Crystal structure, Hirshfeld surface analysis and HOMO-LUMO analysis of (E)-4-bromo-N'-(4-meth-oxy-benzyl-idene)benzohydrazide.

The title Schiff base compound, C15H13BrN2O2, displays an E configuration with respect to the C=N double bond, which forms a dihedral angle of 58.06 (9)° with the benzene ring. In the crystal, the mol-ecules are linked into chains parallel to the b axis by N-H⋯O and C-H⋯O hydrogen bonds, giving rise to rings with an R 2 1(6) graph-set motif. The chains are further linked into a three-dimensional network by C-H⋯π inter-actions. A Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from C⋯H (33.2%), H⋯H (27.7%), Br⋯H/H⋯Br (14.2%) and O⋯H/H⋯O (13.6%) inter-actions. The title compound has also been characterized by frontier mol-ecular orbital analysis.

Chemical context

n class="Chemical">Schiff basesn> are nitro­gen-containing compounds that were first obtained by the condensation reactions of aromatic amines and aldehydes (Schiff et al., 1864 ▸). A wide range of these compounds with the general formula RHC=NR 1 (R and R 1 can be alkyl, aryl, cyclo­alkyl or heterocyclic groups) have been synthesized. Schiff bases are of great importance in the field of coordination chemistry because they are able to form stable complexes with metal ions (Souza et al., 1985 ▸). The chemical and biological significance of Schiff bases can be attributed to the presence of a lone electron pair in the sp 2-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 and medicine, pharmacy, as well as other new technologies (Tanaka et al., 2010 ▸). Schiff bases 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 ▸). Schiff bases showing photochromic and thermochromic properties have been used in information storage, electronic display systems, optical switching devices and ophthalmic glasses (Amimoto et al., 2005 ▸). Herein the crystal structure of the title compound, (E)-4-bromo-N′-(4-meth­oxy­benzyl­idene)benzohydrazide is reported.

Structural commentary

The asymmetric unit of the title compound (Fig. 1 ▸) consists of one independent mol­ecule displaying an E configuration about the C=N double bond. All the bond l<span class="Gene">engths are within the normal ranges. The values of the C8=N2 [1.281 (3) Å] and C7=O2 [1.222 (3) Å] bond l<span class="Gene">engths confirm their double-bond character. The C7—N1, N1—N2 and C3—Br1 bond lengths are 1.354 (3), 1.379 (3) and 1.894 (3) Å, respectively. The central O2/C7/N1/N2 fragment is approximately planar (r.m.s. deviation 0.0141 Å) and forms dihedral angles of 32.5 (2) and 27.2 (2)° with the C1–C6 and C9–C14 rings, respectively. The dihedral angle formed by the aromatic rings is 58.06 (9)°.

Figure 1

The mol­ecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level.

Supra­molecular features

In the crystal structure, the mol­ecules are linked into chains extending along the b-axis direction by N1—H1N⋯O2 and C8—H8⋯O2 <span class="Chemical">hydrogen-bonding inter­actions (Table 1 ▸) forming rings with an (6) graph-set motif (Fig. 2 ▸). The chains are further connected by C—H⋯π inter­actions, forming a three-dimensional network (Fig. 3 ▸).

Table 1

Hydrogen-bond geometry (Å, °)

Cg1 and Cg2 are the centroids of the C1–C6 and C9–C14 rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1N⋯O2i	0.86	2.40	3.193 (3)	154
C8—H8⋯O2i	0.93	2.43	3.240 (3)	146
C2—H2⋯Cg2ii	0.93	2.81	3.531 (4)	135
C5—H5⋯Cg1iii	0.93	2.89	3.553 (4)	130
C10—H10⋯Cg1iv	0.93	2.86	3.549 (4)	132

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) .

Figure 2

Partial packing diagram of the title compound showing the formation of a mol­ecular chain parallel to the b axis through N—H⋯O and C—H⋯O hydrogen bonds (dashed lines).

Figure 3

Packing diagram of the title compound viewed down the b axis.

