Crystal and molecular structure analysis of 7-chloro-5-cyclopropyl-9- methyl-10-(2-nitro-4-trifluromethyl-phenyl)-5,10-dihydro-4,5,6, 10-tetraaza-dibenzo [a, d]cyclohepten-11-one

Article abstract of DOI:10.1080/15421400801914970

The compound 7-chloro-5-cyclopropyl-9-methyl-10-(2-nitro-4-trifluromethyl- phenyl)- 5,10-dihydro-4,5,6,10-tetraaza-dibenzo[a,d]cyclohepten-11-one, C22H15N5O3F3Cl, crystallizes in the monoclinic crystal class under the space group P21/c with cell parameter

Full text of DOI:10.1080/15421400801914970

Mol. Cryst. Liq. Cryst., Vol. 482, pp. 135–144, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400801914970
Crystal and Molecular Structure Analysis of 7-Chloro-
5-cyclopropyl-9-methyl-10-(2-nitro-4-trifluromethyl-
Phenyl)-5,10-dihydro-4,5,6,10-tetraaza-dibenzo
[a, d]cyclohepten-11-one
N. R. Thimmegowda1, G. Sarala2, C. S. Ananda Kumar1,
S. Chandrappa1, S. B. Benaka Prasad1, M. A. Sridhar2,
J. Shashidhara Prasad2, and K. S. Rangappa1
1Department of Studies in Chemistry, University of Mysore,
Manasagangotri, Mysore, India
2Department of Studies in Physics, University of Mysore,
Manasagangotri, Mysore, India
The compound 7-chloro-5-cyclopropyl-9-methyl-10-(2-nitro-4-trifluromethyl-phenyl)-
5,10-dihydro-4,5,6,10-tetraaza-dibenzo[a,d]cyclohepten-11-one, C22H15N5O3F3Cl,
crystallizes in the monoclinic crystal class under the space group P21=c with cell
˚
˚
˚
parameters a ¼ 16.595(7) A, b ¼ 8.775(7) A, c ¼ 14.973(1) A, b ¼ 97.465(4), V ¼
3
˚
2161.9(3) A , Z ¼ 4. The structure was solved by direct methods using SHELXS-
97, and refined using SHELXL-97. The final residual factor is R1 ¼ 0.0604 for
4116 reflections and 342 parameters. The molecular structure exhibits intra-
molecular hydrogen bond of the type CꢀHꢁꢁꢁO.
Keywords: crystal structure; diazepinone derivative; equatorial conformation
INTRODUCTION
Diazepinone represents probably the most important of all structural
classes in drug discovery [1]. The diazepinone nucleus is a fundamen-
tal constituent of a number of natural and synthetic products with
biological activity. The literature survey revealed the drug Nevirapine
and which is made up of diazepinone nucleus was the first NNRTI to
receive regulatory approval for the treatment of HIV-1 infection.
Received September 26, 2007; accepted October 19, 2007.
Address correspondence to Prof. K. S. Rangappa, Department of Studies in Chemistry,
University of Mysore, Manasagangothri, Mysore 570006, India. E-mail: rangappaks@
gmail.com and rangappaks@chemistry.uni-mysore.ac.in
135

