title: Supramolecular triad and pentad composed of zinc-porphyrin(s), oxoporphyrinogen, and fullerene(s): design and electron-transfer studies.
abstract: By adopting a "covalent-coordinate" bonding approach, novel supramolecular pentad and triad molecules composed of zinc-porphyrin(s), fullerene(s), and oxoporphyrinogen redox-/photoactive entities have been constructed, and also characterized by means of spectral and electrochemical techniques. The geometry and electronic structures of the pentad and the triad were deduced by means of DFT calculations. Free-energy calculations suggested that the photoinduced electron/energy transfer from the zinc-porphyrin (ZnP) singlet-excited state to the imidazole modified fullerene (ImC(60)) acceptor and oxoporphyrinogen (OxP) entities is feasible for both the triad and the pentad. The charge-separation rates (k(CS)) determined from picosecond time-resolved emission studies were higher for pentad (C(60)Im:ZnP)(2)-OxP than for the corresponding triad, C(60)Im:ZnP-OxP. A comparison of the k(CS) values previously reported for the covalently linked bis(zinc-porphyrin)-oxoporphyrinogen triad suggests that employing a fullerene acceptor improves the electron-transfer rates. Nanosecond transient absorption studies provide evidence for the occurrence of electron-transfer processes. Lifetimes of the radical ion pairs (tau(RIP)) are in the range of hundreds of nanoseconds, which indicates that there is charge stabilization in the supramolecular systems.
authors: Department of Chemistry, Wichita State University, 1845 Fairmount, Wichita, KS 67260-0051, USA.
authors: Amy Lea
authors: AL
authors: Schumacher
authors: Atula S D
authors: AS
authors: Sandanayaka
authors: Jonathan P
authors: JP
authors: Hill
authors: Katsuhiko
authors: K
authors: Ariga
authors: Paul A
authors: PA
authors: Karr
authors: Yasuyuki
authors: Y
authors: Araki
authors: Osamu
authors: O
authors: Ito
authors: Francis
authors: F
authors: D'Souza
mesh_terms: D004563:Electrochemistry; D004583:Electrons; D037741:Fullerenes / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods; D008956:Models, Chemical; D015394:Molecular Structure; D010777:Photochemistry; D011165:Porphyrinogens / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013997:Time Factors; D015032:Zinc / Q000737:chemistry*
chemical_list: D037741:Fullerenes; D046911:Macromolecular Substances; D011165:Porphyrinogens; D011166:Porphyrins; D015032:Zinc