Formation of dinuclear, macrocyclic, and chain structures from Hgl2 and a semirigid benzimidazole-based bridging ligand:: An example of ring-opening supramolecular isomerism

The reactions of Hgl(2) with the semirigid ditopic ligand 1,3-bis(benzimidazol-1-yl methyl)-2,4,6-tri methyl benzene (bbimms) afforded three new complexes, [Hg2(mu-l)(2)l(2)(bbimms)] (1), [Hg(2)l(4)(bbimms)(2)] (2), and catena-poly[Hgl(2)(bbimms)] (3). The ligand and all complexes have been structurally characterized by single-crystal X-ray diffraction. 1 is a triply bridged dinuclear complex comprised of two Hg(II) ions, one bridging ligand, two bridging I- anions, and two terminal I- anions. 2 is a dinuclear metallamacrocycle comprised of two Hg(II) ions, two bridging ligands, and four terminal I- anions, while 3 is a helical chain with the repeating unit of Hgl(2)(bbimms). 2 and 3 can be classified as supramolecular isomers, and both are related to the triply bridged precursor 1 via the addition of one more ligand in a ring-opening process.