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The photochemistry and photophysics of a series of stilbene-functionalized fatty acids (SFA) have been examined in homogeneous solutions, supported Langmuir-Blodgett assemblies, and as guests in pliospholipid bilayers and micellar dispersions. The spectroscopic characteristics of stilbene-functionalized derivatives of pliosphatidyl choline (SFA-PC) have also been examined in organic solvents, aqueous dispersions and aqueous solution containing an excess of dipalmitoyl choline (DPPC), as well as in aqueous-methanol solutions containing V-cyclodextrin. Langmuir-Blodgett assemblies of individual SFAs, as well as mixtures of various SFAs, exhibit spectroscopic properties (blue-shifted absorbance and red-shifted fluorescence relative to those observed in organic solvents) consistent with the formation of an "H" aggregate. The same effect is observed for SFA-PCs in aqueous dispersions and in aqueous-methanol solutions containing 3,-cyclodextdn. The "H" aggregate is found to be the preferred geometric orientation of the Btilbene chromophores which may correspond to an energy minimum for the systems investigated. Preliminary studies with SFA-PC in methanol-water solutions containing y-cyclodextdn suggest that an association of only two stilbene chromophores is required to form the "H" aggregate.

A number of surfactant trans-stilbene derivatives have been synthesized and investigated in supported Langmuir-Blodgett assemblies. Layers of pure stilbene surfactants or mixtures with fatty acids show "H" aggregate characteristics including relatively low oscillator strengths for the lowest excited singlet state. Consequently these exhibit relatively low ability, individually, to donate excitation energy or transfer electrons over long ranges.Mixtures of these stilbenes, layered together to form mixed films, also show "H" aggregate characteristics but give evidence for delocalization which can effectively span the width of an entire monolayer and result in efficient energy and electron transfer processes over distances spanning several monolayers. The extension to "H" aggregated and dilute (monomer) diphenylbutadiene and diphenyihexatriene layers results in assemblies in which vectorial energy transfer and redox processes can occur. One of the molecules used as an energy transfer and electron transfer quencher is the cobalt (III) complex of 8 1A. Although this molecule undergoes photochemical intramolecularelectron transfer-induced fragmentation in solution and microheterogeneous media, it shows net photostability in the films but serves a highly effective trap.

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