research communications
E)-4-bromo-N′-(2,3-dichlorobenzylidene)benzohydrazide
Hirshfeld surface analysis and frontier molecular orbital analysis of (aDepartment of Chemistry, Government Arts College (Autonomous), Thanthonimalai, Karur- 639 005, Tamil Nadu, India
*Correspondence e-mail: manavaibala@gmail.com
The title Schiff base compound, C14H9BrCl2N2O, displays a trans or E configuration with respect to the C=N bond, with a dihedral angle 15.7 (2)° formed between the benzene rings. In the crystal, molecules are linked by N—H⋯O and C—H⋯O hydrogen bonds, forming chains along [001] which enclose R12(6) loops. The intermolecular interactions were investigated by Hirshfeld surfaces analysis and two-dimensional fingerprint plots. The DFT-B3LYP/6–311 G++(d,p) method was used to determine the HOMO–LUMO energy levels.
CCDC reference: 1587252
1. Chemical context
). A wide range of these compounds, with the general formula RHC=NR1 (R and R1 can be alkyl, aryl, cycloalkyl or heterocyclic groups) have been synthesized. They are of great importance in the field of coordination chemistry as they are able to form stable complexes with many metal ions (Souza et al., 1985). The chemical and biological significance of can be attributed to the presence of a in the sp2-hybridized orbital of the nitrogen atom of the azomethine group (Singh et al., 1975). These compounds are used in the fields of organic synthesis, chemical catalysis, medicine and pharmacy as well as other new technologies (Tanaka et al., 2010). are also used as probes in investigating the structure of DNA (Tiwari et al., 2011) and have gained special attention in pharmacophore research and in the development of several bioactive lead molecules (Muralisankar et al., 2016). They also exhibit photochromic and thermochromic properties and have been used in information storage, electronic display systems, optical switching devices, and ophthalmic glasses (Amimoto & Kawato, 2005). Herein, we report on the the Hirshfeld surface analysis and the molecular orbital analysis of the title compound, (E)-4-bromo-N′-(2,3-dichlorobenzylidene)benzohydrazide.
are nitrogen-containing compounds that were first obtained by the condensation reactions of aromatic and (Schiff, 18642. Structural commentary
The molecular structure of the title compound is illustrated in Fig. 1. The configuration about the C8=N2 bond, which has a bond length of 1.271 (5) Å, is E. The benzene rings (C1–C6 and C9–C14) are inclined to each other by 15.7 (2)°. The bond lengths and angles and the overall conformation of the molecule are close to those reported for a very similar compound, (E)-4-bromo-N′-(2-chlorobenzylidene)benzohydrazide (Shu et al., 2009).
3. Supramolecular features
In the crystal, molecules are linked by N—H⋯O and C—H⋯O hydrogen bonds, forming chains that propagate along the [001] direction and which enclose (6) ring motifs (Fig. 2 and Table 1). Here the oxygen atom O1 acts as a bifurcated acceptor. There are no other significant intermolecular interactions present (see Table 2 in Hirshfeld surface analysis).
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4. Hirshfeld surface analysis
Crystal Explorer (Wolff et al., 2012) was used to generate the Hirshfeld surface and two-dimensional fingerprint plots (Rohl et al., 2008). The three-dimensional dnorm surface is a useful tool for analysing and visualizing the intermolecular interactions, which are given in Table 2. The dnorm values are negative or positive depending on whether the intermolecular contact is shorter or longer than the sum of the van der Waals radii (Spackman & Jayatilaka, 2009; McKinnon et al., 2007). The total dnorm surface of the title compound is shown in Fig. 3. The red spots correspond to the N—H⋯O and C—H⋯O interactions, the most significant interactions in the crystal (Tables 1 and 2).
