Dicopper(II) MozobilTM: a dinuclear receptor for the pyrophosphate anion in aqueous solution.

In this work, we investigated the dicopper(II) complex of MozobilTM as a potential receptor for anions in MeOH and MeOH/water mixture. The results were compared with those obtained for the mononuclear complex, copper(II) benzyl-cyclam as a model system. Experimental investigations were also supported by computational studies on both the dinuclear and the mononuclear species. Among the investigated anionic guests, the dicopper complex showed an outstanding affinity for the pyrophosphate anion, leading to the formation of a stable adduct in MeOH solution. Our computational studies strongly suggested a 2:2 stoichiometry for the adduct. At least in MeOH, this dimeric structure, with two pyrophosphate anions sandwiched between two dicopper MozobilTM units, is stabilized by H-bonding interactions between the receptor and pyrophosphate. In MeOH:water mixture, beside the strong competition of solvent, the affinity toward the anion was preserved. We exploited this property to develop a novel indicator displacement assay (IDA) for pyrophosphate in aqueous solution, using Pyrocatechol Violet (PV) as the indicator.