Photophysical studies of diazines: effects of solvents and complexation with Cu2+, Ni2+, Co2+ and Pb2+ ions

Abstract

The detection of toxic metal ions, such as Pb²⁺, has become important because they cause several health issues. This study describes the photophysical properties displayed by a few symmetrical diazine compounds and the influence of solvent polarity on their emission spectra. It is noted that λ_em increases with an increase in the polarity of the solvent. The study of the complexation of diazine compounds with metal ions, such as Cu²⁺, Ni²⁺, Co²⁺ and Pb²⁺, shows that the coordination of the metal ions to the diazine molecule induces a blue shift in the UV-visible absorption spectrum. Among the studied compounds, compound 1 exhibited the maximum emission (λ_em) in hexane at 309 nm, with a maximum quantum yield (Φ_em) of 0.0576. The metal interaction study shows that the absorption intensity of compound 1 reached the maximum for Pb, indicating that the synthesized diazine could serve as a potential molecule to detect Pb²⁺ ions. The experimental results were further supported by computational studies, and the experimental data were in good agreement with the theoretical data. The TDDFT study shows that for all the compounds, the λ_abs corresponds to the HOMO−1 to LUMO+1 transition.