The two-dimensional fingerprint plots from the Hirshfeld surface analysis are shown in Fig. 4. They indicate the percentage contributions of the various intermolecular contacts to the Hirshfeld surface, the most significant are Cl⋯H/H⋯Cl (22.5%), H⋯H (15.7%), C⋯H/H⋯C (13.2%), Br⋯H/H⋯Br (11.5%), C⋯C (9.8%), O⋯H/H⋯O (9.0%), N⋯H/H⋯N (4.9%), and Br⋯Cl/Cl⋯Br (3.3%), as shown in Fig. 4, cf Table 2.
5. Frontier molecular orbital calculations
The HOMO (highest occupied molecular orbital) acts as an et al., 2017). The energy gap between HOMO–LUMO orbitals, which determines the chemical stability, chemical hardness, and the index are shown in Fig. 5 and details are given in Table 3. The frontier molecular orbital LUMO is located over the whole of the molecule. The energy gap of the molecule clearly shows the charge-transfer interaction involving donor and acceptor groups. The chemical hardness and softness of a molecule is a sign of its chemical stability. From the HOMO–LUMO energy gap, we can see whether or not the molecule is hard or soft. If the energy gap is large, the molecule is hard and if small the molecule is soft. Soft molecules are more polarizable than hard ones because they need less energy for excitation. From the data presented in Table 3, we conclude that the energy gap is large, hence the title molecule is a hard material and will be difficult to polarize.
and the LUMO (lowest occupied molecular orbital) as an If the energy gap is small then the molecule is highly polarizable and has high chemical reactivity. The energy levels of the title compound were computed using the DFT-B3LYP/6-311G++(d,p) method (Sivajeyanthi
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6. Database survey
A search of the Cambridge Structural Database (CSD, version 5.39, last update August 2018; Groom et al., 2016) for 4-bromo-(benzylidene)benzohydrazides yielded six structures. They include the following analogues: 2,4-dihydroxybenzylidene [ATOSEJ (Mohanraj et al., 2016) and ATOSEJ01 (Arunagiri et al., 2018)], 2-nitrobenzylidene (EGUSEF; Zhang et al., 2009), 2-chlorobenzylidene (HOTDAW; Shu et al., 2009), 2-hydroxy-1-naphthylmethylene (IFUSEI; Diao et al., 2008), 2-hydroxy-5-methoxybenzylidene (OBUBUL; Wang et al., 2017) and 4-hydroxy-3-methoxybenzylidene (YAWXOL; Horkaew et al., 2012). They all have an E configuration about the C=N bond. The N—N bond lengths vary from 1.366 (4) to 1.396 (5) Å while the C=N bond lengths vary from 1.264 (4) to 1.285 (2) Å. The values observed for the title compound, respectively, 1.391 (4) and 1.271 (5) Å, fall within these limits. The dihedral angle between the two benzene rings varies from as little as 4.12 (17)° in EGUSEF to 49.08 (18)° in ATOSEJ01. In the title compound this dihedral angle is 15.7 (2)°, similar to the values observed for HOTDAW, the 2-chlorobenzylidene analogue, and for YAWXOL, the 4-hydroxy-3-methoxybenzylidene analogue, for which the dihedral angles are 11.43 (16) and 13.92 (6)°, respectively.
7. Synthesis and crystallization
The title compound was synthesized by the reaction of 1:1 molar ratio mixture of a hot ethanolic solution (20 ml) of 4-bromobenzohydrazide (0.213 mg, Aldrich) and 2,3-dichlorobenzaldehyde (0.175 mg, Aldrich), which was refluxed for 8 h. The solution was then cooled and kept at room temperature. The powder obtained was recrystallized from dimethyl sulfoxide (DMSO). Colourless block-like crystals suitable for the X-ray
were obtained in a few days.8. Refinement
Crystal data, data collection and structure . The hydrogen atoms were positioned geometrically and refined using a riding model: C—H = 0.93 Å, N—H = 0.86 Å, with Uiso(H) = 1.2Ueq(N, C).
