Metal complexes of indole-3-acetic acid: synthesis, crystal structures, and Pb2+ chemosensing by cation-exchange reaction

Two binuclear complexes [Cu2(IA)4(DMSO)2]·CH3OH (1), [Cd2(IA)2(phen)2I2] (2), and one 1-D {[Pb2(IA)4]·CH3OH}n (3) (IAH = indole-3-acetic acid, phen = 1,10-phenanthroline) have been prepared and characterized by single crystal X-ray diffraction. Both 1 and 2 are binuclear wherein the central Cu ions are bridged by IA in 1, while Cd ions are bridged by I− in 2. Complex 3 has a 1-D chain structure based on secondary building units (SBUs) of [Pb2(IA)4]. The three complexes show strong fluorescence emissions, and chemosensor behaviors for metal cations are investigated in mixed DMF/H2O (1 : 9 v/v) solvent. The results reveal that 2 shows effective sensing to Pb2+. The mechanism of the detection to Pb2+ can be attributed to cation-exchange reaction between cadmium and lead ions.