Synthesis, characterization, and nitrite reductase activity of Ni(II) complexes

Abstract

In biological systems, different types of nitrite reductase (NiRs) and nitric oxide synthase (NOS) isozymes are present to generate NO for physiological activities. To mimic this function, we choose the acid-induced path to reduced nitrite for nickel-nitrite metal complexes. In this study, we utilized the (BimH)3 ligand framework and synthesized three different complexes, namely [(BimH)3NiII(μ-Cl)2NiII(BimH)3]Cl2 (1), [(BimH)3NiII(L1)(L2)][NO3]2 (2), and [(BimH)3NiII(κ2O2NO)](NO3) (3). These complexes are characterized by different methods such as 1H, ESI-MS, SCXRD, UV-Vis, FT-IR. 2 and 3 are used to synthesis a main precursor [(BimH)3NiII(κ2-ONO)][NO3] (4) complex. Acid induced reduction of 4 leads to detachment of nitrite from the nickel sites as evident from the disappearance of the nitrite band in the FTIR. ESI-MS spectra reveals the formation of 2,5-di-tert-butylcatechol which is an indirect evidence of the homolytic N-O bond cleavage upon protonation.