details are summarized in Table 4Supporting information
CCDC reference: 1587252
https://doi.org/10.1107/S2056989019001816/su5466sup1.cif
contains datablocks global, I, 1. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989019001816/su5466Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989019001816/su5466Isup3.cml
Data collection: APEX2 (Bruker, 2004); cell
APEX2 and SAINT (Bruker, 2004); data reduction: SAINT and XPREP (Bruker, 2004); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL2017 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL2017 (Sheldrick, 2015) and PLATON (Spek, 2009).C14H9BrCl2N2O | F(000) = 736 |
Mr = 372.04 | Dx = 1.699 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 11.1952 (18) Å | Cell parameters from 3186 reflections |
b = 14.055 (2) Å | θ = 4.7–47.5° |
c = 9.3050 (12) Å | µ = 3.19 mm−1 |
β = 96.446 (6)° | T = 296 K |
V = 1454.8 (4) Å3 | Block, colourless |
Z = 4 | 0.30 × 0.20 × 0.20 mm |
Bruker Kappa APEXII CCD diffractometer | 1724 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.050 |
ω and φ scan | θmax = 28.3°, θmin = 2.6° |
Absorption correction: multi-scan (SADABS; Bruker, 2004) | h = −14→14 |
Tmin = 0.448, Tmax = 0.568 | k = −18→18 |
11392 measured reflections | l = −8→12 |
3363 independent reflections |
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)] = 0.051 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.173 | H-atom parameters constrained |
S = 0.94 | w = 1/[σ2(Fo2) + (0.1P)2] where P = (Fo2 + 2Fc2)/3 |
3363 reflections | (Δ/σ)max < 0.001 |
181 parameters | Δρmax = 0.70 e Å−3 |
0 restraints | Δρmin = −0.63 e Å−3 |
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. |
x | y | z | Uiso*/Ueq | ||
Br1 | 0.45376 (6) | −0.17154 (4) | 0.33892 (7) | 0.0891 (3) | |
Cl1 | 0.24263 (13) | 0.60728 (9) | 0.12531 (12) | 0.0749 (4) | |
Cl2 | 0.11288 (14) | 0.77291 (9) | −0.05544 (15) | 0.0843 (5) | |
O1 | 0.2713 (3) | 0.1659 (2) | −0.1706 (3) | 0.0628 (9) | |
N1 | 0.2462 (3) | 0.2532 (2) | 0.0288 (3) | 0.0456 (9) | |
H1N1 | 0.253851 | 0.257938 | 0.121571 | 0.055* | |
N2 | 0.1988 (3) | 0.3275 (2) | −0.0585 (4) | 0.0478 (9) | |
C6 | 0.3268 (4) | 0.0931 (3) | 0.0576 (4) | 0.0439 (10) | |
C9 | 0.1358 (4) | 0.4878 (3) | −0.0799 (4) | 0.0470 (10) | |
