research communications
E)-2-{[(3-chlorophenyl)imino]methyl}-6-methylphenol
DFT and MEP study of (aOndokuz Mayıs University, Educational Faculty, Department of Mathematic and Science Education, 55139, Samsun, Turkey, bOndokuz Mayıs University, Faculty of Arts and Sciences, Department of Chemistry, 55139, Samsun, Turkey, cYeditepe University, Department of Chemical Engineering, 34755, Istanbul, Turkey, dOndokuz Mayıs University, Faculty of Arts and Sciences, Department of Physics, 55139, Samsun, Turkey, and eDepartment of Chemistry, Taras Shecchenko National University of Kyiv, 64, Vladimirska Str., Kiev 01601, Ukraine
*Correspondence e-mail: hanifesa@omu.edu.tr, tiskenderov@ukr.net
In the 14H12ClNO, the molecules are linked through C—H⋯O hydrogen bonds and C—H⋯π interactions, forming chains parallel to the [010] direction. π–π interactions and intramolecular hydrogen bonds are also observed. The molecular geometry of the title compound in the ground state has been calculated using density functional theory at the B3LYP level with the 6–311++G(2d,2p) basis set. Additionally, frontier molecular orbital and molecular electrostatic potential map analyses were performed.
of the title compound, CKeywords: energy gap; Schiff base; anti-bacterial agent; frontier molecular orbitals; crystal structure.
CCDC reference: 1974885
1. Chemical context
et al., 2009; Schiff, 1864). The presence of a lone pair of electrons in an sp2-hybridized orbital on the nitrogen atom of the azomethine group is of considerable chemical and biological importance (Sinha et al., 2008). In a continuation of our interest in the chemical, herbicidal and biological properties of we synthesized the title compound, (I), as a potential anti-bacterial agent (Yılmaz et al., 2012).
known as or have recently received considerable attention because of their good performance in coordination chemistry and anti-bacterial, anti-cancer and herbicidal applications (Piotr and quantum chemical computational studies of the Schiff base compound, (I)2. Structural commentary
The structure of the title compound (I) is shown in Fig. 1. It crystallizes in the orthorhombic Pbca with eight molecules in the The molecular structure has two planar rings. The whole molecule is approximately planar, with a maximum deviation of −0.0236 (12) Å from planarity for the C8 atom of Schiff base. The title compound displays an E configuration with respect to the C8=N double bond. The dihedral angle between the two phenyl ring planes is 0.34 (9)° and the C5—C8—N1—C9 torsion angle is −179.81 (15)°. The planar molecular conformation is stabilized by the intramolecular O1—H1⋯N1 hydrogen bond, which forms an S(6) motif.
3. Supramolecular features
In the crystal, the molecules are linked by C10—H10⋯O1 hydrogen bonds (Table 1), generating a C44(16) chain running parallel to the [010] direction (Fig. 2). C—H⋯π interactions occur between the two phenyl rings (Fig. 3, Table 1). π–π stacking interactions [centroid–centroid distance = 3.6389 (11) Å] between the chlorophenyl and methylphenol rings are also observed.
4. Database survey
A search of the Cambridge Structural Database (CSD, version 5.40; update Nov. 2018; Groom et al., 2016) gave eighteen hits for the (E)-2-{[(3-chlorophenyl)imino]methyl}-6-methylphenol structure. With a value of 1.271 (2) Å, the N1—C8 bond in the title compound (I) is the same length within standard uncertainties as those in the structures of 2-[(E)-(5-chloro-2-methylphenyl)iminomethyl]-4-methylphenol (AFILAE; Zheng, 2013b), 2,4-dibromo-6-{[(5-chloro-2-methylphenyl)imino]methyl}phenol (AGEGUQ; Zheng, 2013a), 2-[(E)-(2,4,6-trichlorophenyl)iminomethyl]phenol (AWUSIV; Fun et al., 2011), N-(2-methyl-5-chlorophenyl)salicylaldimine (BEYQEB; Elmalı & Elerman, 1998), (E)-2-[(3-chlorophenylimino)methyl]-4-methoxyphenol (DUBNAQ; Özek et al., 2009), 3-{(E)-[(3,4-dichlorophenyl)imino]methyl}benzene-1,2-diol (MOYHAL; Tahir et al., 2015) and N-(3-chlorophenyl)salicylaldimine (NADZUO; Karakaş et al., 2004) where the C=N bond length varies from 1.266 (4) to 1.290 (3) Å. These structures also have an intramolecular O1—H1⋯N1 hydrogen bond resulting in the formation of a six-membered ring and exhibit an E configuration.
