—C5—H5	121.5	H17A—C17—H17B	109.5
C6—C5—H5	121.5	N3—C17—H17C	109.5
C7—C6—C5	121.6 (2)	H17A—C17—H17C	109.5
C7—C6—H6	119.2	H17B—C17—H17C	109.5
C5—C6—H6	119.2	N4—C18—H18A	109.5
C6—C7—C8	121.7 (2)	N4—C18—H18B	109.5
C6—C7—H7	119.2	H18A—C18—H18B	109.5
C8—C7—H7	119.2	N4—C18—H18C	109.5
C9—C8—C7	116.6 (2)	H18A—C18—H18C	109.5
C9—C8—H8	121.7	H18B—C18—H18C	109.5

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N5	0.98 (3)	1.73 (3)	2.707 (2)	171 (3)

Experimental details

Crystal data
Chemical formula	C₈H₁₀N₄O₂·C₁₀H₇NO₄
M_r	399.37
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	296
a, b, c (Å)	14.6595 (5), 4.6567 (2), 26.5281 (8)
β (°)	101.408 (2)
V (Å³)	1775.16 (11)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.12
Crystal size (mm)	0.48 × 0.16 × 0.10

Data collection
Diffractometer	Bruker APEXII CCD diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 2008b)
T_min, T_max	0.947, 0.989
No. of measured, independent and observed [I > 2σ(I)] reflections	20916, 3373, 2268
R_int	0.045
(sin θ/λ)_max (Å⁻¹)	0.610

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.044, 0.130, 1.03
No. of reflections	3373
No. of parameters	269
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.20, −0.21

Computer programs: APEX2 (Bruker, 2007), SAINT (Bruker, 2007), SHELXS97 (Sheldrick, 2008a), SHELXL97 (Sheldrick, 2008a), Mercury (Macrae et al., 2008).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N5	0.98 (3)	1.73 (3)	2.707 (2)	171 (3)

Acknowledgements

SS is grateful to The University of Hong Kong for providing the facility of crystallographic studies.

References

Antunes, R., Batista, H., Srivastava, R. M., Thomas, G. & Araujo, C. C. (1998). Bioorg. Med. Chem. Lett. 8, 3071–3076. Web of Science CrossRef CAS PubMed Google Scholar
Barooah, N., Sarma, R. J., Batsanov, A. S. & Baruah, J. B. (2006a). Polyhedron, 25, 17–24. Web of Science CSD CrossRef CAS Google Scholar
Barooah, N., Sarma, R. J., Batsanov, A. S. & Baruah, J. B. (2006b). J. Mol. Struct. 791, 122–130. Web of Science CSD CrossRef CAS Google Scholar
Bruker (2007). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Khan, M. N. & Ismail, N. H. (2002). J. Chem. Res. 12, 593–595. CrossRef Google Scholar
Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466–470. Web of Science CrossRef CAS IUCr Journals Google Scholar
Shariat, M. & Abdollahi, S. (2004). Molecules, 9, 705–712. Web of Science CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (2008a). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2008b). SADABS. University of Göttingen, Germany. Google Scholar
Yunus, U., Tahir, M. K., Bhatti, M. H., Yousaf, N. & Helliwell, M. (2008). Acta Cryst. E64, o476–o477. Web of Science CSD CrossRef IUCr Journals Google Scholar