C7 | 0.2801 (4) | 0.1731 (3) | −0.0370 (4) | 0.0452 (10) | |
C5 | 0.3717 (4) | 0.1033 (3) | 0.2017 (4) | 0.0473 (10) | |
H5 | 0.375456 | 0.163419 | 0.243713 | 0.057* | |
C10 | 0.1524 (4) | 0.5818 (3) | −0.0321 (4) | 0.0483 (10) | |
C3 | 0.4067 (4) | −0.0633 (3) | 0.2236 (5) | 0.0527 (11) | |
C4 | 0.4112 (4) | 0.0249 (3) | 0.2838 (5) | 0.0539 (11) | |
H4 | 0.440892 | 0.032600 | 0.380460 | 0.065* | |
C8 | 0.1896 (4) | 0.4073 (3) | 0.0037 (4) | 0.0496 (11) | |
H8 | 0.216763 | 0.414398 | 0.101258 | 0.060* | |
C11 | 0.0950 (5) | 0.6564 (3) | −0.1127 (5) | 0.0569 (12) | |
C12 | 0.0226 (5) | 0.6387 (4) | −0.2402 (5) | 0.0663 (14) | |
H12 | −0.015996 | 0.688339 | −0.292702 | 0.080* | |
C14 | 0.0639 (4) | 0.4716 (3) | −0.2103 (5) | 0.0555 (12) | |
H14 | 0.053241 | 0.409731 | −0.244882 | 0.067* | |
C1 | 0.3261 (5) | 0.0017 (3) | −0.0023 (5) | 0.0636 (13) | |
H1 | 0.299196 | −0.006402 | −0.099732 | 0.076* | |
C13 | 0.0084 (5) | 0.5456 (4) | −0.2885 (5) | 0.0674 (14) | |
H13 | −0.039161 | 0.533003 | −0.374844 | 0.081* | |
C2 | 0.3643 (5) | −0.0761 (3) | 0.0792 (6) | 0.0716 (15) | |
H2 | 0.361649 | −0.136545 | 0.038188 | 0.086* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Br1 | 0.0922 (5) | 0.0604 (4) | 0.1158 (6) | 0.0313 (3) | 0.0164 (4) | 0.0248 (3) |
Cl1 | 0.1014 (11) | 0.0608 (7) | 0.0589 (8) | −0.0126 (7) | −0.0069 (7) | 0.0007 (6) |
Cl2 | 0.1127 (13) | 0.0482 (7) | 0.0933 (10) | 0.0101 (7) | 0.0175 (9) | 0.0065 (6) |
O1 | 0.094 (3) | 0.0564 (19) | 0.0371 (17) | −0.0015 (16) | 0.0027 (16) | −0.0063 (13) |
N1 | 0.062 (2) | 0.0421 (19) | 0.0319 (17) | −0.0021 (17) | 0.0032 (16) | 0.0005 (14) |
N2 | 0.052 (2) | 0.047 (2) | 0.0430 (19) | −0.0024 (17) | 0.0010 (17) | 0.0065 (16) |
C6 | 0.042 (3) | 0.042 (2) | 0.048 (2) | −0.0064 (19) | 0.0082 (19) | −0.0053 (18) |
C9 | 0.044 (3) | 0.052 (2) | 0.047 (2) | −0.001 (2) | 0.012 (2) | 0.0049 (19) |
C7 | 0.049 (3) | 0.046 (2) | 0.041 (2) | −0.0128 (19) | 0.004 (2) | −0.0007 (19) |
C5 | 0.060 (3) | 0.040 (2) | 0.041 (2) | −0.003 (2) | 0.005 (2) | −0.0070 (17) |
C10 | 0.050 (3) | 0.052 (2) | 0.044 (2) | −0.003 (2) | 0.013 (2) | 0.0009 (18) |
C3 | 0.041 (3) | 0.052 (2) | 0.066 (3) | 0.013 (2) | 0.013 (2) | 0.008 (2) |
C4 | 0.061 (3) | 0.050 (2) | 0.050 (2) | 0.009 (2) | 0.004 (2) | 0.002 (2) |
