Photoinduced electron transfer between cytochrome c and a novel 1,4,5,8-naphthalenetetracarboxylic diimide with amphiphilic character

N-dodecyl-N′-(2-phosphonoethyl)-1,4,5,8-naphthalenetetracarboxylic diimide (DNDI) is a novel naphthalenic diimide with amphiphilic character. DNDI was synthesized through the sequential reaction of 1,4,5,8-naphthalenetetracarboxylic dianhydride, first with dodecylamine and then with 2-aminoethylphosphonic acid. Fluorescence measurements showed that DNDI forms excimers in water at sufficiently high concentrations. The fluorescence quantum yield of DNDI in diluted solutions is sensitive to the polarity of the microenvironment, decreasing as going from water to less polar solvents. This property allowed to monitor the incorporation of DNDI into cetyl trimethyl ammonium bromide (CTAB) micelles, with a binding constant of 1.2 × 104 M−1. UV irradiation (365 nm) of solutions containing DNDI and the redox protein cytochrome c (cyt c) resulted in the reduction of the heme iron from the Fe(III) to the Fe(II) state, a reaction that was inhibited by the incorporation of DNDI into CTAB micelles. DNDI formed host–guest complexes with α-cyclodextrin (α-CD) through the inclusion of the dodecyl group, resulting in an increased aqueous solubility of the compound.