Chemistry

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Tuning Fluorescence Properties of 2, 2′- biquinoline Using Metal Cation
(Addis Ababa Universty, 2011-06) Bezabih, Tewodros; Redi, Mesfin (PhD)
The steady state absorption, fluorescence excitation and emission spectra of 2, 2′- biquinoline have been studied in polar and non-polar solvents. Absorption spectra are almost independent of solvent polarity. The dependence of fluorescence emission on excitation wavelength was observed in acetonitrile, dichloromethane and p-dioxane but independent of excitation energy in cyclohexane. Addition of metal ion and varying pH of the solution shifted the absorption and excitation band to the red-edge. Corresponding excitation bands of the metal free conformers were compared to the stable conformers of metal-chelated and protonated 2,2′- biquinoline. Study of the rotational profile of 2, 2′- biquinoline at semi-empirical of INDO methods shows two energy minima corresponding to two conformations of different energy, cis/trans structures, with barrier to rotation comparable for trans to the room temperature thermal energy but less for cis conformer. It is shown that distributions of energetically different conformers of the molecule (cis/trans) in the ground state are responsible for the dual fluorescence behavior of the systems