Reactivity of monohydrogensulfide with a suite of pyridoxal-based complexes: A combined NMR, ESI-MS, UV-visible and fluorescence study

摘要

In the present work, we explored the reactivity of HS- with a family of fluorescent metal complexes via a variety of spectroscopic techniques. The complexes under investigation are obtained by complexation of zinc or nickel with pyridoxal-based ligands. More specifically complexes 1 and 2 are zinc complexes namely L1 Zn(II) and L2Zn(II) where L1 stands for N,N'-phenylenebis(pyridoxyliminato) and L2 is N,N'-binaphthylenebis(pyridoxyliminato), whereas complex 3 is a nickel complex (L3Ni(II)) where L3 is N,N'-ethylenebis(pyridoxyliminato). A combination of NMR, ESI-MS, UV-vis and fluorescence experiments provide evidence that HS- binds the metal center in the case of complexes 1 and 3 whereas for complex 2, ZnS precipitation and hydrolysis of the organic ligand occur. Fluorescence experiments indicate that in the presence of HS- complex 1 undergoes a consistent fluorescence enhancement whereas for complex 3 the parent fluorescence exhibits a visible quenching. The results highlight the potential of complex 1 to be implemented as a HS- fluorescent sensor via a coordinative-based approach.