Crystal structure of two N′-(1-phenylbenzylidene)-2-(thiophen-3-yl)acetohydrazides

Two N′-(1-(phenylethylidene)-2-(thiophen-3-yl)acetohydrazides containing –OH and –OCH3 at the para-position of the phenyl ring have been synthesized and their molecular and crystal structures are reported.


Chemical context
Acetohydrazides are considered to be good candidates for different pharmaceutical applications, including their use as antibacterial, antifugal, antimicrobial and anticonvulsant agents (Yadav et al., 2015;Bharti et al., 2010;Loncle et al., 2004;Papakonstantinou-Garoufalias et al., 2002). Moreover, many of them have shown analgesic and antiplatelet properties (Wardakhan et al., 2013). Combinations of acetohydrazide with other heterocyclic rings have also been investigated, such as the hydrazide-based 2-oxonicotinonitrile derivatives that are considered to be potential antimicrobial agents (El-Sayed et al., 2018).
As a continuation of our research Vu et al., , 2017 on the chemical and physical properties of novel polythiophenes, a new thiophene monomer-containing acetohydrazide has been prepared. We have synthesized two N 0 -(1-(phenylbenzylidene)-2-(thiophen-3-yl)acetohydrazides and present here the spectroscopic data and crystal structures ISSN 2056-9890 of the title compounds, together with the Hirshfeld surface analysis.

Supramolecular features
In the crystal, molecules of (3a) are connected by N9-H9Á Á ÁO8 i [symmetry code: (i) Àx + 1 2 , y + 1 2 , z] hydrogen bonds, resulting in the formation of chains in the b-axis direction with a C 1 1 (4) graph-set motif (Fig. 3 The molecular structure of (3b) with atom labels and 50% probability displacement ellipsoids.

Figure 1
A view of the molecular structure of (3a), with atom labels and displacement ellipsoids drawn at the 50% probability level. The minordisorder component is shown in light green.

Figure 4
Part of the crystal structure of (3a), illustrating the chain formation through O-HÁ Á ÁO interactions (red dashed lines) along the a-axis direction. The minor disorder component is not shown. Symmetry codes: (i) x + 1 2 , y, Àz + 1 2 ; (ii) x À 1 2 , y, Àz + 1 137 hits. Histograms of the distribution of the four torsion angles 1 -4 along the linker backbone are shown in Fig. 7b-e [the red and green lines depict the torsion angles for title compounds (3a) and (3b), respectively]. The histogram of 1 reflects a wide spread with a preference for the Àap/+ap conformation, followed by the Àsc/+sc conformation and only a few entries in the remaining regions. In the case of torsion angle 2 , two regions are preferred: Àap/+ap [for the majority of the entries and similar to (3a)] and Àsp/+sp [similar to (3b)]. Torsion angles 3 and 4 show both a narrow spread in the region Àap/+ap.

Synthesis and crystallization
The reaction scheme to synthesize the title compounds, (3a) and (3b), is given in Fig. 9.

Refinement details
Crystal data, data collection and structure refinement details are summarized in Table 3. All H atoms were placed in idealized positions and refined in riding mode, with U iso (H) values assigned as 1.2U eq of the parent atoms (1.5 times for methyl groups), with C-H distances of 0.93 (aromatic), 0.96 (CH 3 ) and 0.97 Å (CH 2 ), N-H distances of 0.86 Å and O-H distances of 0.82 Å (rotating OH). In (3a), the thiophene ring is disordered over two positions [population parameters 0.762 (3) and 0.238 (3)] and was refined with restraints for the bond lengths and angles in the ring. The anisotropic temperature factors for atoms S1, C2, C4 and C5 in both orientations were constrained to be equal. In the final cycles of refinement, four and two outliers were omitted for (3a) and (3b), respectively.