Hirshfeld surface analysis

The three-dimensional d norm surface is a useful tool for analysing and visualizing the inter­molecular inter­actions. d norm takes negative or positive values depending on whether the inter­molecular contact is shorter or longer, respectively, than the van der Waals radii (<span class="Chemical">Spackman & Jayatilaka, 2009 ▸; McKinnon et al., 2007 ▸). The three-dimensional d norm surface of the title compound is shown in Fig. 4 ▸. The red points, which represent closer contacts and negative d norm values on the surface, correspond to the N—H⋯O and C—H⋯O inter­actions. Two-dimensional fingerprint plots from Hirshfeld surface analysis (Fig. 5 ▸) provide information about the inter­molecular contacts and their percentage contributions to the Hirshfeld surface. The percentage contributions from the different inter­atomic contacts to the Hirshfeld surface in the title compound are as follows: C⋯H (33.2%), H⋯H (27.7%), Br⋯H/H⋯Br (14.2%), O⋯H/H⋯O (13.6%), N⋯H/H⋯N (4.6%), Br⋯O/O⋯Br (2.4%), C⋯N/N⋯C (1.6%), O⋯N/N⋯O (1.3%), O⋯C/C⋯O (0.6%), Br⋯N/N⋯Br (0.5%) and Br⋯C/C⋯Br (0.3%).

Figure 4

Hirshfeld surfaces of the title compound mapped over d norm.

Figure 5

Two-dimensional fingerprint plots of the title compound and relative contributions of the atom pairs to the Hirshfeld surface.

Frontier mol­ecular orbitals

The HOMO (highest occupied mol­ecular orbital) acts as an electron <span class="Species">donorn> and the LUMO (lowest occupied mol­ecular orbital) acts as an electron acceptor. If the energy gap is small then the mol­ecule is highly polarizable and has high chemical reactivity. The energy levels were computed by the DFT-B3LYP/6-311G++(d,p) method (Becke, 1993 ▸) as implemented in GAUSSIAN09 (Frisch et al., 2009 ▸). The electron distribution of the HOMO-1, HOMO, LUMO and LUMO+1 energy levels, which determines the chemical stability, chemical <span class="Disease">hardness, chemical potential, electronegativity and electrophilicity index (Table 2 ▸), are shown in Fig. 6 ▸. 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 <span class="Species">donor and acceptor groups. From the HOMO–LUMO energy gap, information on whether or not the mol­ecule is difficult (hard) or delicate (soft) can be derived. If the mol­ecule has a large energy gap, then the mol­ecule can be defined as a hard mol­ecule whereas the presence of a small energy gap classifies the mol­ecule as soft. The soft mol­ecules are more polarizable than the hard ones because they only need a small energy for excitation. Therefore, from the data reported in Table 2 ▸, we conclude that the mol­ecule of the title compound belongs to the really hard materials.

Table 2

Calculated frontier mol­ecular orbital energies (eV)

FMO	Energy
E HOMO	−6.0275
E LUMO	−1.9434
E HOMO−1	−7.0785
E LUMO+1	−1.2582
(E HOMO − E LUMO) gap	4.0841
(E HOMO−1 − E LUMO+1) gap	5.8203
Chemical hardness	2.0420
Chemical potential	3.9854
Electronegativity	−3.9854
Electrophilicity index	3.8892

Figure 6

Mol­ecular orbital energy levels of the title compound.

Database survey

A search of the Cambridge Structural Database (Version 5.39, update May 2018; Groom et al., 2016 ▸) for uncoordinated mol­ecules containing the 4-bromo­benzohydrazide fragment yielded 17 hits. Similar to the crystal structure of the title compound, in seven of them the carbonyl oxygen atom is <span class="Gene">engaged in inter­molecular N—H⋯O and C—H⋯O <span class="Chemical">hydrogen bonds as a bifurcated acceptor [4-bromo-N′-(2,4-di­hydroxy­benzyl­idene)benzohydrazide (Mohanraj et al., 2016 ▸; Arunagiri et al., 2018 ▸); 4-bromo-N′-(2-nitro­benzyl­idene)benzohydrazide (Zhang et al. 2009 ▸); 4-bromo-N′-(2-hy­droxy-5-meth­oxy­benzyl­idene)benzohydrazide (Wang et al., 2017 ▸)] or trifurcated acceptor [4-bromo-N′-(2-chloro­benzyl­idene)benzohydrazide (Shu et al., 2009 ▸); 4-bromo-N′((5-methyl­furan-2-yl)methyl­ene)benzohydrazide (Bai & Jing, 2007 ▸); 4-bromo-N′-(4-methyl-1,2,3-thia­dizole-5-yl)methyl­idenebenzohydrazine (Zhang et al., 2017 ▸); (2-fluoro-2-methyl-2-phenyl­ethyl­idene) 4-bromo­benzoyl hydrazone (Brandes et al., 2006 ▸)], forming mol­ecular chains.

