PHOTOIONIZATION OF NEUTRAL AND POSITIVELY CHARGED ALKYLPHENOTHIAZINES IN POSITIVE, NEUTRAL, AND NEGATIVELY CHARGED VESICLES - EFFECTS OF THE ALKYL CHAIN-LENGTH

The photoionization of alkylphenothiazines in vesicles of different surface charge was studied by electron spin resonance (ESR) and electron spin echo modulation (ESEM) methods. Neutral alkylphenothiazine (PC(n), where n = 2, 6, 12) and positively charged (alkylphenothiazinyl)trimethylammonium bromides (PC(n)TAB, where n = 4, 8, 12) were synthesized and used to study the effects of the alkyl chain length and the charge on the alkylphenothiazine derivative. In dioctadecyldimethylammonium chloride (DODAC) vesicles with a positive surface charge the photoionization yield of PC(n)TAB decreases as a function of chain length, while in negative dihexadecyl phosphate (DHP) and neutral dipalmitoylphosphatidylcholine (DPPC) vesicles the alkyl chain length had little effect. The magnitude of the photoyields measured by ESR decreased in the order DODAC > DPPC > DHP. For the neutral PC(n) compounds the photoyield decreased as a function of alkyl chain length for all systems. The magnitude of the photoyields for these systems was found to be in the order DODAC > DPPC > DHP. The ESEM data were consistent with these findings. The results are discussed in terms of the alkyl chain length, the charge of the alkylphenothiazine derivative, and the vesicle surface charge.