PHOTODIMERIZATION OF CINNAMIC-ACIDS CONTROLLED BY MOLECULAR ASSEMBLIES OF SURFACTANT AMINE N-OXIDES

UV irradiation of cinnamic acids 1 involving a complex with surfactant amine N-oxides (C(n)DAO, n = 12, 14 and 16) as vesicles in water lead s to the formation of cyclodimers (i.e. beta-, delta-truxinic and/or a lpha-truxillic acids dagger). Decreasing the molar ratios of 1 to C(n) PAO causes the vesicles to transform into rod-like micelles and the yi eld of the cyclodimers decreases. The addition of HCl or NaOH to aqueo us solutions of 1 and C(n)DAO brings about sharp changes in the self-a ssembly structures from vesicles to micro emulsions or rod-like micell es, accompanied by a change in product distribution in the photolysis of the complex 1. Upon addition of photoinactive carboxylic acids, phe nylpropionic and palmitic acids to the 1 and C(16)DAO system, the rod- like micelles change into vesicles by formation of a complex with C(16 )DAO leading to the observation of a dilution effect in the photodimer ization upon addition of phenylpropionic acid. However, no dilution ef fect is observed for the palmitic acid. This is found to be attributab le to the difference in degrees of mixing of 1 with the acids in the v esicles. These results show that photodimerization of 1 incorporated i n C(n)DAO is controlled by a variety of molecular assemblies, i.e. rod -like micelles and homogeneous or heterogeneous vesicles.