Effect of host–guest interactions on the photophysical properties of a monocrown ether substituted phthalocyanine

The photophysical properties of supramolecular systems consisting of a monocrown ether substituted phthalocyanine CRPc (1) and potassium salts of p-nitrobenzoic acid (2), picric acid (3) and porphyrin monocarboxylic acid (4) are described. The fluorescence from CRPc is quenched by complexation with (2), (3) and (4) giving downward curving Stern–Volmer plots. The quenching constants and the fraction of CRPc accessible to quenching are calculated using the modified Stern–Volmer equation. Times-resolved fluorescence measurements for the systems show biexponential decay profiles. The lifetimes for long-lived and short-lived components determined for the each system remain constant. The results show that host–guest complexation not only are important in the supramolecular preorganization of donor–acceptor dyads based on noncovalent interaction but also may directly mediate electron transfer process.