ELECTRON-PARAMAGNETIC-RESONANCE, ELECTRON-SPIN ECHO MODULATION AND ELECTRON NUCLEAR DOUBLE-RESONANCE STUDIES ON THE PHOTOIONIZATION OF N-ALKYLPHENOTHIAZINES IN CETYLTRIMETHYLAMMONIUM BROMIDE ALCOHOL REVERSE MICELLES - EFFECTS OF ALKYL CHAIN-LENGTH OF ALKYLPHENOTHIAZINES, REVERSEMICELLAR WATER POOL SIZE AND COSURFACTANT ALCOHOL

Neutral N-alkylphenothiazines (PC(n), n = 1, 3, 6, 9, 12, 16) are solu bilized and photoionized in cetyltrimethylammonium bromide (CTAB)-alco hol reverse micelles at 77 K to investigate the optimum photoionizatio n conditions by varying the cosurfactant alcohol, reverse micellar wat er pool size and pendant alkyl chain length. The photoproduced radical s are identified and quantified by electron paramagnetic resonance (EP R). The relative locations from deuteriated water at the interface are monitored by deuteron electron spin echo modulation (ESEM) and proton matrix electron nuclear double resonance (ENDOR). The photoyields and deuteron modulation depths of PC(n) compounds show a U-shaped trend w ith increasing pendant alkyl chain length which indicates U-shaped con formations for the longer alkyl chains. The photoyields of the PC(n) c ompounds decrease with the water to surfactant mole ratio and correlat e with decreasing deuteron modulation depths which indicate an increas ing distance from the phenothiazine moiety to deuteriated interface wa ter. The deeper penetration is attributed to a decreased packing densi ty of the interface region of the reverse micelles. This is supported by decreasing ENDOR linewidths with increasing water pool size. A chan ge of cosurfactant alcohol from butanol to octanol slightly decreases the photoyield and the deuteron modulation depths. This reflects deepe r solubilization and a decreased rate of photoinduced radical conversi on.