The Effect of C–H•••N Interactions on Crystal Structure and Thermal Properties of Two Novel Diamine Schiff Bases Derived from Terephthaldialdehyde

Two novel potential bridging ligands derived from terephtaldialdehyde, namely 1,4-bis((pyridine-3-ylimino) methyl)benzene (1) and 1,4-bis-((1-benzylpiperidin-4-ylimino)methyl)benzene (2), were prepared by the Schiff base condensation. They were characterised by means of IR spectroscopy, thermal analysis and also by powder and singlecrystal X-ray diffraction. The molecules of 1 form 1D chains by intermolecular C–H•••N interactions. The molecular conformation of 2, governed by intramolecular C–H•••N interactions, does not permit formation of intermolecular interactions analogous to those in 1. As a consequence, 2 has a markedly lower melting point and fusion enthalpy than 1, although its molecular weight is almost double that of 1.