The new, potentially ambidentate heterocyclic ligand
2,3-bis(1-methylimidazol-2-yl)quinoxaline (bmiq) was obtained from
2,3-bis(1-methylimidazol-2-yl)glyoxal and 1,2-diaminobenzene. Its coordination
to PtCl2 and to the isoelectronic [AuCl2]+ in [AuCl2(bmiq)](AuCl4) occurs via
the imine N donors of the imidazolyl groups, leading to the formation of
seven-membered chelate rings with boat conformation. According to the
spectroelectrochemistry (UV-vis-NIR, EPR), the reversible electron addition to
the [PtCl2(bmiq)] and the free ligand takes place in the (non-coordinated)
quinoxaline part of the molecule, similarly as for related complexes of
dipyrido[3,2-a:2′,3′-c]phenazines (dppz), 2,3-bis(2-pyridyl)quinoxalines (bpq)
and 2,3-bis(dialkylphosphino)quinoxalines (QuinoxP). DFT calculations confirm
the experimental results (structures, spectroscopy) and also point to the
coordination potential of the quinoxaline N atoms. The electron addition to
[AuCl2(bmiq)]+ takes place not at the ligand but at the metal site, according
to experimental and DFT results
