Synthesis of dinitrosyl iron complexes (DNICs) with intramolecular hydrogen bonding

HSCH2CONHCH3 and HSCH2CON(CH3)2 containing a peptide bond are prepared for the synthesis of DNICs with/without intra-molecular hydrogen bonding, respectively. The IR ν(NO) bands of [(NO)2Fe(SCH2CONHCH3)2]− (2) appears at 1751, 1700 cm−1. In complex 2, the presence of intramolecular [NH⋯S] hydrogen bonding was verified by the observation of IR spectroscopy with N−H stretching frequency 3334 cm−1 (CDCl3) and subsequently confirmed by single-crystal X-ray diffraction showing N−S distance of 2.94 Å. Complex 2 displays the rhombic EPR spectrum with g1 = 2.039, g2 = 2.031 and g3 = 2.013 at in frozen H2O. Complexes 2 and 3 rapidly release NO when exposed to light. The time needed for photolysis reactions of 2 is two times faster than that of 3 in less polar solvent. Representative time courses for the photolability of 2 and 3 in THF display the NO-off ability: 2 > 3.