Positional isomers of (E)-2-(anthracen-9-ylmethylene)-N-(aryl)hydrazinecarbothioamide, zinc complexes and polymorphic solvates†

Abstract

The synthesis, energy calculation and analysis of the weak interactions of two sets of positional isomers of (E)-2-(anthracen-9-ylmethylene)-N-(aryl)hydrazinecarbothioamide, one set with aryl = 3-OCH₃- or 4-OCH₃-phenyl and the other with aryl = 2,3 or 3,4-dichlorophenyl, were carried out. The nature of substituent/s and their positions in the rings rendered large differences in the angle between the anthracenyl and aryl planes at the distal ends. The respective bis-chelated zinc complexes of these positional isomers had a see-saw geometry. There was one dimethylformamide (DMF) molecule of crystallisation in the zinc complex of the bis-chelated 3-methoxyphenyl containing ligand, but a similar zinc complex with a 4-methoxyphenyl containing ligand had three DMF molecules per complex, due to the packing differences contributed through interplay of weak interactions. The zinc complex of the 2,3-dichloroaryl derived ligand had chloroform as a solvent crystallisation molecule and it showed two polymorphs of the chloroform solvated complex. One of the solvate polymorphs had intermolecular association with chloroform, it lost crystallinity very easily. Meanwhile, the other polymorphic solvate had intra-molecular hydrogen bonded chloroform molecules, crystals of this polymorph were stable enough to be characterized by several spectroscopic tools. The stable polymorph had S⋯π interactions forming a dimeric assembly. A similar zinc complex of the 3,4-dichloro-aryl group derived ligand had extensive stacking among the anthracenyl units in the lattice. It accommodated chloroform molecules of crystallization embedded in the lattice.