Synthesis and crystallization

The title compound was synthesized by the reaction of a 1:1 molar ratio mixture of a hot ethano­lic solution (20 mL) of 4-bromo­benzohydrazide (0.213 mg) and a hot ethano­lic solution of 4-meth­oxy­benzaldehyde (0.136 mg). The mixture was refluxed for 8 h, then it was cooled and kept at room temperature. The powder formed was recrystallized from <span class="Chemical">DMSO. Colourless block-shaped crystals suitable for X-ray analysis were obtained after a few days on slow evaporation of the solvent.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3 ▸. The <span class="Chemical">hydrogen atoms were positioned geometrically (C—H = 0.93–0.9 Å, N—H = 0.86 Å) and were refined as riding with U iso(H) = 1.2U eq(C, N) or 1.5U eq(C) for methyl <span class="Disease">H atoms. A rotating model was used for the methyl <span class="Disease">H atoms. Three outliers (100, 02, 002) were omitted in the last cycles of refinement.

Table 3

Experimental details

Crystal data
Chemical formula	C15H13BrN2O2
M r	333.18
Crystal system, space group	Monoclinic, P21/c
Temperature (K)	296
a, b, c (Å)	15.6963 (14), 5.4121 (4), 18.6224 (16)
β (°)	119.609 (6)
V (Å3)	1375.4 (2)
Z	4
Radiation type	Mo Kα
μ (mm−1)	2.99
Crystal size (mm)	0.30 × 0.20 × 0.20
Data collection
Diffractometer	Bruker Kappa APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2004 ▸)
T min, T max	0.467, 0.586
No. of measured, independent and observed [I > 2σ(I)] reflections	9456, 2563, 1923
R int	0.030
(sin θ/λ)max (Å−1)	0.606
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.032, 0.073, 1.02
No. of reflections	2563
No. of parameters	182
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	0.46, −0.49

Computer programs: APEX2, SAINT and XPREP (Bruker, 2004 ▸), SIR92 (Altomare et al., 1999 ▸), SHELXL2017/1 (Sheldrick, 2015 ▸), ORTEP-3 for Windows (Farrugia, 2012 ▸) and Mercury (Macrae et al., 2008 ▸).

Crystal structure: contains datablock(s) global, I, 1. DOI: 10.1107/S2056989018013373/rz5241sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989018013373/rz5241Isup2.hkl

Click here for additional data file.

Supporting information file. DOI: 10.1107/S2056989018013373/rz5241Isup3.cml

CCDC reference: 1587248

Additional supporting information: crystallographic information; 3D view; checkCIF report

C15H13BrN2O2	F(000) = 672
Mr = 333.18	Dx = 1.609 Mg m−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 15.6963 (14) Å	Cell parameters from 3040 reflections
b = 5.4121 (4) Å	θ = 6.0–48.0°
c = 18.6224 (16) Å	µ = 2.99 mm−1
β = 119.609 (6)°	T = 296 K
V = 1375.4 (2) Å3	Block, colourless
Z = 4	0.30 × 0.20 × 0.20 mm

Bruker Kappa APEX2 CCD diffractometer	1923 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.030
ω and φ scan	θmax = 25.5°, θmin = 2.8°
Absorption correction: multi-scan (SADABS; Bruker, 2004)	h = −19→18
Tmin = 0.467, Tmax = 0.586	k = −6→6
9456 measured reflections	l = −20→22
2563 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)] = 0.032	Hydrogen site location: mixed
wR(F2) = 0.073	H-atom parameters constrained
S = 1.02	w = 1/[σ2(Fo2) + (0.0247P)2 + 1.0475P] where P = (Fo2 + 2Fc2)/3
2563 reflections	(Δ/σ)max = 0.002
182 parameters	Δρmax = 0.46 e Å−3
0 restraints	Δρmin = −0.49 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.

