Synthesis, characterizations and photo-physical properties of novel lanthanum(III) complexes

Abstract

A series of novel complexes of La(III) with substituted pyrazolines and mixed ligand complexes with these pyrazolines and thio-ligands have been synthesized and characterized by elemental analysis, molecular weight measurement, Fourier transform infra-red, 1H and 13C NMR spectroscopy. The particle/crystallite sizes were confirmed by powder X-ray diffraction, scanning electron microscopy and transmission electron microscopic techniques. Optical characterizations have been performed by electronic absorption and fluorescence emission spectroscopies in order to investigate their luminescence behaviour, which reveals fairly good quantum yield and fluorescence life time for some of the complexes. Thermal analyses such as thermogravimetric and differential thermal analysis indicate that these complexes are thermally stable at high temperature. Investigations pertaining to solid-state optical absorption spectra and photoelectron yield spectroscopy reveal that upon thermal annealing beyond 300°C, these compounds form dark-brown to black semiconducting materials with an optical band gap between 1.9 and 2.3 eV. Abbreviations: La-PyH : La-HPY = [La(C15H12N2OH)2(H2O)Cl]; La-PyH-dtc = [La(C15H12N2OH)(C5H10NS2)(2H2O)Cl]; La-OCPy-xan: [La(C15H12N2OOCH3)(C2H5OCS2)(2H2O)Cl].