5. Frontier molecular orbital analysis
The frontier molecular orbitals are important in the determination of the optical, electronic and anti-corrosion properties of a molecular system (Koepnick et al., 2010; Solomon et al., 2012; Jafari et al., 2013). A molecule with a small frontier orbital gap is more polarizable than one with a large gap and is considered a soft molecule because of its high chemical reactivity and low kinetic stability (Prabavathi et al., 2015). The energy levels of the HOMO (highest occupied molecular orbital), HOMO-1, LUMO (lowest occupied molecular orbital) and LUMO+1 orbitals calculated at the B3LYP/6-311++G(2d,2p) level (Frisch et al., 2009; Dennington et al., 2007) for (I) are shown in Fig. 4. The HOMO, HOMO-1 and LUMO orbitals are delocalized over the two phenyl rings connected by a Schiff base bridge and HOMO and HOMO-1 can be said to be π-bonding orbitals. The LUMO+1 orbitals are delocalized on the chlorophenyl ring and the C atom of the Schiff base. LUMO and LUMO+1 orbitals exhibit π* antibonding character. The energy gap of (I) is 4.069 eV. The other molecular orbital energies are shown in Fig. 4. (A) and (IP) can be defined as A = −ELUMO and IP = −EHOMO. Additionally, these values can also be used calculate the (χ), chemical hardness (η) and chemical softness (S) (Prabavathi et al., 2015; Karunakaran & Balachandran, 2014). For the title compound (I), A = 2.201 eV, IP = 6.270 eV, χ = 4.236 eV, η = 2.035 eV, and S = 0.246 eV.
6. Molecular electrostatic potential surface analysis
The analysis of a three-dimensional plot of the molecular electrostatic potential (MEP) surface is a technique for mapping the electrostatic potential onto the isoelectronic density surface, providing information about the reactive sites. The surface simultaneously displays molecular size and shape and the electrostatic potential value. In the colour scheme adopted, red indicates an electron-rich region with a partial negative charge and blue an electron-deficient region with partial positive charge, light blue indicates a slightly electron-deficient region, yellow a slightly electron-rich region and green a neutral region (Politzer et al., 2002). The MEP map of (I) was obtained by the B3LYP/6-311++G(2d,2p) method. In Fig. 5, it is shown that (I) has two possible sites of electrophilic attack. The negative region is localized on the protonated oxygen atom of methylphenol ring, O1, with a minimum value of −0.031 a.u. Positive potential sites of the compound are around hydrogen atoms. However, the maximum positive region is localized on the hydrogen atom bonded to the C atom forming the Schiff base, which can be considered as one possible site for nucleophilic attack, with a maximum value of 0.027 a.u.
7. Synthesis and crystallization
A mixture of 2-hydroxy-3-methylbenzaldehyde (34.0 mg, 0.25 mmol) and 4-chloroaniline (31.9 mg, 0.25 mmol) was stirred with ethanol (30 mL) at 377 K for 4 h, affording the title compound (43.0 mg, yield 70%, m.p. 362–364 K). Single crystals suitable for X-ray measurements were obtained by recrystallization from methanol at room temperature.
8. Refinement
Crystal data, data collection and structure . H atoms were placed in calculated positions and refined using a riding model with C—H = 0.93–0.96 Å, Uiso(H) = 1.2–1.5Ueq(C).
