Phototransformations of substituted chalcones under conditions of direct and sensitized photolysis

The luminescence and absorption characteristics and photochemical propertie s in dimethylacetamide of chalcone derivatives R-1-C6H4-CH=CH-CO-C6H4-R-2 [ R-1 = H, p-OCH3, p-NHCOPh, p-SCH3, p-N(CH3)(2); R-2 = H, p-NHCOPh, m-NHCOPh , m-NO2] (a total of 13 compounds) and of phthalimides and polyamides conta ining the chalcone group in the backbone and pendant chains (six compounds) were studied. The quantum yields of the photoreaction of chalcones under c onditions of direct photoexcitation at various wavelengths (lambda 313, 334 , 366, 406 nm; air) varied from 0.28 to less than 10(-4), whereas under con ditions of sensitized photolysis (lambda 546 nm, Ar, erythrosine, triethano lamine) the quantum yields varied within 0.003-0.055. Phthalimide substitue nts in chalcone molecules inhibit both direct and sensitized reactions. The photochemical activity of polyamido imides is close to or considerably low er than that of phthalimides depending on the structure of the polymer unit and on photolysis type. The results were interpreted in terms of different mechanisms of the direct and sensitized photolysis, involving, respectivel y, trans-cis isomerization and dimerization, with participation of the T an d S-0 states of chalcone molecules.