Photophysical characterization of low-molecular weight organogels for energy transfer and light harvesting

The choice of a donor and an acceptor with suitable optical and self-assembly properties is essential in the design of organogel-based light harvesting systems. Organogels can provide supramolecular structures capable of enhancing energy transfer processes. In this work, we present the characterization of N-(naphthalene-1-carboxyamide)-(3S,4S)-pyrrolidin-(3,4)-bisdodecyl-carbamoyldiester (1) and N-(4-nitrobenzofurazan-7-amino)-(3S,4S)-pyrrolidin-(3,4)-bisdodecyl-carbamoyldiester (2) which are used as donor and acceptor moieties, respectively. The donor molecule is hardly capable to form a gelon its own but it can be assembled at reasonable concentrations with the acceptor gelator to form a twocomponent donor–acceptor organogels in cyclohexane. Stable organogels are formed from cyclohexane for gelator concentrations as low as 10-3M. UV–vis and steady-state fluorescence spectroscopies were used to provide a characterization of their molecular interactions. The optical changes observed during the cooling of two-component solutions of these systems are indicative of typical sol–gel transitions.The occurrence of excitation energy transfer processes in the gels is confirmed by comparison of their excitation and absorption spectra.