Catecholase-Like Activity and Theoretical Study in Solid State of a New Ru(III)-Schiff Base Complex

Niladri Biswas,Sandeepta Saha,Chirantan Roy Choudhury,Antonio Frontera,Ennio Zangrando

doi:10.17344/acsi.2020.6379

Abstract

A new ruthenium(III) complex of molecular formula [Ru(PPh3)Cl2(L)] (1) has been synthesized using the Schiff base ligand obtained from 5-chlorosalicylaldehyde and N,N-dimethylethylenediamine, and characterized by FT-IR, UV-Vis, cyclic voltammetry and single crystal X-ray structural analysis. The metal ion exhibits a slightly distorted octahedral environment where the chelating Schiff base ligand contributes with its NNO donor set. The coordination geometry around the Ru(III) ion is completed by a PPh3 ligand and two chloride anions, and the charge balance is assured by the phenoxo oxygen of the Schiff base. With the aim to analyse the energy related to the halogen bonding interactions in solid state, a theoretical study has been performed on complex 1, by using the MEP and NCI plot computational tools, was also performed with the aim to analyse the energy related to the halogen bonding interaction. Furthermore, complex 1 shows catecholase-like activity in conversion of the model substrate 3,5-di-tert-butylcatechol (3,5-DTBC) to the corresponding 3,5-di-tert-butylquinone (3,5-DTBQ) under aerobic condition. The parameters regarding the enzymatic kinetics have been evaluated from the Lineweaver-Burk plot using the Michaelis-Menten approach of enzyme catalysis. A significant high T.O.N value (2.346×103 h-1) indicates that complex 1 has a very good catalytic efficiency towards 3,5-DTBC.

Highlights

In last decade, coordination chemistry of transition metal ions with Schiff bases has evolved as an an area of active research.[1,2] Schiff bases affect electronic factors of the metal centres, stabilizing different oxidation states, address the performance of complexes, which can acquire a variety of suitable properties like that to act as homogeneous and/or heterogeneous catalysts.[3,4,5,6] design of metal complexes having catalytic activity may be helpful to elucidate the mechanistic aspects of biochemically important metalloenzyme reactions
The coordination geometry around the Ru(III) ion is completed by a PPh3 ligand and two chloride anions, and the charge balance is assured by the phenoxo oxygen of the Schiff base
With the aim to analyse the energy related to the halogen bonding interactions in solid state, a theoretical study has been performed on complex 1, by using the molecular electrostatic potential (MEP) and NCl plot computational tools

Summary

Introduction

Coordination chemistry of transition metal ions with Schiff bases has evolved as an an area of active research.[1,2] Schiff bases affect electronic factors of the metal centres, stabilizing different oxidation states, address the performance of complexes, which can acquire a variety of suitable properties like that to act as homogeneous and/or heterogeneous catalysts.[3,4,5,6] design of metal complexes having catalytic activity may be helpful to elucidate the mechanistic aspects of biochemically important metalloenzyme reactions. The energy barrier for the oxidation state change from Ru(III) to Ru(II) inside the cell is very low and due to the larger coordination number with respect to platinum-(II), ruthenium-(III/II) can form complexes with a number of elements having different electronegativity as well as chemical hardness.[11,12,13,14] Till date, there are plenty of reports on Ru(II/III) compounds with bidentate ligands but design of such complexes with somewhat more rigid, tridentate Schiff bases ligands are rarely found.[15]

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Results

Conclusion