have been synthesized via the reactions of FeSO 4 and Na 2 [Fe 2 (S 2 O 3 ) 2 (NO) 4 ], respectively, with acidic solutions of thiocarbamide in water. The structure and properties of I and II were studied using X-ray analysis, Mössbauer, IR, and EPR spectroscopy and amperometry. Both complexes are characterized by a prolonged NO generation without additional activation in aqueous anaerobic solutions, similar to the organic NO donor diethylene triamine; however, they are more effective: at pH 7 the NO amount is B32.6 and B31.8 nM mol À1 of the complex for I and II, respectively. The obtained results show feasibility for the synthesis of water-soluble hybrid nitrosyl NO-generating complexes, which contain the NO groups both in the cationic and anionic sublattices and provide the control of the NO release kinetics.