Spectroscopic characterization, structural investigation, DFT study, and Hirshfeld surface analysis of rhodium and ruthenium amido azo complexes

Abstract

The reaction of 2,2′-diaminoazobenzene, (H2L) [where H represents the dissociable amino protons], with RhCl3 and Ru(dmso)4Cl2 separately afforded the new homoleptic mononuclear amido azo complexes [Rh(HL)2]Cl (1) and [Ru(HL)2](ClO4)2 (2), respectively. Complex 1 & 2 were characterised by spectroscopic technique and confirmed by x-ray structure determination. Both the complexes, the ligand coordinates meridionally to the metal centre (Rh & Ru) through amido-N, azo-N, and amine-N via single NH deprotonation to form five- and six-membered chelate rings. Solid-state x-ray structure of compounds 1 and 2 revealed an approximately octahedral environment about metals. Both the complexes are twofold crystallographically imposed symmetry with the metals (Rh & Ru) atom in a distorted octahedral environment consisting of six nitrogen atoms from two ligand molecules. In the crystals of [Rh(HL)2]Cl, characteristic networks are built up by πCH—Cl stacking and/or hydrogen bonding interactions between amino nitrogen of complex cations with counter chloride anions. The chain like crystal structures of [Ru(HL)2](ClO4)2 are stabilized by the direct hydrogen-bonding networks between amino (NH2) and amido (NH) nitrogen atoms complex cations with perchlorate anions. Redox properties of the new complexes are examined. DFT calculation were performed to calculate the energy gaps between different orbitals and to correlate the bond lengths and bond angles of complex 1 and 2 with experimental data. Hirshfeld surface analysis and two dimensional finger print plots were performed to describe the intermolecular interactions along contact contribution in the crystalline molecules.