Abstract
Dinitrosyl iron complexes (DNICs) are the most abundant nitric oxide (NO) metabolites in NO-producing cells and can be used as a platform for photochemical vehicles for NO donors. However, not much is known about the photochemical dynamics of DNICs. This study investigates the photoexcitation dynamics of a mononuclear DNIC ligated with 2-mercaptoethanol, [(HOCH(2)CH(2)S)(2)Fe(NO)(2)](-), in D(2)O solution through femtosecond infrared spectroscopy. Approximately 70% of the excited [(HOCH(2)CH(2)S)(2)Fe(NO)(2)](-) at 400 nm relaxes back to the ground state with a time constant of 270 ps, and the remaining dissociates NO(-) with a time constant of 630 ps. The resulting mononitrosyl iron complex, [(HOCH(2)CH(2)S)(2)Fe(NO)(D(2)O)(2)], formed by a rapid coordination of D(2)O molecule to the nascent photoproduct, [(HOCH(2)CH(2)S)(2)Fe(NO)], reacts with the abundant thiolate, HOCH(2)CH(2)S(-), in solution, producing [(HOCH(2)CH(2)S)(3)Fe(NO)](-) with a rate constant of 1.3 × 10(7) M(-1)s(-1). The detailed photochemical dynamics described herein lays the groundwork for the development of NO(-) donors using DNICs with controlled and tunable photoreactivity for potential therapeutic applications.