136
N. R. Thimmegowda et al.
Further, the literature survey revealed diazepinone derivatives are
found to be anti-HIV [2,3], antitumour [4], antipsychotics [5], and
potential anti-inflammatory agents [6,7].
In continuation of our research work on synthesis and biological
evaluation of novel heterocycles, the title compound was synthesised
and tested for the inhibition with purified PLA2 from Vipera russellii
(Group II; VRV-PL-V), Naja naja (NN-PL-I) snake venom, and par-
tially purified pleural fluid (Group II, PF-PLA2). The results revealed
that the compound 7-chloro-5-cyclopropyl-9-methyl-10-(2-nitro-4-
trifluromethyl-phenyl)-5,10-dihydro-4,5,6,10-tetraaza-dibenzo
[a,d]
cyclohepten-11-one is found to be a very potent in-vitro enzyme inhibi-
tor and exhibit in-vivo anti-inflammatory activity with excellent selec-
tivity [8]. Herein, we report the crystal and molecular structure
studies of the title compound.
EXPERIMENTAL
Melting points were determined using SELACO-650 hot stage melting
point apparatus and are uncorrected. Infrared (IR) spectra were
recorded using a Jasco FTIR-4100 series. Nuclear magnetic resonance
(1H NMR) spectra were recorded on Shimadzu AMX 400-Bruker,
400 MHz spectrometer using DMSO-d6 as a solvent and TMS as inter-
nal standard (chemical shift in d ppm). Spin multiplets are given as
s (singlet), d (doublet), and m (multiplet). Elemental analyses (CHNS)
were obtained on Vario EL III Elementar. Silica gel column chromato-
graphy was performed using Merck 7734 silica gel (60–120 mesh) and
Merck made Thin Layer Chromatography (TLC) plates. The crystal-
lographic measurements were made on a DIPLabo using Imaging
plate system with graphite monochromated radiation (MoKa).
Synthesis of 7-Chloro-5-cyclopropyl-9-methyl-10-(2-nitro-4-
trifluromethyl-phenyl)-5,10-dihydro-4,5,6,10-tetraaza-dibenzo
[a,d] cyclohepten-11-one
To a solution of 7-chloro-5-cyclopropyl-9-methyl-5,10-dihydro-4,5,6,10-
tetraaza-dibenzo [a,d] cyclohepten-11-one (1) in 10 ml of N,N-dimethyl
formamide, were added 4-chloro 3-nitrobenzotrifluride (0.562 g,
2.49 mmol) and anhydrous powdered potassium carbonate (0.688 g,
4.98 mmol). The reaction mixture was heated to 60ꢂC for 6 h. The reac-
tion mixture was monitored by TLC. Upon completion, solvent was
removed under reduced pressure and extracted with ethyl acetate.
The organic layer was dried with anhydrous sodium sulphate, the

Crystal and Molecular Structure Analysis
137
SCHEME 1
solvent was evaporated to get crude product which was purified by
column chromatography over silica gel using hexane: ethyl acetate
(8:2) as an eluent. The pure product obtained was dissolved in acetoni-
trile. Because of the slow evaporation of the solvent, pale yellow crys-
tals developed after seven days. The synthetic method employed for
synthesis is shown in Scheme 1.
Yield: (0.67 g) 82%. Melting point: 228–230ꢂC.
1H NMR (DMSO-d6, 400 MHz): d 8.45 (m, 1 H), 7.25 (m, 1 H), 7.1 (m,
1 H), 7.02 (m, 1 H), 7.68 (m, 1H), 7.1 (m, 1 H), 7.8 (d, 1 H), 2.32 (s, 5 H),
1.7 (s, 3 H).
IR (KBr cmꢀ1): 1678, 1585, 1542, 1138, 100, 3075, 3006.
Anal. Calcd (in %) for C22H15ClF3N5O3: C, 53.94; H, 3.09; N, 14.30.
Found: C, 53.92; H, 3.05; N, 14.26.
Crystal Structure Determination
Single crystal of the title compound suitable for X-ray diffraction stu-
dies was mounted on a glass fibre. The measurements were made on a
DIPLabo Imaging Plate system with graphite monochromated MoKa
radiation. Thirty-six frames of data were collected by the oscillation
method. Image processing and data reduction were done using Denzo
[9]. The structure was solved using SHELXS-97 [10]. The full-matrix
least-squares refinement was done by using SHELXL-97 [11]. The
R1 value for all reflections is 0.0604.
RESULTS AND DISCUSSION
Table 1 gives the details of crystal data, data collection, and refine-
ment. The final atomic coordinates and equivalent thermal
parameters of nonhydrogen atoms are listed in Table 2. Tables 3

