Ab initio molecular dynamics study of manganese porphine hydration and interaction with nitric oxide

TL;DR

This study uses ab initio molecular dynamics and DFT+U to explore how manganese porphines interact with water and nitric oxide, revealing differences in hydration and NO displacement behavior relevant to biological and electrochemical systems.

Contribution

It provides detailed computational insights into the hydration environments and NO interactions of manganese porphines, advancing understanding of their physiological and electrochemical roles.

Findings

Mn(II)P binds strongly to a single water molecule with significant out-of-plane displacement.

Mn(III)P forms a stable complex with two water molecules, each with residence times over 15 ps.

DFT+U predicts water displaces NO from Mn(III)P-NO but gives ambiguous spin states for Mn(II)P-NO.

Abstract

The authors use ab initio molecular dynamics and the density functional theory+U (DFT+U) method to compute the hydration environment of the manganese ion in manganese (II) and manganese (III) porphines (MnP) dispersed in liquid water. These are intended as simple models for more complex water soluble porphyrins, which have important physiological and electrochemical applications. The manganese ion in Mn(II)P exhibits significant out-of-porphine plane displacement and binds strongly to a single H2O molecule in liquid water. The Mn in Mn(III)P is on average coplanar with the porphine plane and forms a stable complex with two H2O molecules. The residence times of these water molecules exceed 15 ps. The DFT+U method correctly predicts that water displaces NO from Mn(III)P-NO, but yields an ambiguous spin state for the MnP(II)-NO complex.