supplementary materials


HTML versionpdf versioncif file3d viewstructure factorssupplementary materialsCIF check reportsimilar papers Open access

cv6646 scheme

Acta Cryst. (2011). E67, m1164-m1165    [ doi:10.1107/S1600536811029941 ]

Diaquabis(N,N'-diethylnicotinamide-[kappa]N1)bis(4-fluorobenzoato-[kappa]O)copper(II)

H. Necefoglu, F. E. Özbek, V. Öztürk, V. Adigüzel and T. Hökelek

Abstract top

The asymmetric unit of the title mononuclear CuII complex, [Cu(C7H4FO2)2(C10H14N2O)2(H2O)2], contains one-half of the molecule. The CuII ion is located on an inversion centre, and is coordinated by two N atoms from two diethylnicotinamide ligands, two O atoms from two 4-fluorobenzoate (PFB) ligands and two water molecules in a distorted octahedral geometry. In the PFB ligand, the carboxylate group is twisted at an angle of 2.10 (14)° from the attached benzene ring. In the crystal structure, intermolecular O-H...O hydrogen bonds link molecules related by translation along the a axis into chains. Weak intermolecular C-H...O hydrogen bonds and [pi]-[pi] interactions between the pyridine rings of neighbouring molecules [centroid-to-centroid distance = 3.571 (2) Å] further consolidate the crystal packing.

Comment top

As a part of our ongoing investigations of transition metal complexes of nicotinamide (NA), one form of niacin (Krishnamachari, 1974), and/or the nicotinic acid derivative N,N-diethylnicotinamide (DENA), an important respiratory stimulant (Bigoli et al., 1972), the title compound was synthesized. Herewith we report its crystal structure (Fig. 1).

The asymmetric unit of the title mononuclear CuII complex contains one-half molecule, the CuII atom being located on an inversion center. The unit cell of the title compound contains also two N,N-diethylnicotinamide (DENA) ligands, two 4-fluorobenzoato (PFB) ligands and two coordinated water molecules. All ligands coordinate the Cu in a monodentate manner. The crystal structures of similar omplexes of CuII, CoII, NiII, MnII and ZnII ions, [Cu(C7H5O2)2(C10H14N2O)2] (Hökelek et al., 1996), [Co(C6H6N2O)2(C7H4NO4)2(H2O)2] (Hökelek & Necefoğlu, 1998), [Co(C9H9O2)2(C10H14N2O)2(H2O)2] (Necefoğlu et al., 2011), [Ni(C7H4ClO2)2(C6H6N2O)2(H2O)2] (Hökelek et al., 2009a), [Mn(C9H10NO2)2(H2O)4].2H2O (Hökelek & Necefoğlu, 2007) and [Zn(C7H4BrO2)2(C6H6N2O)2(H2O)2] (Hökelek et al., 2009b) have also been reported. In the copper(II) complex mentioned above the two benzoate ions coordinate to the CuII atom as bidentate ligands, while in the other structures all the ligands coordinate in a monodentate manner.

In the title complex, four O atoms (O1, O1', O4 and O4', see Fig. 1) in the equatorial plane around the CuII ion form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by the two N atoms of the DENA ligands (N1 and N1') in the axial positions. The near equalities of the C1—O1 [1.2716 (19) Å] and C1—O2 [1.247 (2) Å] bonds in the carboxylate groups indicate delocalized bonding arrangements, rather than localized single and double bonds. The Cu—O bond lengths are 1.9833 (11) Å (for benzoate oxygen) and 2.4192 (12) Å (for water oxygen), and the Cu—N bond length is 2.0192 (14) Å, close to standard values (Allen et al., 1987). The Cu atom is displaced out of the mean plane of the carboxylate group (O1/C1/O2) by 0.7971 (1) Å. The dihedral angle between the planar carboxylate group and the adjacent benzene ring A (C2–C7) is 2.10 (14)°. The benzene A (C2–C7) and the pyridine B (N1/C8–C12) rings are oriented at a dihedral angle of A/B = 76.11 (6)°.

