Synthesis and Structural Characterization of Some New Porphyrin-Fullerene Dyads and Their Application in Photoinduced H2 Evolution

The [3 + 2] cycloaddition reaction of C60 with ethyl isonicotinoylacetate in the presence of piperidine in PhCl at room temperature or in the presence of Mn(OAc)3 in refluxing PhCl gave the pyridyl-containing dihydrofuran-fused C60 derivative (4-C5H4N)C(O)C(C60)CO2Et (1), whereas the phenyl-containing C60 derivative PhC(O)C(C60)CO2Et (2) was similarly prepared by [3 + 2] cycloaddition reaction of C60 with ethyl benzoylacetate in the presence of piperidine or Mn(OAc)3. More interestingly, one of the new porphyrin-fullerene dyads, i.e., [4-C5H4NC(O)C(C60)CO2Et]·ZnTPPH (3, ZnTPPH = tetraphenylporphyrinozinc), could be prepared by coordination reaction of the pyridyl-containing C60 derivative 1 with equimolar ZnTPPH in CS2/hexane at room temperature. In addition, the β-keto ester-substituted porphyrin derivative H2TPPC(O)CH2CO2Et (4) was prepared by a sequential reaction of HO2CCH2CO2Et with n-BuLi in 1:2 molar ratio followed by treatment with H2TPPC(O)Cl in the presence of Et3N and then hydrolysis with diluted HCl, whereas the porphyrinozinc derivative ZnTPPC(O)CH2CO2Et (5) could be prepared by coordination reaction of 4 with Zn(OAc)2 in refluxing CHCl3/MeOH. Particularly interesting is that the second new porphyrin-fullerene dyad H2TPPC(O)C(C60)CO2Et (6) could be prepared by [3 + 2] cycloaddition reaction of 4 with C60 in the presence of piperidine in PhCl at room temperature. In addition, treatment of 6 with Zn(OAc)2 in refluxing CHCl3/MeOH afforded the third new dyad ZnTPPC(O)C(C60)CO2Et (7). All the new compounds 1–7 were characterized by elemental analysis and various spectroscopic methods and particularly for 2, 3, and 5 by X-ray crystallography. The five-component system consisting of an electron donor EDTA, dyad 3, an electron mediator methylviologen (MV2+), the catalyst colloidal Pt, and a proton source HOAc was proved to be effective for photoinduced H2 evolution. A possible pathway for such a type of H2 evolution was proposed.