Synthesis and Characterization of New Tetradentate Ligands

Four new tetradentate ligands [1–4] have been prepared by a 1:2 molar condensation of an aromatic dialdehyde (terephthalaldehyde) with thiophen-2-ylmethanamine, 2-(thiophen-2-yl)ethanamine, pyridin-2-ylmethanamine and 2-(pyridin-2-yl)ethanamine. The ligands were characterised on the basis of their elemental analysis, IR spectroscopies, 1H, 13C NMR, ESI-mass spectrometry and for ligands 1, 2 and 4 also by X-ray diffraction. The crystal structures reveal that the ligands exist as discrete molecules with an average C–N bond distance of 1.2656 Å which is consistent with C=N double bonding.