Solvent effect on photophysical properties and Mg2+ binding of 1,3-diphenyl-propane-1,3-dione

The absorption and emission spectroscopic investigations of a β-diketone, 1,3-diphenyl-propane-1,3-dione (1k) in various polar, non-polar as well as protic and aprotic solvents are reported. The solvatochromic shifts of the spectral bands were studied in a multitude of solvents followed by multilinear regression in which several solvent parameters were simultaneously analysed. This π-conjugated β-diketone exhibits solvatochromism. Variation in the electronic absorption and emission spectral characteristics of 1k were studied in solution in presence of magnesium perchlorate. Absorption spectral studies indicate complex formation between magnesium ion and 1k in the ground state. The values of equilibrium constant, enthalpy and entropy of complex formation together with the molar absorbance of the absorbing species have been determined for the diketone–cation 1:1 interaction. Fluorescence spectral changes with the addition of Mg(ClO4)2 revealed the existence of hydrogen bonded excited state of 1k. The values of equilibrium constant for 1k/Mg2+ interaction have been measured in acetone and methanol media.