Pyrazole and Benzimidazole Derivatives: Chelating Properties Towards Metals Ions and their Applications

Due mainly to their structural diversities, pharmacological, electrochemical, and photophysical properties, the metal synthesis pyrazole and benzimidazole complexes were extensively designed and developed. The nitrogen-containing ligands playing an important role in coordination chemistry contain a wide variety of heterocyclic systems possessing one or more nitrogen atoms as electron donors, such as pyridine, isoxazole, pyrazole, 1,2,4- triazole, 1,3,5-triazine, quinoline, quinoxaline and benzothiazole. The structure of all ligands and the corresponding metal complexes are established using elemental analysis, infrared spectroscopy, NMR spectroscopy, mass spectrometry, single-crystal X-ray diffraction, thermogravimetric differential thermal analysis, static, magnetic susceptibility measurements, electron paramagnetic resonance spectroscopy (EPR), UV-Vis spectroscopy, and conductivity measurements.In this review, we report the synthesis and the chelating reactions of several heterocyclic ligands with various metals such as transition metals and lanthanides. The photophysical and photochemical properties of the metal complexes will also be presented and discussed.