138
N. R. Thimmegowda et al.
TABLE 1 Crystal Data and Structure Refinement
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
C22H15ClF3N5O3
489.84
293(2) K
˚
0.71073 A
Monoclinic
P21=c
Cell dimensions
˚
a ¼ 16.595(7) A
˚
b ¼ 8.775(7) A
˚
c ¼ 14.973(1) A
b ¼ 97.465(4)ꢂ
3
˚
Volume
2161.9(3) A
Z
4
Density (calculated)
Absorption coefficient
F000
1.505 Mg=m3
0.239 mmꢀ1
1000
Crystal size
Theta range for data collection
Index ranges
0.25 ꢃ 0.25 ꢃ 0.30 mm
2.63ꢂ to 32.49ꢂ
ꢀ25 ꢄ h ꢄ 24
ꢀ12 ꢄ k ꢄ 13
ꢀ17 ꢄ l ꢄ 17
Reflections collected
11206
Independent reflections
Absorption correction
Refinement method
Data=restraints=parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
6330 [R(int) ¼ 0.0292]
None
Full-matrix least-squares on F2
6330=0=342
1.060
R1 ¼ 0.0604, xR2 ¼ 0.1650
R1 ¼ 0.0940, xR2 ¼ 0.1965
0.030(3)
Extinction coefficient
Largest diff. peak and hole
ꢀ3
˚
0.358 and ꢀ0.382 e ꢁ A
and 4 give the list of bond lengths and bond angles of nonhydrogen
atoms respectively. The schematic diagram of the molecule is given in
Figure 1. Figure 2 gives the ORTEP diagram of the molecule at 30%
probability. The packing of the molecule down the b axis is given in
Figure 3. In synthesis of 7-chloro-5-cyclopropyl-9-methyl-10-(2-nitro-
4-trifluromethyl-phenyl)-5,10-dihydro-4,5,6,10-tetraaza-dibenzo [a, d]
cyclohepten-11-one, the torsion angle about the atoms C23ꢀC22ꢀ
N13ꢀC12 is 52.3(2)ꢂ which indicates that the 2-nitro-4-trifluoro-
methyl-phenyl ring nearly bisects the 7-chloro-5-cyclopropyl-9-
methyl-5,10-dihydro-4,5,6,10-tetraaza-dibenzo [a, d] cyclohepten-11-one.
The torsion angle for cyclopropyl ring about the atoms C6ꢀN5ꢀC17ꢀ
C18 is 90.60(2)ꢂ indicating the equatorial conformation of cyclopropyl

Crystal and Molecular Structure Analysis
139
TABLE 2 Atomic Coordinates and Equivalent Thermal Parameters of the
Nonhydrogen Atoms
Atom
x
y
z
Ueq
Cl1
C2
N3
C4
N5
C6
N7
C8
0.4143(5)
0.3560(1)
0.3719(9)
0.3276(9)
0.3477(8)
0.3788(9)
0.4555(9)
0.4849(1)
0.4416(1)
0.3613(1)
0.3288(1)
0.2396(1)
0.2126(8)
0.2650(9)
0.2520(1)
0.2996(1)
0.3894(1)
0.3605(1)
0.3423(1)
0.1925(8)
0.1882(1)
0.1282(9)
0.0649(1)
ꢀ0.0154(1)
ꢀ0.0339(1)
0.0276(1)
0.1077(1)
0.0778(1)
0.1324(1)
0.0299(1)
ꢀ0.1212(1)
ꢀ0.1319(3)
ꢀ0.1487(1)
ꢀ0.1673(4)
ꢀ0.1711(8)
ꢀ0.1314(6)
ꢀ0.1549(3)
0.6777(8)
0.5371(2)
0.3977(2)
0.2864(2)
0.1367(2)
0.0520(2)
0.0042(2)
ꢀ0.0715(3)
ꢀ0.1020(3)
ꢀ0.0554(3)
0.0237(2)
0.0524(2)
0.1923(2)
0.3134(2)
0.4624(2)
0.5764(2)
0.1204(2)
ꢀ0.0009(3)
0.1629(3)
ꢀ0.0461(2)
0.5049(3)
0.2078(2)
0.1677(2)
0.1760(3)
0.2295(3)
0.2728(3)
0.2598(3)
0.1250(2)
0.1857(2)
0.0362(3)
0.2422(4)
0.324(3)
0.0536(5)
0.0951(1)
0.0712(1)
0.1009(1)
0.0786(1)
0.1563(1)
0.1626(1)
0.2369(2)
0.3071(2)
0.2991(1)
0.2227(1)
0.2075(1)
0.1735(1)
0.1534(1)
0.1808(1)
0.1509(1)
ꢀ0.0002(1)
ꢀ0.0655(1)
ꢀ0.0876(1)
0.2245(1)
0.2389(2)
0.1397(1)
0.1884(1)
0.1497(1)
0.0630(2)
0.0147(1)
0.0528(1)
0.2835(1)
0.3332(1)
0.3104(1)
0.0218(2)
ꢀ0.0464(1)
0.026(2)
0.0805(3)
0.0484(5)
0.0429(3)
0.0359(3)
0.0375(3)
0.0372(4)
0.0470(4)
0.0574(6)
0.0598(6)
0.0513(5)
0.0403(4)
0.0423(4)
0.0387(3)
0.0378(4)
0.0433(4)
0.0494(5)
0.0428(4)
0.0544(5)
0.0565(5)
0.0577(4)
0.0585(5)
0.0402(4)
0.0455(4)
0.0527(5)
0.0542(5)
0.0561(5)
0.0494(5)
0.0540(5)
0.0685(5)
0.0773(6)
0.0750(8)
0.175(1)
C9
C10
C11
C12
N13
C14
C15
C16
C17
C18
C19
O20
C21
C22
C23
C24
C25
C26
C27
N28
O29
O30
C31
F32A
F32B
F33A
F33B
F34A
F34B
0.385(2)
0.2911(2)
0.187(7)
0.211(3)
0.1051(7)
0.158(1)
0.106(5)
0.20(2)
0.196(1)
0.0795(7)
0.0684(2)
ꢀ0.0595(9)
0.0068(9)
0.119(5)
ring with cyclohepten ring. The torsion angle which determines the
position of the oxygen atom (C10ꢀC11ꢀC12ꢀO20) is 40.06(3)ꢂ. The
chlorine atom and methyl moiety substituted for dibenzo cyclohepten
ring are in the anti-periplanar conformation as the torsion angles

