(E)-2-Benzylidenecyclanones: Part VI. Solvent effect on the UV and fluorescence properties of some chalcones and their cyclic analogues. Interaction of 4-dimethylaminochalcones with bovine and human serum albumin: a UV-vis study

UV-vis and fluorescence spectroscopic investigations of chalcones and cyclic chalcone analogues, (E)-2-(4-X-benzylidene)-1-indanones, -tetralones, and -benzosuberones with the same substitution patterns were performed in solvents with different polarity. Comparison of position of the absorption maxima of three substituted series (unsubstituted, methoxy, and dimethylamino) showed the same decreasing order indanones >= chalcones >= tetralones >= benzosuberones in each solvent indicating the strongest conjugation of the rigid, planar indanones. All the compounds showed positive solvatochromism, which is consistent with transitions having significant charge transfer character. The order of the observed solvent-induced bathochromic shifts of the absorption maxima was found to correlate with the donor number of the solvents. The solvent-induced shift of the emission maxima of each compound is larger than that of the absorption maxima. Recording the UV-vis spectra of the compounds in the presence of bovine and human serum albumin resulted in a slight hypsochromic shift of (E)-2-(4-methoxybenzylidene)- and (E)-2-[(4-dimethylamino)benzylidene]benzosuberone indicating changing the polar environment to a less polar one. Such an observation is in accord with an interaction of the molecules with the hydrophobic binding site(s) of the two proteins.