Interaction of 2-(2 '-pyridyl)benzimidazolyl derivative ligands with group 12 metal ions: coordination, structures and luminescence

The coordination chemistry of the group 12 metal ions with two 2-(2'-pyridyl)benzimidazolyl derivative ligands 1,3,5-tris[2-(2'-pyridyl)benzimidazolyl]benzene(tmb) and 2-(2'-pyridyl)benzimidazolylbenzene (mb) has been investigated. The crystal structures of two coordination compounds (HgCl2)2(tmb) (1) and [Zn(mb)(2)(H2O)][ClO4](2) (2) have been determined by single-crystal X-ray diffraction analysis which established the chelate bonding mode by the group 12 metal ions to the tmb or mb ligand. The luminescent response of tmb and mb toward group 12 metal ions, Zn(II), Cd(II) and Hg(II) has been examined by fluorescent titration experiments which established that the three group 12 metal ions have distinct luminescent response toward the tmb or mb ligand. The addition of the Hg(II) ion resulted in fluorescence quenching. In contrast, the addition of Zn(II) or Cd(II) led to a red shift and dramatic intensity increase of the emission spectrum of the ligand.