Nitrosyliron complexes with mercapto-purines and -pyrimidines studied by nuclear magnetic and electron spin resonance spectroscopy

Abstract

The formation of dinitrosyliron complexes with mercapto-purines and -pyrimidines has been studied by e.s.r. and n.m.r. spectroscopy. The binding sites were established by the aid of computer-simulated spectra and of isotopic substitution with ¹⁵NO. The sulphur atom complexed with the iron only if ionized. Hindered tautomerism caused complexation via the imidazole nitrogen atoms in mercaptopurines. Two complexes were present at pH 7 in mercaptopyrimidines. A nine-line e.s.r. spectrum was attributed to a complex with two base molecules bonded to the iron atom, one via N-3 and the other via S^–. A quintet was attributed to a complex with two bases bonded via S^–.