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

Vladimir Stilinović, Dominik Cinčić and Branko Kaitner*

Department of Chemistry, Laboratory of General and Inorganic Chemistry, Faculty of Science, Horvatovac 102a, University of Zagreb, 10000 Zagreb, Croatia
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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.

Keywords: Schiff base, terephthaldialdehyde, C–H···N interaction, X-ray structure analysis, thermal analysis