A multi-technique investigation of a new macroacyclic Schiff base ligand and its Cd(II), Zn(II) and Cu(II) complexes

摘要

A new macroacyclic Schiff base, 1,3-bis(2((Z)-(hydroxyethylimino)methyl) phenoxy)propan-2-ol, (H3L), was synthesized and characterized by infrared, ultraviolet-visible and NMR spectroscopies, and microanalysis. A series of new complexes was subsequently obtained from the reaction of the H3L ligand and Cd(II), Zn(II) and Cu(II). The prepared complexes [Cd2H2L(H2O)(NO3)(2)]NO3 (1), [ZnH2L]ClO4 (2), and [CuH2L]ClO4 (3), were characterized by IR spectroscopy and microanalysis, and, in the case of 1 and 2, also by NMR spectroscopy. Suitable crystals of 1 were obtained for X-ray analysis. The single crystal X-ray structural analysis of 1 showed that the complex is binuclear, with all nitrogen and oxygen atoms of the ligand (N2O5) coordinated to the two Cd(II) ions. In the crystal structure the two distorted mono-capped anti-prism Cd(II) centers are bridged asymmetrically by an oxygen of a hydroxyl group of the Schiff base and a water molecule. Density functional theory calculations were performed to characterize the conformational equilibrium of the Schiff base in solution. The geometry and the C-13 NMR spectrum of the Cd(II) complex were also calculated by DFT, confirming the presence of the complex in the investigated solution media. Time dependent-DFT calculations provided further insight on the interpretation of the experimental UV-Vis spectrum of the Cd(II) complex.