Crystal structures of the Schiff base derivatives (E)-N′-[(1H-indol-3-yl)methylidene]isonicotinohydrazide ethanol monosolvate and (E)-N-methyl-2-[1-(2-oxo-2H-chromen-3-yl)ethylidene]hydrazinecarbothioamide

In the two title Schiff base derivatives, the (E)-N′-[(1H-indol-3-yl)methylidene]isonicotinohydrazide molecules and (E)-N-methyl-2-[1-(2-oxo-2H-chromen-3-yl)ethylidene]hydrazinecarbothioamide molecules form a tape structure and a helical chain structure, respectively, through hydrogen bonds.


Chemical context
Schiff base derivatives are a biologically versatile class of compounds possessing diverse activities, such as anti-oxidant (Haribabu, Subhashree et al., 2015, anti-inflammatory (Alam et al., 2012), anti-cancer (Creaven et al., 2010;Haribabu, Jeyalakshmi et al., 2015, anti-bacterial (Sondhi et al., 2006), anti-fungal (Jarrahpour et al., 2007), anti-convulsant (Bhat & Al-Omar, 2011). Schiff bases have gained special attention in pharmacophore research and in the development of several bioactive lead molecules. They are widely used as catalysts, corrosion inhibitors and intermediates in organic synthesis, and also play a potential role in the development of coordination chemistry (Muralisankar et al., 2016). As part of our studies in this area, we have synthesized the title Schiff base compounds, 1ÁEtOH and 2, and determined their crystal structures.

Database survey
A search of the Cambridge Structural Database (Groom et al., 2016)  The molecular structure of compound 1ÁEtOH, with the atom labelling. Displacement ellipsoids of non-H atoms are drawn at 30% probability level.

Synthesis and crystallization
Compound 1 was synthesized by condensing equimolar amounts of 1H-indole-3-carbaldehyde (145 mg, 1 mmol) with nicotinic acid hydrazide (137 mg, 1 mmol) in ethanol. The reaction mixture was then refluxed on a water bath for 5 h and poured into crushed ice. The corresponding solid Schiff base that formed was filtered, washed several times with distilled water and dried under vacuum. The compound was recrystallized from an ethanol-chloroform (1:3) solvent mixture, yielding the ethanol solvate compound, 1ÁEtOH. Similarly, compound 2 was synthesized from equimolar amounts of 3acetyl-2H-chromen-2-one (188 mg, 1 mmol) with N-methylhydrazinecarbothioamide (105 mg, 1 mmol) in ethanol.

Special details
Experimental. SADABS-2014/3 (Bruker, 2014 was used for absorption correction. wR2(int) was 0.1205 before and 0.0824 after correction. The Ratio of minimum to maximum transmission is 0.9082. The λ/2 correction factor is not present. 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.   (

Special details
Experimental. For component 1: wR2(int) was 0.1337 before and 0.0605 after correction. The ratio of minimum to maximum transmission is 0.72. The λ/2 correction factor is not present Final HKLF 4 output contains 20988 reflections, Rint = 0.0871 (9738 with I > 3sig(I), Rint = 0.0747) 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. The absorption correction program TWINABS2 was employed to correct the data for absorption effects, as well as to separate hkl files for the domains with major component, which was used for further analysis. Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 ) x y z U iso */U eq S1 0.80937 (6) 1.04558 (5)  0.0320 (9) 0.0280 (9) 0.0343 (9) −0.0001 (7) 0.0055 (7) −0.0140 (7)