In the crystal structure, intermolecular O—H···O hydrogen bonds (Table 1) link the molecules related by translation along axis a into chains. Weak intermolecular C—H···O hydrogen bonds (Table 1) and π–π interactions between the pyridine rings from the neighbouring molecules [Cg1···Cg1i = 3.571 (2) Å; symmetry code: (i) 2 - x, 1 - y, -z; Cg1 is the centroid of N1/C8—C12] consolidate further the crystal packing.

Related literature top

For background to niacin, see: Krishnamachari (1974). For infomation on the nicotinic acid derivative N,N-diethylnicotinamide, see: Bigoli et al. (1972). For related structures, see: Hökelek et al. (1996, 2009a,b); Hökelek & Necefoğlu (1998, 2007); Necefoğlu et al. (2011). For bond-length data, see: Allen et al. (1987).

Experimental top

The title compound was prepared by the reaction of CuSO4.5H2O (1.23 g, 5 mmol) in H2O (20 ml) and DENA (1.78 g, 10 mmol) in H2O (20 ml) with sodium 4-fluorobenzoate (1.62 g, 10 mmol) in H2O (50 ml) at room temperature. The mixture was filtered and set aside to crystallize at ambient temperature for a week, giving blue single crystals.

Refinement top

Atoms H41 and H42 (for water molecules) were located in a difference Fourier map and isotropically refined. The C-bound H atoms were positioned geometrically with C—H = 0.93–0.97 Å, and constrained to ride on their parent atoms, with Uiso(H) = 1.2–1.5Ueq(C).