C8 | 0.059 (3) | 0.047 (2) | 0.043 (2) | −0.004 (2) | 0.007 (2) | 0.0023 (19) |
C11 | 0.062 (3) | 0.053 (3) | 0.060 (3) | 0.003 (2) | 0.025 (3) | 0.010 (2) |
C12 | 0.068 (4) | 0.069 (3) | 0.062 (3) | 0.017 (3) | 0.005 (3) | 0.019 (3) |
C14 | 0.058 (3) | 0.061 (3) | 0.047 (3) | 0.006 (2) | 0.004 (2) | −0.002 (2) |
C1 | 0.085 (4) | 0.051 (3) | 0.051 (3) | 0.000 (3) | −0.008 (2) | −0.018 (2) |
C13 | 0.069 (4) | 0.078 (4) | 0.053 (3) | 0.012 (3) | −0.004 (3) | 0.002 (3) |
C2 | 0.076 (4) | 0.043 (3) | 0.093 (4) | 0.006 (2) | −0.004 (3) | −0.017 (3) |
Br1—C3 | 1.901 (4) | C5—H5 | 0.9300 |
Cl1—C10 | 1.721 (4) | C10—C11 | 1.402 (6) |
Cl2—C11 | 1.727 (5) | C3—C4 | 1.359 (6) |
O1—C7 | 1.240 (5) | C3—C2 | 1.385 (6) |
N1—C7 | 1.356 (5) | C4—H4 | 0.9300 |
N1—N2 | 1.391 (4) | C8—H8 | 0.9300 |
N1—H1N1 | 0.8600 | C11—C12 | 1.383 (7) |
N2—C8 | 1.271 (5) | C12—C13 | 1.386 (7) |
C6—C5 | 1.385 (5) | C12—H12 | 0.9300 |
C6—C1 | 1.400 (5) | C14—C13 | 1.377 (6) |
C6—C7 | 1.486 (6) | C14—H14 | 0.9300 |
C9—C14 | 1.398 (6) | C1—C2 | 1.372 (7) |
C9—C10 | 1.400 (6) | C1—H1 | 0.9300 |
C9—C8 | 1.464 (6) | C13—H13 | 0.9300 |
C5—C4 | 1.385 (6) | C2—H2 | 0.9300 |
C7—N1—N2 | 117.8 (3) | C3—C4—H4 | 119.9 |
C7—N1—H1N1 | 121.1 | C5—C4—H4 | 119.9 |
N2—N1—H1N1 | 121.1 | N2—C8—C9 | 119.3 (4) |
C8—N2—N1 | 116.2 (3) | N2—C8—H8 | 120.3 |
C5—C6—C1 | 117.7 (4) | C9—C8—H8 | 120.3 |
C5—C6—C7 | 124.1 (4) | C12—C11—C10 | 120.9 (4) |
C1—C6—C7 | 118.2 (4) | C12—C11—Cl2 | 118.2 (4) |
C14—C9—C10 | 118.2 (4) | C10—C11—Cl2 | 121.0 (4) |
C14—C9—C8 | 119.9 (4) | C11—C12—C13 | 118.9 (4) |
C10—C9—C8 | 121.9 (4) | C11—C12—H12 | 120.6 |
O1—C7—N1 | 121.7 (4) | C13—C12—H12 | 120.6 |
O1—C7—C6 | 121.0 (4) | C13—C14—C9 | 121.2 (4) |
N1—C7—C6 | 117.3 (3) | C13—C14—H14 | 119.4 |
C4—C5—C6 | 120.7 (4) | C9—C14—H14 | 119.4 |
C4—C5—H5 | 119.7 | C2—C1—C6 | 121.6 (4) |
C6—C5—H5 | 119.7 | C2—C1—H1 | 119.2 |
C9—C10—C11 | 120.0 (4) | C6—C1—H1 | 119.2 |
C9—C10—Cl1 | 120.7 (3) | C14—C13—C12 | 120.9 (5) |
C11—C10—Cl1 | 119.3 (3) | C14—C13—H13 | 119.6 |
C4—C3—C2 | 120.7 (4) | C12—C13—H13 | 119.6 |
C4—C3—Br1 | 120.1 (3) | C1—C2—C3 | 118.9 (4) |
C2—C3—Br1 | 119.1 (3) | C1—C2—H2 | 120.5 |
C3—C4—C5 | 120.3 (4) | C3—C2—H2 | 120.5 |
C7—N1—N2—C8 | −166.9 (4) | C14—C9—C8—N2 | 19.2 (6) |
N2—N1—C7—O1 | 1.1 (6) | C10—C9—C8—N2 | −162.0 (4) |