140
N. R. Thimmegowda et al.
˚
TABLE 3 Bond Lengths (A)
Atoms
Length
Atoms
Length
Cl1ꢀC2
C2ꢀN3
1.733(2)
1.311(3)
1.376(3)
1.333(2)
1.402(2)
1.406(2)
1.419(2)
1.451(2)
1.331(2)
1.397(2)
1.334(3)
1.374(3)
1.384(3)
1.386(3)
1.489(2)
1.215(2)
1.381(2)
1.430(2)
1.431(2)
1.396(3)
1.385(3)
C17ꢀC18
C18ꢀC19
C22ꢀC27
C22ꢀC23
C23ꢀC24
C23ꢀN28
C24ꢀC25
C25ꢀC26
C25ꢀC31
C26ꢀC27
N28ꢀO29
N28ꢀO30
C31ꢀF34A
C31ꢀF32A
C31ꢀF33B
C31ꢀF33A
C31ꢀF34B
C31ꢀF32B
C15ꢀC21
C17ꢀC19
1.483(3)
1.497(3)
1.379(3)
1.400(2)
1.384(2)
1.460(3)
1.377(3)
1.377(3)
1.504(3)
1.382(3)
1.219(2)
1.219(2)
1.238(9)
1.240(5)
1.247(9)
1.299(7)
1.333(6)
1.337(1)
1.501(3)
1.482(3)
C2ꢀC16
N3ꢀC4
C4ꢀC14
C4ꢀN5
N5ꢀC6
N5ꢀC17
C6ꢀN7
C6ꢀC11
N7ꢀC8
C8ꢀC9
C9ꢀC10
C10ꢀC11
C11ꢀC12
C12ꢀO20
C12ꢀN13
N13ꢀC14
N13ꢀC22
C14ꢀC15
C15ꢀC16
about the atoms Cl1ꢀC2ꢀN3ꢀC4 and C4ꢀC14ꢀC15ꢀC21 are
179.13(1)ꢂ and 178.58(2)ꢂ, respectively. The atoms N5 and N13,
where the cyclopropyl ring and 2-nitro-4-trifluoromethyl-phenyl ring
are substituted, deviate from the plane defined by the atoms N3ꢀ
C2ꢀC16ꢀC15ꢀC14ꢀC13ꢀC12ꢀC11ꢀC10ꢀC9ꢀC8ꢀN7ꢀC6ꢀC5ꢀC4
˚
˚
ꢀC5ꢀC4 by ꢀ1.151(2) A and ꢀ0.943(2) A, respectively. The basic
moiety 7-chloro-5-cyclopropyl-9-methyl-5,10-dihydro-4,5,6,10-tetraaza-
dibenzo[a,d] cyclohepten-11-one is puckered. The total puckering
˚
amplitude for the basic moiety, Q is 2.6443(3) A. The torsion angle
of 33.6(3)ꢂ for the atoms C22ꢀC23ꢀN28ꢀO30 indicates that the nitro
group substituted for the ring 2 is in syn-clinal onformation with ring
2. The fluorine atoms are highly disordered. Hence, the refinement of
the structure is carried out using partial occupancies for the fluorine
atom. The bond lengths and bond angles are in good agreement with
the standard values except for halogens. The bond length CꢀCl is
˚
˚
0.733(2) A which is less than standard value (1.77 A). The packing
of the molecules indicates that the structure exhibits intramolecular
˚
hydrogen bond of the type CꢀHꢁꢁꢁO with a bond length of 3.322(3) A
and a bond angle of 149.

