Influence of metal-ligand ratio on benzimidazole based luminescent lanthanide complexes: 3-D network structures and chloride anion binding

Reaction of LnCl(3)center dot 6H(2)O with the benzimidazole based ligand 2-(1H-benzoimidazol-2-yl)-4-bromo-6-methoxy-phenol (HL) in EtOH or MeOH under reflux gave dinuclear complexes of formula [Ln(2)(HL)(2)Cl-6(solv)(4)] (solv = EtOH or MeOH) with a ligand : metal ratio = 1 : 1 (Ln = Tb(1); Er(2); Gd(3); Yb(4)). A ligand : metal ratio of 2 : 1 under similar conditions gave the mononuclear complexes [Eu(HL)(2)Cl-3(MeOH)] (5) and [Ln(HL)(2)(H2O)(4)]center dot 3Cl (Ln = Er(6); Yb(7)). A ligand : metal stoichiometry of 4 : 1 gave complexes [Ln(HL)(4)H2O]center dot 3Cl (Ln = Nd(8); Gd (9); Eu(10)). The compounds have been structurally characterized by single crystal X-ray diffraction studies and their photophysical properties investigated.