Bo Keun Park

Remarkably efficient photocurrent generation based on a [60]fullerene-triosmium cluster/Zn-porphyrin/boron-dipyrrin triad SAM.

A new artificial photosynthetic triad array, a [60]fullerene-triosmium cluster/zinc-porphyrin/boron-dipyrrin complex (1, Os(3)C(60)/ZnP/Bodipy), has been prepared by decarbonylation of Os(3)(CO)(8)(CN(CH(2))(3)Si(OEt)(3))(mu(3)-eta(2):eta(2):eta(2)-C(60)) (6) with Me(3)NO/MeCN and subsequent reaction with the isocyanide ligand CNZnP/Bodipy (5) containing zinc porphyrin (ZnP) and boron dipyrrin (Bodipy) moieties. Triad 1 has been characterized by various spectroscopic methods (MS, NMR, IR, UV/Vis, photoluminescence, and transient absorption spectroscopy). The electrochemical properties of 1 in chlorobenzene (CB) have been examined by cyclic voltammetry; the general feature of the cyclic voltammogram of 1 is nine reversible one-electron redox couples, that is, the sum of those of 5 and 6. DFT has been applied to study the molecular and electronic structures of 1. On the basis of fluorescence-lifetime measurements and transient absorption spectroscopic data, 1 undergoes an efficient energy transfer from Bodipy to ZnP and a fast electron transfer from ZnP to C(60); the detailed kinetics involved in both events have been elucidated. The SAM of triad 1 (1/ITO; ITO=indium-tin oxide) has been prepared by immersion of an ITO electrode in a CB solution of 1 and diazabicyclo-octane (2:1 equiv), and characterized by UV/Vis absorption spectroscopy, water contact angle, X-ray photoelectron spectroscopy, and cyclic voltammetry. The photoelectrochemical properties of 1/ITO have been investigated by a standard three-electrode system in the presence of an ascorbic acid sacrificial electron donor. The quantum yield of the photoelectrochemical cell has been estimated to be 29 % based on the number of photons absorbed by the chromophores. Our triad 1 is unique when compared to previously reported photoinduced electron-transfer arrays, in that C(60) is linked by pi bonding with little perturbation of the C(60) electron delocalization.

Cyclic voltammetry modeling, geometries, and electronic properties for metallofullerene complexes with μ3‐η2:η2:η2‐C60 bonding mode

Reduction potential (Ered) values have been calculated and compared with available cyclic voltammetry (CV) data for 10 metallofullerene complexes with the μ3‐η2:η2:η2‐C60 (M3C6[C60]) bonding mode. Consideration of bulk solvent effects is essential for the calculation of the Ered values. Scaling factors for the electrostatic terms of the solvation energies have been introduced to fully describe the experimental cyclic voltammograms with a small mean deviation of 0.07 V. Multiple electron reductions induce movement of the metal cluster moieties on the C60 surface, which is accompanied with the changes in some MC[C60] bonds from π‐type to σ‐type mode. However, the changes in M3C60 distances, as well as the geometric changes of M3 and C60, are small for the reductions, which is in harmony with the high chemical and electrochemical stability of the metallofullerenes. Our population analyses reveal that the added electrons are not localized at the C60 moieties, and electron population in the metal clusters is significant, more than 20% (av. 37%), for all the reductions. Furthermore, we demonstrated that the two close one‐electron redox waves in CV diagrams are strongly correlated with significant electron delocalization, about 40–80%, to the metal‐cluster moieties in these metallofullerene complexes.