Photochemistry of the (Fe(CN)_5NO)~(2-) -thiolate system

摘要

The studied system consists of [Fe(CN)_5NO]~(2-) 1, mercaptosuccinate or another thiolate (RS~-) and [Fe(CN)_5N(O)SR]~(3-) 2 in equilibrium. The photochemical study has shown that both complexes 1 and 2 undergo either photooxidiation or photoreduction, depending on the excited state energy. The present study is focused on the low energy effects, which consist of an inner-sphere photooxidation mode followed by a substitution pathway yielding pentacyanoferrate (III) complexes and NO or NOSR~(- centre dot) radicals for 1 and 2, respectively. In the presence of mercaptosuccinate the [Fe~(III)(CN)_5SR]~(3-) complex 3 and nitrosomercaptosuccinate were identified as the most stable products. The photochemical reactivity of the [Fe(CN)_5N(O)SR]~(3-) complex thus resembles the photooxidation-substitution mode characteristic of [Fe(CN)_5NO]~(2-) but produces nitrosothiol instead of NO and needs considerably lower energy to be induced (MLCT band at #lambda#_(max) 526 nm). Consequently, the photoreactivity of 2 creates the possibility of using the 1-RS~- system to photogenerate a nitrosothiol in situ using non-hazardous radiation.