details are summarized in Table 2Supporting information
CCDC reference: 1974885
https://doi.org/10.1107/S2056989019017353/mw2154sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989019017353/mw2154Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989019017353/mw2154Isup3.cml
Data collection: X-AREA (Stoe & Cie, 2002); cell
X-AREA (Stoe & Cie, 2002); data reduction: X-RED32 (Stoe & Cie, 2002); program(s) used to solve structure: SHELXT2018 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: Mercury (Macrae et al., 2006), WinGX (Farrugia, 2012) and PLATON (Spek, 2009).C14H12ClNO | Dx = 1.337 Mg m−3 |
Mr = 245.70 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, Pbca | Cell parameters from 15471 reflections |
a = 14.0717 (8) Å | θ = 1.5–25.2° |
b = 6.4811 (4) Å | µ = 0.29 mm−1 |
c = 26.767 (2) Å | T = 296 K |
V = 2441.1 (3) Å3 | Prism, orange |
Z = 8 | 0.45 × 0.43 × 0.38 mm |
F(000) = 1024 |
Stoe IPDS 2 diffractometer | 2052 independent reflections |
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus | 1669 reflections with I > 2σ(I) |
Plane graphite monochromator | Rint = 0.033 |
Detector resolution: 6.67 pixels mm-1 | θmax = 24.6°, θmin = 1.5° |
rotation method scans | h = −16→16 |
Absorption correction: integration (X-RED32; Stoe & Cie, 2002) | k = −6→7 |
Tmin = 0.820, Tmax = 0.907 | l = −30→31 |
10011 measured reflections |
Refinement on F2 | Primary atom site location: other |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.039 | H-atom parameters constrained |
wR(F2) = 0.117 | w = 1/[σ2(Fo2) + (0.0666P)2 + 0.3364P] where P = (Fo2 + 2Fc2)/3 |
S = 1.05 | (Δ/σ)max < 0.001 |
2052 reflections | Δρmax = 0.16 e Å−3 |
155 parameters | Δρmin = −0.24 e Å−3 |
0 restraints |
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. |
x | y | z | Uiso*/Ueq | ||
Cl1 | 0.33517 (5) | 0.79127 (10) | 0.03649 (2) | 0.0888 (3) | |
C12 | 0.32979 (13) | 0.7525 (3) | 0.13616 (8) | 0.0632 (5) | |
H12 | 0.296569 | 0.876559 | 0.136229 | 0.076* | |
C13 | 0.35979 (13) | 0.6646 (3) | 0.09213 (7) | 0.0565 (5) | |
C11 | 0.35033 (14) | 0.6518 (3) | 0.18009 (8) | 0.0655 (5) | |
H11 | 0.330163 | 0.707801 | 0.210266 | 0.079* | |
C14 | 0.40948 (13) | 0.4816 (3) | 0.09088 (7) | 0.0554 (5) | |
H14 | 0.428370 | 0.425004 | 0.060536 | 0.067* | |
C9 | 0.43105 (12) | 0.3826 (3) | 0.13554 (6) | 0.0501 (4) | |
C10 | 0.40037 (13) | 0.4690 (3) | 0.18002 (7) | 0.0581 (5) | |
H10 | 0.413635 | 0.403110 | 0.210087 | 0.070* | |
C8 | 0.51952 (12) | 0.1055 (3) | 0.10169 (7) | 0.0533 (4) | |
H8 | 0.511386 | 0.163728 | 0.070226 | 0.064* | |
N1 | 0.48348 (10) | 0.1964 (2) | 0.13929 (5) | 0.0524 (4) | |
C4 | 0.60571 (14) | −0.1837 (3) | 0.06298 (7) | 0.0617 (5) | |