Computing details top

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); 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); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title molecule with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level [symmetry code ('): -x, -y, -z].
Diaquabis(N,N'-diethylnicotinamide-κN1)bis(4- fluorobenzoato-κO)copper(II) top
Crystal data top
[Cu(C7H4FO2)2(C10H14N2O)2(H2O)2]Z = 1
Mr = 734.25F(000) = 383
Triclinic, P1Dx = 1.448 Mg m−3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 7.4802 (2) ÅCell parameters from 9044 reflections
b = 8.6753 (2) Åθ = 2.9–28.4°
c = 14.6695 (4) ŵ = 0.72 mm−1
α = 77.164 (3)°T = 100 K
β = 84.723 (4)°Block, blue
γ = 65.151 (2)°0.48 × 0.32 × 0.21 mm
V = 842.23 (4) Å3
Data collection top
Bruker Kappa APEXII CCD area-detector
diffractometer		4109 independent reflections
Radiation source: fine-focus sealed tube3714 reflections with I > 2σ(I)
graphiteRint = 0.025
φ and ω scansθmax = 28.5°, θmin = 1.4°
Absorption correction: multi-scan
(SADABS; Bruker, 2007)		h = −9→9
Tmin = 0.759, Tmax = 0.860k = −11→11
13620 measured reflectionsl = −19→19
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.033Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.099H atoms treated by a mixture of independent and constrained refinement
S = 1.15 w = 1/[σ2(Fo2) + (0.0524P)2 + 0.2704P]
where P = (Fo2 + 2Fc2)/3
4109 reflections(Δ/σ)max < 0.001
233 parametersΔρmax = 0.57 e Å−3
2 restraintsΔρmin = −0.45 e Å−3
Crystal data top
[Cu(C7H4FO2)2(C10H14N2O)2(H2O)2]γ = 65.151 (2)°
Mr = 734.25V = 842.23 (4) Å3
Triclinic, P1Z = 1
a = 7.4802 (2) ÅMo Kα radiation
b = 8.6753 (2) ŵ = 0.72 mm−1
c = 14.6695 (4) ÅT = 100 K
α = 77.164 (3)°0.48 × 0.32 × 0.21 mm
β = 84.723 (4)°
Data collection top
Bruker Kappa APEXII CCD area-detector
diffractometer		4109 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2007)		3714 reflections with I > 2σ(I)
Tmin = 0.759, Tmax = 0.860Rint = 0.025
13620 measured reflectionsθmax = 28.5°
Refinement top
R[F2 > 2σ(F2)] = 0.033H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.099Δρmax = 0.57 e Å−3
S = 1.15Δρmin = −0.45 e Å−3
4109 reflectionsAbsolute structure: ?
233 parametersFlack parameter: ?
2 restraintsRogers parameter: ?
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
xyzUiso*/Ueq
Cu10.00000.00000.00000.01357 (9)
O10.16849 (16)−0.15368 (15)0.10899 (8)0.0158 (2)
O2−0.04849 (17)−0.19328 (17)0.21759 (8)0.0203 (3)
O3−0.43885 (17)−0.29279 (17)−0.12427 (8)0.0201 (3)
O40.29700 (18)0.01961 (18)−0.07056 (9)0.0209 (3)
H410.242 (4)0.068 (3)−0.1223 (13)0.047 (8)*
H420.382 (3)−0.074 (2)−0.0817 (16)0.032 (6)*
N10.03309 (19)−0.20678 (18)−0.05247 (9)0.0140 (3)
N2−0.2966 (2)−0.34165 (19)−0.26337 (10)0.0170 (3)
F10.65236 (17)−0.32105 (18)0.47171 (7)0.0329 (3)
C10.1133 (2)−0.1884 (2)0.19273 (11)0.0144 (3)
C20.2588 (2)−0.2244 (2)0.26753 (11)0.0149 (3)
C30.2080 (2)−0.2568 (2)0.36158 (11)0.0177 (3)
H30.0846−0.25640.37770.021*
C40.3405 (3)−0.2895 (2)0.43123 (12)0.0209 (4)
H40.3080−0.31100.49410.025*
C50.5214 (3)−0.2892 (2)0.40410 (12)0.0212 (4)
C60.5773 (2)−0.2567 (2)0.31234 (12)0.0197 (3)
H60.7008−0.25680.29700.024*
C70.4429 (2)−0.2236 (2)0.24351 (11)0.0159 (3)
H70.4761−0.20060.18080.019*
C80.2015 (2)−0.3509 (2)−0.04352 (11)0.0158 (3)
H80.3068−0.3555−0.01220.019*
C90.2241 (2)−0.4928 (2)−0.07912 (11)0.0170 (3)
