Synthesis and photophysical studies of a new benzimidazole derivative and its zinc(II) complexes

The photochemical and photophysical properties of the new ligand N-[2-(5,6-dihydrobenzimidazo[1,2-c]quinazoline-6-yl)phenyl]-4-methylbenzolsulfamide (1) and its zinc complexes, namely [2-[(E)-[2-(1H-benzimidazol-2-yl)phenyl]iminomethyl]-N-(p-tolylsulfonyl)anilino]chloro-zinc (3) and acetoxy-[2-[(E)-[2-(1H-benzimidazol-2-yl)phenyl]iminomethyl]-N-(p-tolylsulfonyl)anilino]zinc (4) were studied using UV spectroscopy, time-resolved luminescence and stationary photolysis. Compound 1 combines the properties of Schiff bases and benzimidazole derivatives, both known as good luminophores. The structures of compounds in the crystalline state were determined by means of XRD. Ligand 1 demonstrates high photoluminescence quantum yields (PLQY) in solutions, while for the soluble zinc complex 3 it drops in an order of magnitude. PLQY in the solid state for all the compounds are moderate (0.2-0.3). For complex 3 the PLQY in the solid state is ca. 3 times higher than in solutions, demonstrating the effect of aggregation-induced enhancement of luminescence. The approach based on combining properties of the two classes of luminophores seems prospective for further development of luminescent materials.