Crystal and Molecular Structure Analysis
TABLE 4 Bond Angles (ꢂ)
141
Atoms
Angle
Atoms
Angle
N3ꢀC2ꢀC16
N3ꢀC2ꢀCl1
125.18(2)
115.13(2)
119.67(2)
116.95(2)
122.97(2)
116.57(2)
120.44(2)
111.55(1)
115.96(2)
116.99(1)
122.99(2)
117.70(2)
119.31(1)
117.28(2)
124.38(2)
117.98(2)
119.10(2)
118.23(2)
118.86(2)
122.11(2)
121.50(2)
120.14(2)
118.36(2)
124.07(1)
118.04(1)
116.71(1)
118.52(2)
120.84(2)
120.52(2)
117.69(2)
118.91(2)
123.39(2)
118.50(2)
116.15(2)
117.34(2)
60.66(2)
C23ꢀC22ꢀN13
123.96(2)
121.07(2)
115.63(2)
123.17(2)
119.78(2)
120.00(2)
119.77(2)
120.2(2)
119.89(2)
121.57(2)
122.87(2)
119.12(2)
117.87(2)
48.1(1)
C24ꢀC23ꢀC22
C16ꢀC2ꢀCl1
C2ꢀN3ꢀC4
C24ꢀC23ꢀN28
C22ꢀC23ꢀN28
N3ꢀC4ꢀC14
N3ꢀC4ꢀN5
C25ꢀC24ꢀC23
C24ꢀC25ꢀC26
C14ꢀC4ꢀN5
C4ꢀN5ꢀC6
C24ꢀC25ꢀC31
C26ꢀC25ꢀC31
C4ꢀN5ꢀC17
C6ꢀN5ꢀC17
N7ꢀC6ꢀC11
N7ꢀC6ꢀN5
C25ꢀC26ꢀC27
C22ꢀC27ꢀC26
O29ꢀN28ꢀO30
O29ꢀN28ꢀC23
C11ꢀC6ꢀN5
C6ꢀN7ꢀC8
O30ꢀN28ꢀC23
F34AꢀC31ꢀF32A
F34AꢀC31ꢀF33B
F32AꢀC31ꢀF33B
F34AꢀC31ꢀF33A
F32AꢀC31ꢀF33A
F33BꢀC31ꢀF33A
F34AꢀC31ꢀF34B
F32AꢀC31ꢀF34B
F33BꢀC31ꢀF34B
F33AꢀC31ꢀF34B
F34AꢀC31ꢀF32B
F32AꢀC31ꢀF32B
F33BꢀC31ꢀF32B
F33AꢀC31ꢀF32B
F34BꢀC31ꢀF32B
F34AꢀC31ꢀC25
F32AꢀC31ꢀC25
F33BꢀC31ꢀC25
F33AꢀC31ꢀC25
F34BꢀC31ꢀC25
F32BꢀC31ꢀC25
F33AꢀF32BꢀC31
F34AꢀF32AꢀC31
F32BꢀF33AꢀC31
F34BꢀF33BꢀC31
F32AꢀF34AꢀC31
F32AꢀF34AꢀF34B
F33BꢀF34BꢀF34A
C31ꢀF34BꢀF34A
N7ꢀC8ꢀC9
117(2)
C8ꢀC9ꢀC10
130.5(1)
135.3(5)
108.9(1)
43(3)
68.4(2)
111.6(1)
57(3)
98.1(8)
104.5(2)
59.1(1)
C9ꢀC10ꢀC11
C10ꢀC11ꢀC6
C10ꢀC11ꢀC12
C6ꢀC11ꢀC12
O20ꢀC12ꢀN13
O20ꢀC12ꢀC11
N13ꢀC12ꢀC11
C12ꢀN13ꢀC14
C12ꢀN13ꢀC22
C14ꢀN13ꢀC22
C15ꢀC14ꢀC4
C15ꢀC14ꢀN13
C4ꢀC14ꢀN13
C16ꢀC15ꢀC14
C16ꢀC15ꢀC21
C14ꢀC15ꢀC21
C2ꢀC16ꢀC15
N5ꢀC17ꢀC19
N5ꢀC17ꢀC18
C19ꢀC17ꢀC18
C17ꢀC18ꢀC19
C17ꢀC19ꢀC18
C27ꢀC22ꢀC23
C27ꢀC22ꢀN13
C31ꢀF34AꢀF34B
F33BꢀF34BꢀC31
95(3)
54.9(2)
135.7(9)
112.9(5)
114.1(3)
114.6(6)
111.7(3)
111.3(3)
111.5(5)
60.9(1)
65.9(9)
64.1(9)
65.2(2)
66.1(7)
59.63(1)
59.71(1)
117.64(2)
118.36(2)
58.9(1)
119.1(1)
104.2(2)
52.7(6)
58.2(1)

