SOLVENT AND pH EFFECTS ON UV ABSORPTION SPECTRUM OF 1,3-bis[(3-(2-pyridyl) pyrazol-1 ylmethyl)] benzene (1,3-PPB)

The effect of single and binary solvents on electronic absorption spectra of 1,3-bis[(3-(2-pyridyl) pyrazol-1 ylmethyl)] benzene (1,3-PPB) was examined. 1,3-PPB has two absorption maxima (250 and 280 nm) due to pyridyl pyrazole and benzene systems. In order to explain the obtained results, UV absorption frequencies of the electronic transitions were correlated using a total solvatochromic equation by the Kamlet and Taft. The multiparametric analysis indicates that hydrogen bond donor ability of the solvent (for band I) and non-specific dipolar interactions of the solvents (for band II) play an important role in absorption maxima in pure solvents. Preferential solvation by ethanol (for two bands) was detected in i-PrOH-EtOH solvent mixture. Two spectrophotometric graphical methods were used to estimate the dissociation constant (pKb) with resulting average value of 10.12±0.41.