The Coulomb complex formation of a dendritic fullerene oligocarboxylate (1(8-)) and an octapyridinium zinc porphyrin salt (ZnP8+) was investigated. A Job plot obtained by monitoring the Soret absorption of ZnP8+ upon addition of I in a phosphate buffer (pH 7.2, ionic strength = 0.012) indicated the formation of a 1:1 complex, ZnP8+/1(8-), for which an association constant of (3.5 +/- 1.0) x 10(8) M-1 was determined. Parallel fluorescence titration experiments revealed that the ZnP8+ emission is strongly quenched in the ZnP8+/1(8-)complex. In particular, the noted decrease of fluorescence intensity in ZnP8+ with variation of 1(8-) and evidence for a new short-lived emissive component suggest a static quenching event inside a ZnP8+/1(8-) complex. From the fluorescence titration, a value of (1.1 +/- 0.1) x 10(8) M-1 for the association constant of the ZnP8+/ 1(8-) complex at pH 7.2 was derived. The association constant decreased, however, when the ionic strength of the solution was raised. Electron-transfer quenching was confirmed by transient absorption spectroscopy, which showed the fingerprint absorptions of the ZnP8+ radical cation and the 1(8-) radical anion and a lifetime of 1.1 mus for the charge-separated state. Molecular dynamic simulations offer insight into the supramolecular structure of the fullerene-porphyrin hybrid, ZnP8+/1(8-).