142
N. R. Thimmegowda et al.
FIGURE 1 Schematic diagram of the title compound.
FIGURE 2 ORTEP of title compound at 30% probability.

Crystal and Molecular Structure Analysis
143
FIGURE 3 Packing of the molecules down b axis.
ACKNOWLEDGMENTS
The authors are grateful to Department of Science and Technology
and government of India for financial assistance under Projects
SP=I2=FOO=93 and UGC-SAP (Phase I) No. F. 540=10=DRS=2004
(SAP-I).
REFERENCES
[1] Smith, A. L., Stevenson, G. I., Swain, C. J., & Castro, J. L. (1998). Tet. Lett., 39,
8317.
[2] Yoakim, C., Bonneau, P. R., Deziel, R., Doyon, L., Duan, J., Guse, I., Landry, S.,
Malenfant, E., Naud, J., Ogilvie, W. W., OMeara, J. A., Plante, R., Simoneau, B.,
Thavonekham, B., Bos, M., & Cordingley, M. G. (2004). Bioorg. Med. Chem. Lett.,
14, 739.
[3] Hargrave, K. D., Proudfoot, J. R., Grozinger, K. G., Cullen, E., Kapadia, S. R., Patel,
U. R., Fuchs, V. U., Mauldin, S. C., Vitous, J., Behnke, M. L., et al. (1991). J. Med.
Chem., 34, 2231.

144
N. R. Thimmegowda et al.
[4] Baraldi, P. G., Leoni, A., Cacciari, B., Manfredini, S., Simoni, D., Bergomi, M.,
Menta, E., & Spinelli, S. (1994). J. Med. Chem., 37, 4329.
[5] Razminia, M., Salem, Y., Devaki, S., Shah, N., & Khosla, S. (2006). Am. J. Ther., 13,
274.
[6] Wan, Y., Hur, W., Cho, C. Y., Liu, Y., Adrian, F. J., Lozach, O., Bach, S., Mayer, T.,
Fabbro, D., Meijer, L., & Gray, N. S. (2004). Chem. Biol., 11, 247.
[7] Stochla, K., Dorociak, A., & Makulska, H. E. (1984). Pol. J. Pharmacol Pharm., 36,
665.
[8] Thimmegowda, N. R., Dharmappa, K. K., Ananda Kumar, C. S., Sadashiva, M. P.,
Sathish, A. D., Nanda, B. L., Vishwanath, B. S., & Rangappa, K. S. (2007). Curr.
Top. Med. Chem., 7, 811.
[9] Otwinowski, Z., Minor, W., Carter, Jr., & Sweet, R. M. (1997). Methods in
Enzymology, 276, 307.
[10] Sheldrick, G. M. (1997). (SHELXS-97). University of Gottingen: Germany.
[11] Sheldrick, G. M. (1997). (SHELXL-97). University of Gottingen: Germany.