N2—N1—C7—C6 | −178.0 (4) | C9—C10—C11—C12 | −0.6 (7) |
C5—C6—C7—O1 | 160.5 (4) | Cl1—C10—C11—C12 | 179.5 (4) |
C1—C6—C7—O1 | −19.2 (6) | C9—C10—C11—Cl2 | 179.5 (3) |
C5—C6—C7—N1 | −20.4 (6) | Cl1—C10—C11—Cl2 | −0.4 (5) |
C1—C6—C7—N1 | 160.0 (4) | C10—C11—C12—C13 | −0.7 (7) |
C1—C6—C5—C4 | −1.8 (6) | Cl2—C11—C12—C13 | 179.2 (4) |
C7—C6—C5—C4 | 178.5 (4) | C10—C9—C14—C13 | −1.4 (7) |
C14—C9—C10—C11 | 1.6 (6) | C8—C9—C14—C13 | 177.5 (4) |
C8—C9—C10—C11 | −177.3 (4) | C5—C6—C1—C2 | 2.4 (7) |
C14—C9—C10—Cl1 | −178.5 (3) | C7—C6—C1—C2 | −177.9 (4) |
C8—C9—C10—Cl1 | 2.6 (6) | C9—C14—C13—C12 | 0.1 (7) |
C2—C3—C4—C5 | 0.9 (7) | C11—C12—C13—C14 | 0.9 (8) |
Br1—C3—C4—C5 | −177.0 (3) | C6—C1—C2—C3 | −1.4 (8) |
C6—C5—C4—C3 | 0.3 (7) | C4—C3—C2—C1 | −0.3 (7) |
N1—N2—C8—C9 | −177.5 (3) | Br1—C3—C2—C1 | 177.6 (4) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N1···O1i | 0.86 | 2.20 | 3.003 (4) | 155 |
C8—H8···O1i | 0.93 | 2.42 | 3.234 (5) | 146 |
Symmetry code: (i) x, −y+1/2, z+1/2. |
Atom1···Atom2 | Length | Length - vdW radii | Symm. op. 2 |
H1N1···H5 | 2.136 | -0.264 | x, y, z |
O1···H1N1 | 2.200 | -0.520 | x, 1/2 - y, z - 1/2 |
H1N1···H8 | 2.242 | -0.158 | x, y, z |
O1···H8 | 2.421 | -0.299 | x, 1/2 - y, z - 1/2 |
O1···H1 | 2.520 | -0.200 | x, y, z |
N2···H14 | 2.523 | -0.227 | x, y, z |
H1N1···C5 | 2.608 | -0.292 | x, y, z |
N1···H5 | 2.652 | -0.098 | x, y, z |
Cl1···H8 | 2.733 | -0.217 | x, y, z |
H1···Cl1 | 2.931 | -0.019 | x, 1/2 - y, z - 1/2 |
O1···N1 | 3.003 (4) | -0.067 | x, 1/2 - y, z - 1/2 |
H12···Cl2 | 3.024 | 0.074 | x, 3/2 - y, z - 1/2 |
O1···C8 | 3.234 (5) | 0.014 | x, 1/2 - y, z - 1/2 |
N2···C5 | 3.262 (5) | 0.012 | x, 1/2 - y, z - 1/2 |
C12···Cl2 | 3.440 (5) | -0.010 | x, 3/2 - y, z - 1/2 |
C9···C4 | 3.468 (6) | 0.068 | x, 1/2 - y, z - 1/2 |
C8···C12 | 3.475 (5) | 0.075 | -x, 1 - y, -z |
EHOMO | -6.7318 eV |
ELUMO | -2.4441 eV |
EHOMO-1 | -7.2556 eV |
ELUMO+1 | -1.6506 eV |
EHOMO–ELUMO gap | 4.2877 eV |
EHOMO-1 ELUMO+1 gap | 5.6050 eV |
Chemical hardness (η) | 2.1438 eV |
Chemical potential (µ) | 4.5879 eV |
Electronegativity (χ) | -4.5879 eV |
Electrophilicity index (ω) | 4.9092 eV |
Funding information
KB and PS thank the Department of Science and Technology (DST–SERB), grant No. SB/FT/CS-058/2013, New Delhi, India, for financial support.
