Monoisomeric Phthalocyanines and Phthalocyanine-Fullerene Dyads with Polar Side Chains: Synthesis, Modeling, and Photovoltage

Synthesis, characterization, molecular modeling, and photovoltage responses of four phthalocyanine-fullerene (Pc-C-60) dyads with two polar (-OH) side chains are described. The synthesized dyads have polar tails either on the Pc (electron donor D) side or on the fullerene (electron acceptor A) side of the dyad, providing a possibility to produce oriented donor-acceptor (D-A) monolayers with revised electron transfer direction when deposited on an aqueous subphase or on a solid surface. In the dyads, phthalocyanine and fullerene have different mutual orientations: in the trans-dyads they have face-to-face orientation, while in the cis-dyads the orientation is face-to-edge. Molecular modeling was used to examine and confirm the spatial arrangements of the synthesized dyads. The Pc-C-60 dyads were deposited successfully onto solid substrates as highly oriented monolayers using the Langmuir-Schafer method. Formation of a vertically oriented monolayer and the following electron transfer from the photoexcited phthalocyanine to fullerene was demonstrated for all dyad monolayers by the time-resolved Maxwell displacement charge method. The electron transfer direction was reversed for the dyads with reversed polarity, demonstrating the ability to control charge transfer direction in the film.