Solvent Effect Studies on the Absorption and Fluorescence Spectra of Adenine, Thymine and Uracil Derivatives

Mild and efficient synthetic procedures were developed for the preparation of a series of adenine, thymine and uracil-derivatives in high yields. In this respect, four derivatives were derived by introducing various substituents flanked by two methylene groups at the 1- and 9- positions of pyrimidine and purine bases, respectively. The other two were prepared from 6-amino-1,3-dimethyluracil or 5,6-diamino- 1,3-dimethyluracil by diazotization or aldehyde condensation. The photophysical characterization in a number of organic solvents with diverse polarities and in aqueous solutions at various pH, have been subjected to multiple regression analysis with more than ten different solvent parameters. The effects of solvent polarity and hydrogen bonding on the absorption and emission spectra were interpreted in the light of theoretical predictions. The validity of the regression models has been established from the linearity of the calculated and observed transition energy relating to absorption spectra and Stokes shift. This deep investigation provides realistic depiction of solvent effects on absorption and emission spectral properties of nucleobase derivatives.