Nano‐sized metal complexes of azo L‐histidine: Synthesis, characterization and their application for catalytic oxidation of 2‐amino phenol

Abstract

A novel azo dye ligand formed by the coupling of L‐histidine with 2‐hydroxy‐1‐naphthaldyhide(H2L) and its Ru3+, Pd2+ and Ni2+ nano‐sized complexes were obtained and described by elemental analysis, TGA, magnetic moment measurements, molar conductance, UV‐Vis, ESR, X‐ray powder diffraction, IR, SEM, TEM, 1H‐nmr, 13C‐nmr, and EI‐mass spectral studies. The analytical results and spectral studies detected that the H2L ligand acts as dibasic tetradentate via aldehyde oxygen, azo nitrogen and deprotonated OH and COOH groups. The data showed the paramagnetic Ru3+ complex has octahedral geometry while Pd2+ and Ni2+ have square planar structures. The molar conductance measurements display all complexes are nonelectrolyte. The crystallinity, morphology and average particle size data revealed the prepared complexes were formed in the Nano scale. The average particle size as calculated from TEM images are found to be 13.72, 64.52 and 115.00 nm for Ru3+, Pd2+ and Ni2+ chelates, respectively. The catalytic activities of these compounds were checked for oxidation of 2‐amino phenol to 2‐amino‐3H phenoxazine‐3‐one as heterogeneous catalysts. A 96, 31 and 21% catalytic conversion are found when using Ru(III), Pd(II) and Ni(II) complexes respectively.