Preparation of Non-heme {FeNO}⁷ Models of Cysteine Dioxygenase: Sulfur versus Nitrogen Ligation and Photorelease of Nitric Oxide

We present the synthesis and spectroscopic characterization of [Fe­(NO)­(N3PyS)]­BF4 (3), the first structural and electronic model of NO-bound cysteine dioxygenase. The nearly isostructural all-N-donor analogue [Fe­(NO)­(N4Py)]­(BF4)2 (4) was also prepared, and comparisons of 3 and 4 provide insight regarding the influence of S vs N ligation in {FeNO}7 species. One key difference occurs upon photoirradiation, which causes the fully reversible release of NO from 3, but not from 4.