A non-covalent supramolecular complex combining porphyrin (Por), phthalocyanine (Pc) and fullerene [ C 60], was obtained through zinc metal-pyridine coordination between a covalently meso-linked heterodimer ZnPor-ZnPc (4) and a N-pyridylfulleropyrrolidine derivative (5). The complexation was studied in toluene by absorption and fluorescence binding studies, and evidenced that the coordination of the N-pyridylfulleropyrrolidine (5) occurs preferentially through the zinc ion center of ZnPc (log K > 6.0) rather than ZnPor (log K = 5.23). Steady-state and time-resolved spectroscopies evidenced that upon selective excitation of either the Por, or the Pc moiety in [( ZnPor-ZnPc )∪ C 60], the singlet excited state of Pc was generated efficiently in both cases (either from singlet-singlet energy transfer from 1Por* to Pc, or directly after selective excitation of the Pc moiety). Next, an electron transfer occurred from the 1Pc* to the C 60 to generate the charge-separated specie [( ZnPor-ZnPc •+)∪ C 60•-]. Finally, the back electron transfer afforded the Pc triplet excited state rather than the ground state. The introduction of a covalent meso-linkage between Por and Pc in the heterodimer 4 and in the supramolecular assembly 4∪5 induces appreciable differences toward the photo-induced processes and the binding constants in comparison with other β-covalently linked analogue systems.
Cover Feature: Competitive Energy and Electron Transfer in β-Functionalized Free-Base Porphyrin-Zinc Porphyrin Dimer Axially Coordinated to C60
: Synthesis, Supramolecular Formation and Excited-State Processes (Chem. Eur. J. 52/2017)