Spectroscopic studies of supramolecule formation through cation-induced aggregation of phthalocyanine with four crown ether voids

The alkali cation complexation of phthalocyanine substituted with four crown ether rings (H(2)CRPc) was studied by UV-visible absorption and fluorescence spectroscopy. Cation-induced aggregation of the crowned phthalocyanine occurred in solution. When the diameters of the cations (K+, Rb+) slightly exceeded that of the crown ether ring, they acted cooperatively leading to the formation of a cofacial dimer. Smaller cations (Li+, Na+), which could be encapsulated into the cavity of the crown ether voids, were unable to cause complete conversion to a cofacial dimer. Large Cs+ ions induced sandwich-like aggregation in solution more rapidly. The monomer-dimer equilibrium formation constants for K+-and Rb+-induced aggregation were calculated to be of the order of 10(9) l(2) M(-2).