H4 | 0.594284 | −0.124767 | 0.031869 | 0.074* | |
C5 | 0.57270 (12) | −0.0849 (3) | 0.10589 (6) | 0.0507 (4) | |
C3 | 0.65470 (14) | −0.3660 (3) | 0.06587 (8) | 0.0658 (5) | |
H3 | 0.676683 | −0.430204 | 0.037024 | 0.079* | |
C6 | 0.59085 (12) | −0.1759 (3) | 0.15252 (6) | 0.0511 (4) | |
O1 | 0.56117 (10) | −0.0861 (2) | 0.19521 (4) | 0.0668 (4) | |
H1 | 0.533250 | 0.021525 | 0.188623 | 0.100* | |
C2 | 0.67106 (13) | −0.4535 (3) | 0.11231 (8) | 0.0631 (5) | |
H2 | 0.703893 | −0.577825 | 0.114078 | 0.076* | |
C1 | 0.64031 (13) | −0.3625 (3) | 0.15602 (7) | 0.0563 (5) | |
C7 | 0.65775 (16) | −0.4616 (4) | 0.20614 (9) | 0.0763 (6) | |
H7A | 0.694377 | −0.585261 | 0.201724 | 0.114* | |
H7B | 0.598004 | −0.495240 | 0.221426 | 0.114* | |
H7C | 0.691973 | −0.367515 | 0.227197 | 0.114* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cl1 | 0.1145 (5) | 0.0730 (4) | 0.0790 (4) | 0.0241 (3) | −0.0112 (3) | 0.0176 (3) |
C12 | 0.0587 (11) | 0.0503 (11) | 0.0807 (15) | 0.0027 (9) | 0.0037 (9) | −0.0065 (10) |
C13 | 0.0583 (10) | 0.0475 (11) | 0.0637 (11) | 0.0008 (8) | −0.0049 (8) | 0.0044 (9) |
C11 | 0.0684 (12) | 0.0645 (13) | 0.0635 (12) | 0.0014 (10) | 0.0096 (9) | −0.0150 (10) |
C14 | 0.0651 (11) | 0.0511 (11) | 0.0502 (10) | 0.0032 (9) | −0.0001 (8) | 0.0002 (8) |
C9 | 0.0527 (9) | 0.0450 (10) | 0.0526 (9) | −0.0037 (8) | −0.0025 (7) | 0.0014 (8) |
C10 | 0.0644 (11) | 0.0594 (12) | 0.0506 (10) | −0.0040 (9) | 0.0028 (8) | −0.0030 (9) |
C8 | 0.0620 (11) | 0.0483 (10) | 0.0498 (9) | −0.0007 (8) | −0.0023 (8) | 0.0062 (8) |
N1 | 0.0595 (9) | 0.0461 (9) | 0.0517 (8) | 0.0007 (7) | −0.0021 (6) | 0.0006 (7) |
C4 | 0.0693 (11) | 0.0610 (13) | 0.0546 (11) | 0.0007 (10) | 0.0075 (9) | 0.0022 (9) |
C5 | 0.0545 (9) | 0.0454 (10) | 0.0520 (10) | −0.0020 (8) | 0.0018 (7) | 0.0011 (8) |
C3 | 0.0676 (12) | 0.0597 (12) | 0.0702 (13) | 0.0030 (10) | 0.0129 (9) | −0.0078 (10) |
C6 | 0.0532 (9) | 0.0483 (11) | 0.0518 (10) | −0.0016 (8) | −0.0018 (7) | 0.0006 (8) |
O1 | 0.0889 (10) | 0.0615 (9) | 0.0500 (7) | 0.0148 (7) | −0.0033 (6) | 0.0003 (6) |
C2 | 0.0545 (10) | 0.0492 (11) | 0.0854 (14) | 0.0022 (8) | 0.0064 (9) | 0.0017 (10) |
C1 | 0.0521 (9) | 0.0512 (11) | 0.0655 (11) | −0.0010 (8) | −0.0028 (8) | 0.0064 (9) |
C7 | 0.0836 (15) | 0.0674 (14) | 0.0779 (14) | 0.0115 (11) | −0.0107 (11) | 0.0173 (11) |
Cl1—C13 | 1.7357 (19) | C4—C3 | 1.370 (3) |
C12—C13 | 1.375 (3) | C4—C5 | 1.395 (2) |
C12—C11 | 1.376 (3) | C4—H4 | 0.9300 |
C12—H12 | 0.9300 | C5—C6 | 1.404 (2) |
C13—C14 | 1.377 (3) | C3—C2 | 1.386 (3) |
C11—C10 | 1.378 (3) | C3—H3 | 0.9300 |
C11—H11 | 0.9300 | C6—O1 | 1.348 (2) |
C14—C9 | 1.390 (2) | C6—C1 | 1.399 (3) |