References
Altomare, A., Cascarano, G., Giacovazzo, C. & Guagliardi, A. (1993). J. Appl. Cryst. 26, 343–350. CrossRef Web of Science IUCr Journals Google Scholar
Amimoto, K. & Kawato, T. (2005). J. Photochem. Photobiol. Photochem. Rev. 6, 207–226. Web of Science CrossRef CAS Google Scholar
Arunagiri, C., Anitha, A. G., Subashini, A. & Selvakumar, S. (2018). J. Mol. Struct. 1163, 368–378. CrossRef CAS Google Scholar
Bruker (2004). SAINT, APEX2, XPREP and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Diao, Y.-P., Zhang, Q.-H., Wang, D.-C. & Deng, X.-M. (2008). Acta Cryst. E64, o2070. 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
Horkaew, J., Chantrapromma, S., Anantapong, T., Kanjana-Opas, A. & Fun, H.-K. (2012). Acta Cryst. E68, o1069–o1070. CrossRef IUCr Journals Google Scholar
McKinnon, J. J., Jayatilaka, D. & Spackman, M. A. (2007). Chem. Commun. 3814–3816. Google Scholar
Mohanraj, M., Ayyannan, G., Raja, G. & Jayabalakrishnan, C. (2016). Mater. Sci. Eng. C, 69, 1297–1306. CrossRef CAS Google Scholar
Muralisankar, M., Haribabu, J., Bhuvanesh, N. S. P., Karvembu, R. & Sreekanth, A. (2016). Inorg. Chim. Acta, 449, 82–95. Web of Science CrossRef CAS Google Scholar
Rohl, A. L., Moret, M., Kaminsky, W., Claborn, K., McKinnon, J. J. & Kahr, B. (2008). Cryst. Growth Des. 8, 4517–4525. Web of Science CrossRef CAS Google Scholar
Schiff, H. (1864). Justus Liebigs Ann. Chem. 131, 118–119. CrossRef Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Shu, X.-H., Diao, Y.-P., Li, M.-L., Yan, X. & Liu, J. (2009). Acta Cryst. E65, o1034. CrossRef IUCr Journals Google Scholar
Singh, P., Goel, R. L. & Singh, B. P. (1975). J. Indian Chem. Soc. 52, 958–959. CAS Google Scholar
Sivajeyanthi, P., Jeevaraj, M., Balasubramani, K., Viswanathan, V. & Velmurugan, D. (2017). Chem. Data Collect. 11–12, 220-231. CrossRef Google Scholar
Souza, P., Garcia-Vazquez, J. A. & Masaguer, J. R. (1985). Transition Met. Chem. 10, 410–412. CrossRef CAS Web of Science Google Scholar
Spackman, M. A. & Jayatilaka, D. (2009). CrystEngComm, 11, 19–32. Web of Science CrossRef CAS Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Tanaka, K., Shimoura, R. & Caira, M. R. (2010). Tetrahedron Lett. 51, 449–452. Web of Science CrossRef CAS Google Scholar
Tiwari, A. D., Mishra, A. K., Mishra, B. B., Mamba, B. B., Maji, B. & Bhattacharya, S. (2011). Spectrochim. Acta A, 79, 1050–1056. CrossRef CAS Google Scholar
Wang, J., Qu, D., Lei, J.-X. & You, Z. (2017). J. Coord. Chem. 70, 544–555. CrossRef CAS Google Scholar
Wolff, S. K., Grimwood, D. J., McKinnon, J. J., Turner, M. J., Jayatilaka, D. & Spackman, M. A. (2012). Crystal Explorer. University of Western Australia, Australia. Google Scholar
Zhang, M.-J., Yin, L.-Z., Wang, D.-C., Deng, X.-M. & Liu, J.-B. (2009). Acta Cryst. E65, o508. Web of Science CrossRef IUCr Journals Google Scholar
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