Synthesis, structure, catalytic and calculated non-linear optical properties of cis- and trans-, mer-chlorobis(triphenyl phosphine/triphenyl arsine)-dipicolinato ruthenium III complexes

Abstract

The new mononuclear Ru III complexes cis-, mer-[Ru( k 3-dipic)(EPh 3) 2Cl]·2H 2O (E = P ( 1), As ( 2)), (L = 2,6-pyridyldicarboxylate; dipic) have been synthesized and characterized. The X-ray crystal structure of 1 reveals that the coordination geometry around the Ru III center is distorted octahedral in which three sites are occupied by tridentate dipic ligand and remaining three sites are occupied by two mutually cis triphenyl phosphine ligands and one chloride ions. In chloroform solvent, cis-, mer-[Ru( k 3-dipic)(EPh 3) 2Cl]·2H 2O (E = P ( 1), As ( 2)) complexes undergoes thermal rearrangement to more stable trans-, mer-[Ru( k 3-dipic)(EPh 3) 2Cl] (E = P( 3), As( 4)) complexes. Complexes 1 and 2 show rhombic EPR spectral features, while complex 3 and 4 show tetragonal distortion. The new Ru III complexes 1 and 2 display both Ru III–Ru II reduction and Ru III–Ru IV oxidation processes. These geometric isomers exhibit textbook differences both in spectroscopic as well as structural properties in the solid state. The new complexes 1 and 2 were found to catalyze the oxidation of alcohols to carbonyl derivatives using N-methyl morpholine- N-oxide as co-oxidant. The first static hyperpolarizability ( β) for all of the complexes have been investigated by density functional theory (DFT) which suggests β value increases from trans to cis form. Also, the solvent-induced effects on the non-linear optical properties (NLO) were studied by using self-consistent reaction field (SCRF) method. As the solvent polarity increases, the β value increases monotonically. The electronic absorption bands of 1 have been assigned by time dependent density functional theory (TD-DFT).