Solvent Effect on the Absorption and Fluorescence Emission Spectra of Some Purine Derivatives: Spectrofluorometric Quantitative Studies

Journal of Solution Chemistry (Impact Factor: 1.08). 07/2008; 37(7):895-917. DOI: 10.1007/s10953-008-9289-8

ABSTRACT The absorption and emission spectra of six purine derivatives: adenine (I), N(9)-hydroxyethyladenine (II), N(6)-acetyladenine (III), N(6)-isobutyryladenine (IV), guanine (V), and N(2),N(9)-diacetylguanine (VI) have been investigated. The effects of solvent and pH on the positions of λ
max  (absorption) and λ
max  (emission) of these compounds were determined. Correlations between the absorption wavelength (λ
max ) of these organic compounds and the solvent parameters (D,n,E) or (K,M,N) show that the peak position is affected mainly by specific- and non-specific types of interactions between the solvent and
solute. Solvent effects on the electronic absorption band shifts are indicative of the extent of charge reorganization of
the solute molecules upon electronic excitation. The Stokes shift (ν
em) was correlated with the orientation polarizability (Δf) and was found to depend mainly on the dielectric constant and the refractive index of the solvents. This shift reflects
the influence of the equilibrium solvent arrangement around the excited solute molecule, which rearranges inertially due to
the instantaneous charge redistribution upon radiative deactivation to the electronic ground state. A spectrofluorometric
analysis technique was applied for the quantitative analysis of the components of a ternary mixture of compounds (I–III).

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