Physicochemical studies of bioactive heterocycles of some novel imidazole derivatives as sensitive NLO materials

Some novel imidazole derivatives were developed as highly sensitive chemisensors for transition metal ions. A prominent fluorescence enhancement was found in the presence of transition metal ions such as Hg2+, Pb2+, Cu2+, Zn2+, Co2+ and Fe2+ and this was suggested to result from the suppression of radiationless transitions from the n–π* state in the chemisensors. By DFT calculation HOMO–LUMO energies were calculated, the electric dipole moment (μ) and the hyperpolarizability (β) of the investigated molecules have been studied experimentally and also theoretically. These synthesized molecules were found to have microscopic non-linear optical (NLO) behaviour with non-zero tensor components.

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► Stokes shifted PL: Emission has originated from the when excited to S1 state.
► Quantum yield: Radiative rate constants (kr) increases as λemi max shift to red.
► Increase in ϕ in the presence of Cu2+ is due to decrease in non radiative transition.
► Non-zero dipole moment, hyperpolarizabilities have well microscopic NLO behaviour.
► Electronic properties: Probable charge transfer (CD) inside the chromophore.