Synthesis and comparative study of spectral properties of mixed ligand complexes of lanthanides with 2, 5-dihydroxy butyrophenone thiosemicarbazones and 1, 10-phenanthroline

Synthesis of mixed ligand complexes of Lanthanide (III) metal ion [LnL1L2]Cl was carried out [where Ln = La, Ce, Pr, Nd & Sm and L1 = 2, 5-Dihydroxy butyrophenone thiosemicarbazones as a primary ligand and L2 = 1, 10-phenanthroline as a co-ligand] and discussion of their physicochemical properties. Analytical results correspond to 1: 1: 1 (M-L1-L2) stoichiometry for the isolated complexes. The complexes are stable and have no tendency of absorbing moisture from the atmosphere. These compounds are fairly soluble in chloroform, ethanol, acetone, DMSO and DMF. The molar conductance in ethanolic solution suggests 1: 1 electrolytic behavior of these complexes. The stereochemistry of these complexes has been established on the basis of Electronic and IR spectral studies. The values of β, δ%, b^1/2 and η for the isolated complexes have also been calculated. The value of δ has been found to be positive in all the complexes which suggests the electron delocalization from 4f-orbital. The positive values of b^1/2 show considerable amount of covalency in the metal-ligand bond. The magnitudes of covalency parameter and bonding parameter increases from Pr(III) to Sm(III) indicating that the extent of covalent character of metal-ligand bond increases with the increase in atomic number which is in conformity with the lanthanide contraction.