	x	y	z	Uiso*/Ueq
Br1	0.79167 (2)	0.30890 (7)	0.92827 (2)	0.05897 (14)
O1	−0.00864 (14)	0.0494 (4)	0.09196 (11)	0.0533 (5)
O2	0.43709 (15)	0.7268 (4)	0.55090 (12)	0.0549 (5)
N1	0.41072 (16)	0.3124 (4)	0.53160 (13)	0.0409 (5)
H1N	0.427566	0.168774	0.554028	0.049*
N2	0.33475 (16)	0.3322 (4)	0.45146 (13)	0.0407 (6)
C1	0.59886 (19)	0.2470 (5)	0.67875 (17)	0.0372 (6)
H1	0.586962	0.133251	0.637387	0.045*
C2	0.67360 (19)	0.2047 (5)	0.75843 (16)	0.0381 (6)
H2	0.712459	0.064141	0.770697	0.046*
C3	0.68987 (18)	0.3718 (5)	0.81921 (15)	0.0355 (6)
C4	0.63465 (19)	0.5837 (5)	0.80198 (16)	0.0382 (6)
H4	0.646969	0.696761	0.843605	0.046*
C5	0.56079 (19)	0.6261 (5)	0.72216 (16)	0.0365 (6)
H5	0.523578	0.769580	0.710036	0.044*
C6	0.54134 (18)	0.4582 (5)	0.65996 (15)	0.0322 (6)
C7	0.45937 (19)	0.5147 (5)	0.57559 (16)	0.0379 (7)
C8	0.28735 (19)	0.1307 (5)	0.42189 (16)	0.0390 (7)
H8	0.304278	−0.008120	0.455644	0.047*
C9	0.20794 (19)	0.1129 (5)	0.33719 (16)	0.0342 (6)
C10	0.19274 (19)	0.2921 (5)	0.27816 (16)	0.0379 (6)
H10	0.232143	0.432276	0.293687	0.046*
C11	0.1207 (2)	0.2643 (5)	0.19783 (16)	0.0410 (7)
H11	0.112410	0.384465	0.159190	0.049*
C12	0.05982 (19)	0.0593 (5)	0.17324 (16)	0.0379 (6)
C13	0.0727 (2)	−0.1177 (5)	0.23154 (17)	0.0411 (7)
H13	0.031518	−0.254468	0.216485	0.049*
C14	0.1471 (2)	−0.0895 (5)	0.31222 (16)	0.0407 (7)
H14	0.156194	−0.210907	0.350718	0.049*
C15	−0.0603 (2)	−0.1750 (6)	0.06035 (19)	0.0606 (9)
H15A	−0.014576	−0.309608	0.077155	0.091*
H15B	−0.096720	−0.167091	0.001142	0.091*
H15C	−0.104507	−0.200227	0.081334	0.091*

	U11	U22	U33	U12	U13	U23
Br1	0.0530 (2)	0.0698 (2)	0.03805 (19)	0.00375 (18)	0.01023 (14)	0.00735 (16)
O1	0.0519 (12)	0.0497 (13)	0.0362 (11)	−0.0031 (11)	0.0050 (10)	0.0048 (10)
O2	0.0543 (13)	0.0428 (13)	0.0510 (13)	0.0078 (10)	0.0132 (10)	0.0112 (10)
N1	0.0423 (13)	0.0417 (14)	0.0299 (12)	0.0040 (12)	0.0113 (10)	0.0069 (11)
N2	0.0389 (13)	0.0491 (16)	0.0274 (12)	0.0054 (12)	0.0112 (10)	0.0062 (11)
C1	0.0391 (15)	0.0326 (15)	0.0418 (16)	−0.0027 (12)	0.0213 (13)	−0.0107 (12)
C2	0.0346 (14)	0.0325 (15)	0.0426 (16)	0.0040 (13)	0.0156 (13)	0.0017 (13)
C3	0.0316 (14)	0.0403 (16)	0.0324 (15)	−0.0032 (12)	0.0142 (12)	0.0038 (12)
C4	0.0415 (16)	0.0362 (15)	0.0395 (16)	−0.0032 (14)	0.0218 (13)	−0.0060 (13)
C5	0.0377 (15)	0.0280 (14)	0.0460 (16)	0.0063 (12)	0.0224 (13)	0.0035 (12)
C6	0.0319 (14)	0.0319 (14)	0.0356 (15)	0.0010 (12)	0.0187 (12)	0.0034 (12)
C7	0.0363 (15)	0.0397 (18)	0.0395 (16)	0.0043 (14)	0.0202 (13)	0.0045 (13)
C8	0.0400 (16)	0.0409 (17)	0.0359 (15)	0.0065 (14)	0.0185 (13)	0.0065 (13)
C9	0.0361 (15)	0.0344 (15)	0.0336 (14)	0.0059 (12)	0.0184 (12)	0.0019 (12)
C10	0.0394 (15)	0.0317 (14)	0.0429 (16)	−0.0008 (13)	0.0205 (13)	0.0015 (13)
C11	0.0464 (17)	0.0343 (16)	0.0382 (16)	0.0039 (13)	0.0179 (14)	0.0099 (12)
C12	0.0361 (15)	0.0385 (16)	0.0384 (16)	0.0043 (14)	0.0178 (13)	0.0022 (13)
C13	0.0435 (17)	0.0345 (15)	0.0442 (17)	−0.0034 (13)	0.0208 (14)	0.0013 (13)
C14	0.0520 (18)	0.0333 (15)	0.0377 (16)	0.0033 (14)	0.0229 (14)	0.0084 (13)
C15	0.0538 (19)	0.055 (2)	0.0473 (19)	−0.0075 (17)	0.0054 (16)	−0.0005 (16)