H90.3423−0.5912−0.07110.020*
C100.0693 (2)−0.4873 (2)−0.12681 (11)0.0159 (3)
H100.0819−0.5808−0.15190.019*
C11−0.1058 (2)−0.3376 (2)−0.13609 (10)0.0141 (3)
C12−0.1186 (2)−0.2029 (2)−0.09675 (11)0.0141 (3)
H12−0.2374−0.1052−0.10110.017*
C13−0.2925 (2)−0.3226 (2)−0.17555 (11)0.0148 (3)
C14−0.1364 (3)−0.3544 (3)−0.33111 (12)0.0215 (4)
H14A−0.1352−0.4266−0.37320.026*
H14B−0.0117−0.4107−0.29790.026*
C15−0.1552 (3)−0.1797 (3)−0.38791 (16)0.0354 (5)
H15A−0.0445−0.1953−0.42930.053*
H15B−0.1584−0.1069−0.34660.053*
H15C−0.2747−0.1262−0.42390.053*
C16−0.4830 (2)−0.3304 (2)−0.29629 (13)0.0211 (4)
H16A−0.5377−0.3920−0.24650.025*
H16B−0.4550−0.3885−0.34860.025*
C17−0.6367 (3)−0.1461 (3)−0.32646 (15)0.0288 (4)
H17A−0.7545−0.1488−0.34550.043*
H17B−0.5866−0.0855−0.37780.043*
H17C−0.6660−0.0874−0.27510.043*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu10.01438 (14)0.01390 (16)0.01479 (14)−0.00694 (11)−0.00242 (9)−0.00428 (10)
O10.0159 (5)0.0163 (6)0.0160 (5)−0.0067 (5)−0.0017 (4)−0.0041 (4)
O20.0151 (6)0.0250 (7)0.0224 (6)−0.0102 (5)−0.0015 (4)−0.0035 (5)
O30.0144 (5)0.0262 (7)0.0218 (6)−0.0087 (5)0.0012 (4)−0.0092 (5)
O40.0163 (6)0.0227 (7)0.0216 (6)−0.0052 (5)0.0000 (5)−0.0063 (5)
N10.0131 (6)0.0153 (7)0.0159 (6)−0.0077 (5)0.0011 (5)−0.0044 (5)
N20.0141 (6)0.0198 (7)0.0189 (6)−0.0069 (5)−0.0020 (5)−0.0063 (5)
F10.0312 (6)0.0496 (8)0.0231 (5)−0.0225 (6)−0.0122 (4)−0.0007 (5)
C10.0147 (7)0.0100 (7)0.0197 (7)−0.0047 (6)−0.0021 (6)−0.0052 (6)
C20.0156 (7)0.0122 (8)0.0176 (7)−0.0056 (6)−0.0011 (6)−0.0045 (6)
C30.0167 (7)0.0172 (8)0.0206 (8)−0.0080 (6)0.0000 (6)−0.0047 (6)
C40.0250 (9)0.0235 (9)0.0157 (7)−0.0116 (7)−0.0011 (6)−0.0029 (7)
C50.0227 (8)0.0231 (9)0.0204 (8)−0.0109 (7)−0.0082 (6)−0.0033 (7)
C60.0160 (8)0.0209 (9)0.0240 (8)−0.0091 (7)−0.0024 (6)−0.0039 (7)
C70.0170 (7)0.0148 (8)0.0168 (7)−0.0073 (6)−0.0007 (6)−0.0034 (6)
C80.0135 (7)0.0177 (8)0.0166 (7)−0.0064 (6)−0.0002 (5)−0.0044 (6)
C90.0129 (7)0.0174 (8)0.0193 (7)−0.0041 (6)−0.0006 (6)−0.0051 (6)
C100.0164 (7)0.0144 (8)0.0183 (7)−0.0064 (6)0.0011 (6)−0.0065 (6)
C110.0141 (7)0.0158 (8)0.0149 (7)−0.0082 (6)−0.0002 (5)−0.0037 (6)
C120.0126 (7)0.0143 (8)0.0162 (7)−0.0059 (6)−0.0008 (5)−0.0036 (6)
C130.0145 (7)0.0121 (8)0.0188 (7)−0.0055 (6)−0.0020 (6)−0.0037 (6)
C140.0196 (8)0.0264 (10)0.0183 (8)−0.0075 (7)0.0001 (6)−0.0081 (7)
C150.0334 (11)0.0348 (12)0.0418 (11)−0.0194 (9)0.0083 (9)−0.0077 (10)
C160.0186 (8)0.0229 (9)0.0255 (8)−0.0082 (7)−0.0068 (6)−0.0099 (7)
C170.0203 (9)0.0243 (10)0.0397 (10)−0.0036 (7)−0.0097 (7)−0.0097 (8)
Geometric parameters (Å, °) top
Cu1—O11.9833 (11)C6—H60.9300
Cu1—O1i1.9833 (11)C7—C61.388 (2)
Cu1—O42.4192 (12)C7—H70.9300
Cu1—O4i2.4192 (12)C8—H80.9300
Cu1—N12.0192 (14)C9—C81.382 (2)
Cu1—N1i2.0192 (14)C9—C101.385 (2)
O1—C11.2716 (19)C9—H90.9300
O2—C11.247 (2)C10—H100.9300
O3—C131.2363 (19)C11—C101.395 (2)
O4—H410.831 (17)C11—C131.505 (2)
O4—H420.833 (16)C12—C111.379 (2)
N1—C81.342 (2)C12—H120.9300
N1—C121.343 (2)C14—C151.514 (3)
N2—C131.339 (2)C14—H14A0.9700
N2—C141.467 (2)C14—H14B0.9700
N2—C161.475 (2)C15—H15A0.9600
F1—C51.3601 (19)C15—H15B0.9600
C1—C21.505 (2)C15—H15C0.9600
C2—C31.395 (2)C16—C171.519 (3)
C2—C71.393 (2)C16—H16A0.9700
C3—C41.388 (2)C16—H16B0.9700
C3—H30.9300C17—H17A0.9600
C4—C51.376 (3)C17—H17B0.9600
C4—H40.9300C17—H17C0.9600
C6—C51.376 (2)
O1—Cu1—O1i180.00 (9)C6—C7—C2120.55 (15)