C14—H14 | 0.9300 | O1—H1 | 0.8200 |
C9—C10 | 1.385 (2) | C2—C1 | 1.380 (3) |
C9—N1 | 1.418 (2) | C2—H2 | 0.9300 |
C10—H10 | 0.9300 | C1—C7 | 1.507 (3) |
C8—N1 | 1.271 (2) | C7—H7A | 0.9600 |
C8—C5 | 1.448 (2) | C7—H7B | 0.9600 |
C8—H8 | 0.9300 | C7—H7C | 0.9600 |
C13—C12—C11 | 118.11 (18) | C5—C4—H4 | 119.4 |
C13—C12—H12 | 120.9 | C4—C5—C6 | 118.61 (16) |
C11—C12—H12 | 120.9 | C4—C5—C8 | 119.96 (16) |
C12—C13—C14 | 122.25 (18) | C6—C5—C8 | 121.42 (16) |
C12—C13—Cl1 | 118.56 (15) | C4—C3—C2 | 119.16 (19) |
C14—C13—Cl1 | 119.19 (15) | C4—C3—H3 | 120.4 |
C12—C11—C10 | 120.94 (18) | C2—C3—H3 | 120.4 |
C12—C11—H11 | 119.5 | O1—C6—C1 | 118.05 (15) |
C10—C11—H11 | 119.5 | O1—C6—C5 | 121.05 (16) |
C13—C14—C9 | 119.17 (17) | C1—C6—C5 | 120.90 (16) |
C13—C14—H14 | 120.4 | C6—O1—H1 | 109.5 |
C9—C14—H14 | 120.4 | C1—C2—C3 | 122.26 (18) |
C10—C9—C14 | 118.98 (17) | C1—C2—H2 | 118.9 |
C10—C9—N1 | 116.45 (16) | C3—C2—H2 | 118.9 |
C14—C9—N1 | 124.57 (16) | C2—C1—C6 | 117.95 (17) |
C11—C10—C9 | 120.54 (18) | C2—C1—C7 | 121.44 (18) |
C11—C10—H10 | 119.7 | C6—C1—C7 | 120.61 (17) |
C9—C10—H10 | 119.7 | C1—C7—H7A | 109.5 |
N1—C8—C5 | 122.65 (16) | C1—C7—H7B | 109.5 |
N1—C8—H8 | 118.7 | H7A—C7—H7B | 109.5 |
C5—C8—H8 | 118.7 | C1—C7—H7C | 109.5 |
C8—N1—C9 | 123.07 (15) | H7A—C7—H7C | 109.5 |
C3—C4—C5 | 121.12 (18) | H7B—C7—H7C | 109.5 |
C3—C4—H4 | 119.4 | ||
C11—C12—C13—C14 | −0.3 (3) | N1—C8—C5—C4 | 176.22 (18) |
C11—C12—C13—Cl1 | −179.48 (15) | N1—C8—C5—C6 | −2.7 (3) |
C13—C12—C11—C10 | 0.6 (3) | C5—C4—C3—C2 | 0.3 (3) |
C12—C13—C14—C9 | −0.6 (3) | C4—C5—C6—O1 | 179.49 (16) |
Cl1—C13—C14—C9 | 178.56 (14) | C8—C5—C6—O1 | −1.6 (3) |
C13—C14—C9—C10 | 1.2 (3) | C4—C5—C6—C1 | −0.5 (3) |
C13—C14—C9—N1 | −178.54 (16) | C8—C5—C6—C1 | 178.43 (16) |
C12—C11—C10—C9 | −0.1 (3) | C4—C3—C2—C1 | −0.5 (3) |
C14—C9—C10—C11 | −0.9 (3) | C3—C2—C1—C6 | 0.2 (3) |
N1—C9—C10—C11 | 178.88 (16) | C3—C2—C1—C7 | 179.21 (19) |
C5—C8—N1—C9 | −179.81 (15) | O1—C6—C1—C2 | −179.65 (16) |
C10—C9—N1—C8 | −176.76 (17) | C5—C6—C1—C2 | 0.3 (3) |
C14—C9—N1—C8 | 3.0 (3) | O1—C6—C1—C7 | 1.3 (3) |
C3—C4—C5—C6 | 0.2 (3) | C5—C6—C1—C7 | −178.70 (17) |
C3—C4—C5—C8 | −178.79 (17) |
Cg1 and Cg are the centroids of the C1–C6 and C9–C14 rings, respectively. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···N1 | 0.82 | 1.88 | 2.605 (2) | 148 |
C10—H10···O1i | 0.93 | 2.56 | 3.402 (2) | 151 |
C2—H2···Cg1ii | 0.93 | 2.75 | 3.561 (2) | 147 |
C12—H12···Cg2iii | 0.93 | 2.78 | 3.589 (2) | 147 |
Symmetry codes: (i) −x+1, y+1/2, −z+1/2; (ii) −x+3/2, y−1/2, z; (iii) −x+1/2, y+1/2, z. |
Funding information
Funding for this research was provided by: Ondokuz Mayıs University (award No. PYO.FEN.1906.19.001).