Br1—C3	1.894 (3)	C5—H5	0.9300
O1—C12	1.357 (3)	C6—C7	1.490 (4)
O1—C15	1.416 (3)	C8—C9	1.452 (4)
O2—C7	1.222 (3)	C8—H8	0.9300
N1—C7	1.354 (3)	C9—C14	1.375 (4)
N1—N2	1.379 (3)	C9—C10	1.395 (4)
N1—H1N	0.8600	C10—C11	1.367 (4)
N2—C8	1.281 (3)	C10—H10	0.9300
C1—C2	1.382 (4)	C11—C12	1.386 (4)
C1—C6	1.390 (3)	C11—H11	0.9300
C1—H1	0.9300	C12—C13	1.386 (4)
C2—C3	1.371 (4)	C13—C14	1.382 (4)
C2—H2	0.9300	C13—H13	0.9300
C3—C4	1.376 (4)	C14—H14	0.9300
C4—C5	1.380 (4)	C15—H15A	0.9600
C4—H4	0.9300	C15—H15B	0.9600
C5—C6	1.382 (4)	C15—H15C	0.9600
C12—O1—C15	118.2 (2)	N2—C8—H8	119.1
C7—N1—N2	121.3 (2)	C9—C8—H8	119.1
C7—N1—H1N	119.4	C14—C9—C10	117.9 (2)
N2—N1—H1N	119.3	C14—C9—C8	120.0 (2)
C8—N2—N1	114.0 (2)	C10—C9—C8	122.0 (2)
C2—C1—C6	120.5 (2)	C11—C10—C9	120.9 (3)
C2—C1—H1	119.7	C11—C10—H10	119.6
C6—C1—H1	119.7	C9—C10—H10	119.6
C3—C2—C1	119.3 (2)	C10—C11—C12	120.8 (2)
C3—C2—H2	120.3	C10—C11—H11	119.6
C1—C2—H2	120.3	C12—C11—H11	119.6
C2—C3—C4	121.2 (2)	O1—C12—C13	125.1 (3)
C2—C3—Br1	118.7 (2)	O1—C12—C11	115.9 (2)
C4—C3—Br1	120.0 (2)	C13—C12—C11	119.0 (2)
C3—C4—C5	119.1 (2)	C14—C13—C12	119.5 (3)
C3—C4—H4	120.4	C14—C13—H13	120.2
C5—C4—H4	120.4	C12—C13—H13	120.2
C4—C5—C6	120.9 (2)	C9—C14—C13	121.9 (2)
C4—C5—H5	119.6	C9—C14—H14	119.1
C6—C5—H5	119.6	C13—C14—H14	119.1
C5—C6—C1	118.9 (2)	O1—C15—H15A	109.5
C5—C6—C7	117.8 (2)	O1—C15—H15B	109.5
C1—C6—C7	123.3 (2)	H15A—C15—H15B	109.5
O2—C7—N1	124.1 (3)	O1—C15—H15C	109.5
O2—C7—C6	121.8 (3)	H15A—C15—H15C	109.5
N1—C7—C6	114.0 (2)	H15B—C15—H15C	109.5
N2—C8—C9	121.9 (2)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···O2i	0.86	2.40	3.193 (3)	154
C8—H8···O2i	0.93	2.43	3.240 (3)	146
C2—H2···Cg2ii	0.93	2.81	3.531 (4)	135
C5—H5···Cg1iii	0.93	2.89	3.553 (4)	130
C10—H10···Cg1iv	0.93	2.86	3.549 (4)	132