Induction of self-organization between zinc phthalocyanine (ZnPc) and C60 moieties in a novel amphiphilic ZnPc-C60 salt results in uniformly nanostructured 1-D nanotubules. Their photoreactivity, in terms of ultrafast charge separation (i.e., approximately 1012 s-1) and ultraslow charge recombination (i.e., approximately 103 s-1), is remarkable. In addition, the observed ZnPc*+-C60*- lifetime of 1.4 ms implies, relative to that of the monomeric ZnPc-C60 ( approximately 3 ns), an impressive stabilization of 6 orders of magnitude.
A thorough investigation on the physicochemical properties, including electrochemisty and photophysics, of
a new class of donor−acceptor hybrids, namely, phthalocyanine-fullerene dyads, consisting of free base 1a
and zinc and copper complexes 1b and 1c, respectively, brings new insights into the stabilization of charge-separated radical ion pairs and the impact of redoxactive transition-metal centers on the photoperformance of
macrocyclic phthalocyanines. In these dyads, the role of the phthalocyanines is twofold: First, it functions as
an antenna (i.e., absorbing very efficiently light in the visible region of the solar spectrum) and, second, as
a donor moleculeonce photoexcited. The initial photoexcitation is succeeded by an ultrafast electron transfer
largely due to the strong electronic coupling between electron donor (Pc) and electron acceptor (C60) generating
surprisingly long-lived radical ion pairs Pc•+−C60
•- with lifetimes of several nanoseconds. Large driving
forces for the charge recombination and small reorganization energies of the Pc−C60 ensembles corroborate
slow charge recombination dynamics, which, in turn, helps to rationalize the long lifetimes of Pc•+−C60
•-.
Phthalocyanines linked to C60 have been synthesized by two general strategies. One of them involves the addition of an azomethine ylide prepared in situ from a formyl phthalocyanine to C60, and the other one involves a statistical condensation of two substituted phthalonitriles, one of them bearing the C60 moiety covalently attached. These new phthalocyanine-fullerene dyads have been studied by cyclic voltammetry and Osteryoung square wave voltammetry, and inter- and intramolecular electronic interactions between the two electroactive subunits have been demonstrated.
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