References
Dennington, R. I. I., Keith, T. & Millam, J. (2007). GaussView. Version 4.1.2. Semichem Inc., Shawnee Mission, KS, USA. Google Scholar
Elmalı, A. & Elerman, Y. (1998). J. Mol. Struct. 442, 31–37. Web of Science CSD CrossRef CAS Google Scholar
Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Web of Science CrossRef CAS IUCr Journals Google Scholar
Frisch, M. J., et al. (2009). GAUSSIAN09. Gaussian Inc., Wallingford, CT, USA. Google Scholar
Fun, H.-K., Quah, C. K., Viveka, S., Madhukumar, D. J. & Nagaraja, G. K. (2011). Acta Cryst. E67, o1934. Web of Science CSD CrossRef IUCr Journals Google Scholar
Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171–179. Web of Science CrossRef IUCr Journals Google Scholar
Jafari, H., Danaee, I., Eskandari, H. & RashvandAvei, M. (2013). Ind. Eng. Chem. Res. 52, 6617–6632. Web of Science CrossRef CAS Google Scholar
Karakaş, A., Elmali, A., Ünver, H. & Svoboda, I. (2004). J. Mol. Struct. 702, 103–110. Google Scholar
Karunakaran, V. & Balachandran, V. (2014). Spectrochim. Acta A Mol. Biomol. Spectrosc. 128, 1–14. Web of Science CrossRef CAS PubMed Google Scholar
Koepnick, B. D., Lipscomb, J. S. & Taylor, D. K. (2010). J. Phys. Chem. A, 114, 13228–13233. Web of Science CrossRef CAS PubMed Google Scholar
Macrae, C. F., Edgington, P. R., McCabe, P., Pidcock, E., Shields, G. P., Taylor, R., Towler, M. & van de Streek, J. (2006). J. Appl. Cryst. 39, 453–457. Web of Science CrossRef CAS IUCr Journals Google Scholar
Özek, A., Albayrak, Ç., Odabaşoğlu, M. & Büyükgüngör, O. (2009). J. Chem. Crystallogr. 39, 353–357. Google Scholar
Politzer, P. & Murray, J. S. (2002). Theor. Chimi. Acta, 108, 134–142. Web of Science CrossRef CAS Google Scholar
Prabavathi, N., Senthil, N. N. & Krishnakumar, V. (2015). Pharm Anal Acta 6, 1–20. Google Scholar
Przybylski, P., Huczynski, A., Pyta, K., Brzezinski, B. & Bartl, F. (2009). Curr. Org. Chem. 13, 124–148. Web of Science CrossRef CAS Google Scholar
Schiff, H. (1864). Ann. Chem. Suppl, 3, 343–349. Google Scholar
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sinha, D., Tiwari, A. K., Singh, S., Shukla, G., Mishra, P., Chandra, H. & Mishra, A. K. (2008). Eur. J. Med. Chem. 43, 160–165. Web of Science CrossRef PubMed CAS Google Scholar
Solomon, R. V., Bella, A. P., Vedha, S. A. & Venuvanalingam, P. (2012). Phys. Chem. Chem. Phys. PCCP, 14, 14229–14237. Web of Science CrossRef PubMed Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Stoe & Cie (2002). X-AREA and X-RED32. Stoe & Cie GmbH, Darmstadt, Germany. Google Scholar
Tahir, M. N., Shad, H. A., Rauf, A. & Khan, A. H. (2015). Acta Cryst. E71, o137–o138. Web of Science CSD CrossRef IUCr Journals Google Scholar
Yılmaz, I., Kazak, C., Gümüş, S., Ağar, E. & Ardalı, Y. (2012). Spectrochim. Acta A Mol. Biomol. Spectrosc. 97, 423–428. Web of Science PubMed Google Scholar
Zheng, Y. (2013a). Acta Cryst. E69, o1190. CSD CrossRef IUCr Journals Google Scholar
Zheng, Y.-F. (2013b). Acta Cryst. E69, o1349. CSD CrossRef 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.