Peripheral Stepwise Degradation of a Porphyrin J-Aggregate

Abstract

For metalation of the acidic form of tetrakis(4-sulfonatophenyl)porphyrin (dianionic H(4)TPPS(4)) by Cu(II), the order of reagent mixing determines the rate and mechanism of CuTPPS(4) formation. When copper salts are added last, the kinetic profile is fit as a (pseudo)-first-order process. However, J-aggregates of the H(4)TPPS(4) porphyrin are rapidly formed at pH ~ 3 when Cu(II) salts are incorporated in solution prior to porphyrin addition. The subsequent porphyrin units metalation leads to the disassembling of these arrays via a pseudo-zero-order kinetic profile, suggesting an attack of the metal ion at the rims of the nanostructure.