# Computational Modelling of Imidazole Protection of Coordinated Gadolinium Tetraphenylporphyrine Against Molecular Oxygen Attack

## TL;DR

This paper uses computational modeling to show how imidazole protects a gadolinium porphyrin complex from oxygen.

## Contribution

The study demonstrates imidazole's protective role against oxygen attack in Gd(III)-tetraphenylporphyrin complexes using DFT calculations.

## Key findings

- Imidazole ligands protect the Gd(III)-porphyrin complex from molecular oxygen attack.
- Thermodynamic analysis shows complex formation is influenced by imidazole and side products.
- Electrostatic potential and structural parameters vary with different imidazole coordination numbers.

## Abstract

Promising photophysical properties and the enhanced sensitivity to molecular oxygen of porphyrins metalated with Gd(III) generate a need for their detailed description on an atomic level with the account of coordinated ligands, which also influence the properties. Herein, the complexation of tetraphenylporphyrin with gadolinium chloride in imidazole medium was analyzed using density functional theory in the framework of ωB97XD functional with hybrid diffused polarization-consistent basis sets. The complexes with different number of coordinated imidazole ligands (k = 0–2) were calculated to compare their structural parameters, electrostatic potential distribution, and interaction with molecular oxygen. Thermodynamic functions of complex formation were estimated for a set of possible reactions, including various side products (hydrogen chloride or imidazole hydrochloride) and different number of imidazole molecules involved. Weak interactions in the coordination sphere of chlorogadolinium tetraphenylporphyrin with attached imidazole ligands were also assessed. Performed analysis proved the presence of imidazole protection against the molecular oxygen attack.