Tridentate benzimidazole ligand and its metal complexes: Synthesis,characterization, photo physical and sensor properties

A tridentate bisbenzimidazole-pyridine ligand (L-C⁵) with two pentyl side-units and its metal complexes with Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ metal ions were synthesized and characterized. The structures of the ligand (L-C⁵) and its five coordinate Mn(L-C⁵)Cl₂] were elucidated by single crystal X-ray diffraction studies. The absorption and photoluminescence properties of the compounds were studied in solution media. The ligand is highly fluorescent, and binding of the metal ions to the ligand has caused significant changes in the emission band (shift or quenching). Moreover, the effect of aggregation on UV–Vis. absorption and emission properties was examined in MeOH-water mixtures. The ligand was found to show aggregation-induced quenching in the MeOH-water mixture. The ligand was also screened for its colorimetric and fluorometric sensing ability of several metal ions Na⁺, K⁺, Mg²⁺, Al³⁺, Ca²⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Hg²⁺, Pb²⁺]. The ligand showed selective sensing ability towards Zn²⁺, and the limit of detection was calculated as 3.09 × 10^?7 m . The ligand also showed a distinguishable color change in the presence of Fe²⁺ under daylight.