O1—Cu1—O485.97 (4)C6—C7—H7119.7
O1i—Cu1—O494.03 (4)N1—C8—C9122.39 (15)
O1—Cu1—O4i94.03 (4)N1—C8—H8118.8
O1i—Cu1—O4i85.97 (4)C9—C8—H8118.8
O4i—Cu1—O4180.00 (9)C8—C9—C10119.52 (15)
N1—Cu1—O494.85 (5)C8—C9—H9120.2
N1i—Cu1—O485.15 (5)C10—C9—H9120.2
N1—Cu1—O4i85.15 (5)C9—C10—C11118.13 (16)
N1i—Cu1—O4i94.85 (5)C9—C10—H10120.9
O1—Cu1—N191.11 (5)C11—C10—H10120.9
O1i—Cu1—N188.89 (5)C10—C11—C13123.54 (15)
O1—Cu1—N1i88.89 (5)C12—C11—C10118.98 (15)
O1i—Cu1—N1i91.11 (5)C12—C11—C13116.96 (14)
N1i—Cu1—N1180.00 (6)N1—C12—C11122.80 (15)
C1—O1—Cu1127.30 (10)N1—C12—H12118.6
Cu1—O4—H4191.8 (19)C11—C12—H12118.6
Cu1—O4—H42114.0 (17)O3—C13—N2122.08 (15)
H41—O4—H42102 (2)O3—C13—C11117.74 (14)
C8—N1—Cu1122.34 (11)N2—C13—C11120.18 (14)
C8—N1—C12118.14 (15)N2—C14—C15113.02 (15)
C12—N1—Cu1119.51 (11)N2—C14—H14A109.0
C13—N2—C14124.35 (14)N2—C14—H14B109.0
C13—N2—C16117.12 (14)C15—C14—H14A109.0
C14—N2—C16118.20 (14)C15—C14—H14B109.0
O1—C1—C2115.78 (14)H14A—C14—H14B107.8
O2—C1—O1126.09 (14)C14—C15—H15A109.5
O2—C1—C2118.12 (14)C14—C15—H15B109.5
C3—C2—C1119.85 (14)C14—C15—H15C109.5
C7—C2—C1120.43 (14)H15A—C15—H15B109.5
C7—C2—C3119.72 (15)H15A—C15—H15C109.5
C2—C3—H3119.8H15B—C15—H15C109.5
C4—C3—C2120.43 (16)N2—C16—C17114.09 (15)
C4—C3—H3119.8N2—C16—H16A108.7
C3—C4—H4121.1N2—C16—H16B108.7
C5—C4—C3117.76 (15)C17—C16—H16A108.7
C5—C4—H4121.1C17—C16—H16B108.7
F1—C5—C4118.30 (15)H16A—C16—H16B107.6
F1—C5—C6117.84 (16)C16—C17—H17A109.5
C6—C5—C4123.86 (15)C16—C17—H17B109.5
C5—C6—C7117.68 (16)C16—C17—H17C109.5
C5—C6—H6121.2H17A—C17—H17B109.5
C7—C6—H6121.2H17A—C17—H17C109.5
C2—C7—H7119.7H17B—C17—H17C109.5
O4i—Cu1—O1—C1−21.24 (14)C14—N2—C16—C17−93.55 (19)
O4—Cu1—O1—C1158.76 (14)O1—C1—C2—C3177.38 (15)
N1i—Cu1—O1—C173.55 (14)O1—C1—C2—C7−1.8 (2)
N1—Cu1—O1—C1−106.45 (14)O2—C1—C2—C3−1.9 (2)
O1—Cu1—N1—C8−35.00 (12)O2—C1—C2—C7178.89 (15)
O1i—Cu1—N1—C8145.00 (12)C1—C2—C3—C4−179.76 (16)
O1—Cu1—N1—C12143.87 (12)C7—C2—C3—C4−0.6 (3)
O1i—Cu1—N1—C12−36.13 (12)C1—C2—C7—C6179.96 (16)
O4i—Cu1—N1—C8−128.95 (12)C3—C2—C7—C60.8 (3)
O4—Cu1—N1—C851.05 (12)C2—C3—C4—C5−0.1 (3)
O4i—Cu1—N1—C1249.92 (12)C3—C4—C5—F1179.97 (16)
O4—Cu1—N1—C12−130.08 (12)C3—C4—C5—C60.7 (3)
Cu1—O1—C1—O230.3 (2)C7—C6—C5—F1−179.76 (16)
Cu1—O1—C1—C2−148.91 (11)C7—C6—C5—C4−0.5 (3)
Cu1—N1—C8—C9179.77 (12)C2—C7—C6—C5−0.3 (3)
C12—N1—C8—C90.9 (2)C10—C9—C8—N10.7 (2)
Cu1—N1—C12—C11178.59 (11)C8—C9—C10—C11−0.7 (2)
C8—N1—C12—C11−2.5 (2)C12—C11—C10—C9−0.8 (2)
C14—N2—C13—O3171.65 (16)C13—C11—C10—C9−172.22 (15)
C14—N2—C13—C11−8.5 (2)C10—C11—C13—O3118.97 (18)
C16—N2—C13—O3−1.6 (2)C10—C11—C13—N2−60.9 (2)
C16—N2—C13—C11178.22 (14)C12—C11—C13—O3−52.6 (2)
C13—N2—C14—C15−89.5 (2)C12—C11—C13—N2127.53 (17)
C16—N2—C14—C1583.7 (2)N1—C12—C11—C102.5 (2)
C13—N2—C16—C1780.1 (2)N1—C12—C11—C13174.46 (14)
Symmetry codes: (i) −x, −y, −z.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O4—H41···O2ii0.83 (2)1.90 (2)2.7050 (19)163 (3)
O4—H42···O3iii0.83 (2)2.01 (2)2.834 (2)172 (2)
C6—H6···O2iii0.932.323.211 (2)162
C10—H10···O2iv0.932.483.394 (2)170
Symmetry codes: (ii) −x, −y, −z; (iii) x+1, y, z; (iv) −x, −y−1, −z.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O4—H41···O2i0.83 (2)1.90 (2)2.7050 (19)163 (3)
O4—H42···O3ii0.83 (2)2.01 (2)2.834 (2)172 (2)
C6—H6···O2ii0.932.323.211 (2)162
C10—H10···O2iii0.932.483.394 (2)170
Symmetry codes: (i) −x, −y, −z; (ii) x+1, y, z; (iii) −x, −y−1, −z.
Acknowledgements top

