Photophysical properties and computational study of newly synthesized lanthanide complexes with N-(2-carboxyphenyl)salicylideneimine Schiff base ligand

Abstract New lanthanide complexes [Ln( LH 2 ) 2 (NO 3 ) 2 ]NO 3 have been synthesized by reaction of Ln(NO 3 ) 3 · x H 2 O {Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Er} with N -(2-carboxyphenyl)salicylideneimine Schiff base ligand ( LH 2 ). A ten-coordinated lanthanide structure has been proposed based on elemental analysis, spectroscopic analysis (UV–Visible, FT-IR, 1 H and 13 C NMR), molar conductance and thermal analysis. The molecular geometry of the cationic complex [Sm(LH 2 )(NO 3 ) 2 ] + has been examined using DFT calculations at the B3LYP/6-31 G(d) level of theory and the obtained results are in good agreement with the experimental data. The absorption, excitation and emission spectral characteristic of LH 2 and Ln-LH 2 complexes in DMF and methanol have been investigated. The Eu-LH 2 , Sm-LH 2 and Tb-LH 2 complexes display characteristic lanthanide-centered luminescence. The antioxidant activity of LH 2 ligand and its Ln(III) complexes has been estimated in terms of the DPPH free radical scavenging activity (DPPH-RSA). The photoconductivity of the LH 2 ligand and Ln-LH 2 (Pr, Gd, Nd, Sm, and Tb) complexes has also been studied. The results show that Pr-LH 2 , Nd-LH 2 and Gd-LH 2 complexes exhibit a remarkable photoconductivity.