Tuning Fluorescence Properties of 2, 2′- biquinoline Using Metal Cation
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Date
2011-06
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Addis Ababa Universty
Abstract
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
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2, 2′- biquinoline Using Metal Cation