The authors are indebted to Anadolu University and the Medicinal Plants and Medicine Research Centre of Anadolu University, Eskişehir, Turkey, for the use of the X-ray diffractometer. This work was financially supported by the Scientific and Technological Research Council of Turkey (grant No. 106 T472).

references
References top

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.

Bigoli, F., Braibanti, A., Pellinghelli, M. A. & Tiripicchio, A. (1972). Acta Cryst. B28, 962–966.

Bruker (2007). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.

Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.

Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838.

Hökelek, T., Dal, H., Tercan, B., Özbek, F. E. & Necefoğlu, H. (2009a). Acta Cryst. E65, m466–m467.

Hökelek, T., Dal, H., Tercan, B., Özbek, F. E. & Necefoğlu, H. (2009b). Acta Cryst. E65, m607–m608.

Hökelek, T., Gündüz, H. & Necefoğlu, H. (1996). Acta Cryst. C52, 2470–2473.

Hökelek, T. & Necefoğlu, H. (1998). Acta Cryst. C54, 1242–1244.

Hökelek, T. & Necefoğlu, H. (2007). Acta Cryst. E63, m821–m823.

Krishnamachari, K. A. V. R. (1974). Am. J. Clin. Nutr. 27, 108–111.

Necefoğlu, H., Maracı, A., Özbek, F. E., Tercan, B. & Hökelek, T. (2011). Acta Cryst. E67, m619–m620.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Spek, A. L. (2009). Acta Cryst. D65, 148–155.