Structure, photodynamic reaction and DNA photocleavage properties of a nitrosyl iron-sulfur cluster (Me4N)2[Fe2S2(NO)4]: A DFT calculation and experimental study

Density functional theory calculationswere performed on the structure of the nitrosyl iron-sulfur cluster (Me4N) (2)[Fe2S2(NO)(4)]. The IR spectrawere assigned and the electronic ground-state properties in different solvents were analyzed. Dynamic conversion of [Fe2S2(NO)(4)](2-) was analyzed quantitatively using the time-resolved IR spectra in different solvents. Photo irradiation and polarity of solvent obviously affect the reaction rates, which are faster in CH3CN and CH3OH than those in DMSO and water. The calculated orbital energies of HOMOs are higher and those of LUMO-HOMO gap are smaller in CH3CN and CH3OH than those in DMSO and water, which is consistent with the reaction rate and explains the experimental observation. Moreover, the photo-induced nitric oxide (NO) release and cluster conversion was identified using EPR spectra. The photocleavage of pBR322 DNA was observed, both NO and oxygen related free radicals play key roles in the process. The study provides an effective method to monitor the photodynamic reactions for better understanding of the physiological activity of nitrosyl iron-sulfur clusters. (C) 2020 Elsevier B.V. All rights reserved.