Lanthanide Complexes with N,N-Bis-(2-hydroxy-5-nitrobenzylidene)-1,2-phenylenediamine Schiff Base Ligand: Synthesis, Characterization, Photophysical Properties, and Biological Activity

摘要

A series of lanthanides(III) complexes containing Schiff base ligand, {[LnL(NO3).H2O]center dot xH(2)O {Ln: La, Pr, Nd, Sm, Eu, Gd, Tb, and Dy, H2L: N,N-bis-(2-hydroxy-5-nitro-benzylidene)-1,2-phenylenediamine Schiff base ligand}, have been synthesized by reaction of the ligand with Ln(NO3)(3)center dot xH(2)O in the presence of NaOH. Structures of these complexes have been characterized by elemental analysis, molar conductivity, thermal gravimetric and various spectral methods (IR, UV-Vis, H-1, and C-13 NMR). The proposed formula, of the complexes consists of one Ln(III) ion with the coordination number of seven. Two coordination sites are occupied by one bi-dentate nitrate anion, another site is occupied by one water molecule and the remaining four coordination sites are occupied by one deprotonated tetra-dentate ligand molecule. Fluorescence emission spectra of Ln(III) complexes exhibit ligand-centred emission peak with a blue shift compared with that of free H2L. This can be explained on the basis of ligand-to-metal charge transfer (LMCT) that occurs upon L-2 coordination to Ln(III) ions. Antibacterial activity of H2L and its Ln(III) complexes has been tested against some gram-positive and gram-negative bacterial strains.