Self-assembly of quaterpyridine ligands and Cu+ cations into helical complexes of 2:2 stoichiometry under electrospray ionisation conditions

摘要

Solutions containing the quaterpyridine ligand 1 and Cu2+ cation were analysed by electrospray ionisation mass spectrometry [ESI-MS]. It was found that copper reduction under ESI conditions and self-assembly of 1 and Cu(I) led to the formation of the 2:2 stoichiometry complex. Such stoichiometry is characteristic of the helical complex of a quaterpyridine ligand with Cu(I). The isotope pattern characteristic of the [Cu(2)1(2)](2+) ion, which is different from that of [Cu1](+) ion, is observed. When using methanol as the solvent, only [Cu(2)1(2)](2+) ions are observed in the mass spectrum obtained at tow cone voltage. At higher cone voltage, the [Cu(2)1(2)](2+) ion easily dissociates, producing a [Cu1](+) ion. When using other solvents studied, water and acetonitrile, the 2:2 stoichiometry complex is formed, but along with complexes of other stoichiometries. The helical complex was not observed for the silver cation for which only a 1:1 stoichiometry complex was observed (ion [Ag1](+)).