METAL-LIGAND BONDING SITUATION IN RUTHENIUM NITROSYL COMPLEXES CONTAINING POLY(PYRAZOLYL)BORATE LIGANDS

Abstract

Purpose: Nitric oxide (NO) plays a crucial role in physiological processes such as blood pressure regulation, neurotransmission, induction of apoptosis, among others. In this way, the synthesis of new organometallic compounds containing NO, such as nitrosyl ruthenium complexes, has been studied, since these complexes can not only scavenge but also to regulate the NO-level in vivo . In order to contribute to the comprehension of Ru−NO bonding, the present work investigated different complexes containing poly(pyrazolyl)borate (Tp) as ligands. Methods: The nature of the chemical bonds was evaluated at the light of EDA-NOCV method (Energy Decomposition Analysis - Natural Orbitals for Chemical Valence) using nonlocal DFT ( Density Functional Theory - BP86 functional) level of theory. Results: The results showed that the Ru(II)-NO + bonding have a predominantly covalent character (70% of the total interaction energy), whereas about 30% is derived from the electrostatic interactions. The density deformation channels indicate that the contribution to the covalent character is due to the one σ donation ligand ® metal and two π backdonation metal ® ligand. The BCP (Bond Critical Point) properties obtained by the QTAIM (Quantum Theory of Atoms in Molecules) analysis also suggest a partially covalent character for the Ru(II)-NO + bonding. Conclusion : The analyzes allow to conclude that the addition of different substituent groups, especially electron withdrawing groups such as -CHO and -NO 2 , groups may lead to the decrease of the Ru(II)-NO + interaction energy, which can be important for controlled release mechanism of nitric oxide.