Spectroscopic differences between heterocyclic benzothiazoline, -thiazole and imine containing ligands and comparison of the Co and Cu pyridine benzothiazole and imine complexes

Five heterocyclic benzothiazoline and -thiazole analogs have been synthesized and characterized by H-1 NMR and IR spectroscopy. The analogs fall into two different classes, (a) those which contain one benzothiazoline group adjacent to the heterocyclic ring system (starting with 2-pyridinecarboxaldehyde, 2-thiophenecarboxaldehyde or 2-furaldehyde), and (b) those which have two benzothiazoline substituents (starting with 2,6-pyridinecarboxaldehyde and 2,5-thiohenecarboxaldehyde). In addition, the imine containing ligands, bis-2-[(pyridin-2-ylmethylene)-imino]-benzenethiol disulfide (PyIS)(2) and bis-2-[(thiophen-2-ylmethylene)-imino]-benzenethiol disulfide(ThIS)(2), were prepared starting with the disulfide of 2-aminothiophenol. Each species has been characterized by H-1 NMR and IR spectroscopies. Ligation reactions with 2-(2-pyridyl) benzothiazoline (Py(Bt)) and Cu(OAc)(2)center dot 1H(2)O resulted in the formation of a dinuclear species containing two copper ions, two ligand frames and two acetate groups, [Cu(PyA-S)( OAc)](2) (1). Both copper ions are five-coordinate and bonded to one monodentate acetate, one ligand frame (NNS) and one bridging thiolate. Ligation reaction with 2-(2-pyridyl) benzothiazole (Py(oBt)) and CoCl2 center dot xH(2)O or Cu(BF4)(2)center dot xH(2)O resulted in the formation of a six-coordinate, octahedral Co(II) complex, cis-[Co(Py(oBt)(2)Cl-2] (2) and a five coordinate Cu(II) complex, [Cu(Py(oBt))(2)(OH2)](BF4) (3), respectively. All complexes have been characterized by X-ray crystallography as well as UV-Vis and IR spectroscopy. (C) 2010 Elsevier B.V. All rights reserved.