Coordination of reduced Schiff base anion to Pd(II): Synthesis,characterization, DFT calculation and catecholase activity

The article reports the synthesis and characterization of a new palladium(II) complex of type (L_NNN^1?)PdCl] (1) where L_NNN^1? is a mono anionic Schiff's base having a imine bond in reduced state. The L_NNN^1? is generated from a tridentate NNN donor ligand (L_NNN) through in-situ reduction using sodium borohydride, where L_NNN is (E)-N-(phenyl(pyridine-2-yl)methylene)quinoline-8-amine)]. 1 is characterized by the single crystal X-ray diffraction study, IR, mass and UV–Vis spectroscopy. The X-ray bond parameter authenticates the imine bond of the coordinated Schiff's base anion is in reduced state. 1 exhibits catalytic activity towards the oxidation of 3,5-ditertiarybutyl catechol(3,5-DTBC) with turnover number (K_cat) ?= ?135.6 h^-1. The catalytic oxidation of 3,5-DTBC is authenticated by the UV–Vis, mass and EPR spectroscopy. An isotropic EPR signal with g ?= ?2.011 of a solution containing 1 and 3,5-DTBC authenticating the generation of organic radical during the oxidation process. Cyclic voltammogram of 1 displays an irreversible anodic wave at +0.22 ?V may be due to the oxidation of N^? to N^??. The atomic spin density of 1⁺ obtained from DFT calculation is also supporting the N-centre oxidation process.