title: Testing electron transfer within molecular associates built around anionic C60 and C70 dendrofullerenes and a cationic zinc porphyrin.
abstract: Mono- and bis-functionalized C(60) and C(70) fullerene derivatives (DF, 1-10) that carry one or two oligoanionic dendritic termini in their malonate addends and an oligocationic octapyridinium zinc porphyrin salt (ZnP) were found to self-assemble in buffered aqueous solution to yield a novel series of 1:1 and/or 1:2 electron transfer hybrid associates. Remarkably high association constants-typically on the order of 10(8) M(-1)-were derived that corroborate stable complex formations. A combination of electrostatic and charge-transfer interactions that are operative between the electron-accepting DF and the electron-donating ZnP is considered to contribute to the uniquely high complex stability. First insight into intracomplex excited state interactions came from steady-state and time-resolved fluorescence quenching experiments that were performed with the molecular ZnP/DF hybrid associates. Excited state quenching processes are, for example, evident in form of a bi-exponential fluorescence decay of ZnP-corresponding to a distribution of associated and non-associated ZnP. Unambiguous evidence for an intracomplex electron transfer quenching, namely, formation of ZnP(.+)/C(60) (.-) and ZnP(.+)/C(70) (.-) radical ion pairs, was gathered in time-resolved transient absorption measurements. Lifetimes of these radical ion-pairs range from nanoseconds to a few microseconds.
authors.affiliation: Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, University of Erlangen-Nuremberg, Egerlandstrasse 3, 91058 Erlangen, Germany.
authors.forename: Ginka H
authors.initials: GH
authors.lastname: Sarova
authors.forename: Uwe
authors.initials: U
authors.lastname: Hartnagel
authors.forename: Domenico
authors.initials: D
authors.lastname: Balbinot
authors.forename: Sevda
authors.initials: S
authors.lastname: Sali
authors.forename: Norbert
authors.initials: N
authors.lastname: Jux
authors.forename: Andreas
authors.initials: A
authors.lastname: Hirsch
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Guldi
mesh_terms: D000838:Anions / Q000737:chemistry; D002264:Carboxylic Acids / Q000138:chemical synthesis / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D050091:Dendrimers / Q000737:chemistry*; D004583:Electrons; D005453:Fluorescence; D037741:Fullerenes / Q000737:chemistry*; D008665:Metalloporphyrins / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D055672:Static Electricity; D013237:Stereoisomerism; D013997:Time Factors; D015032:Zinc / Q000737:chemistry*
chemical_list: D000838:Anions; D002264:Carboxylic Acids; D002412:Cations; D050091:Dendrimers; D037741:Fullerenes; D008665:Metalloporphyrins; C069836:fullerene C70; D015032:Zinc; C069837:fullerene C60