title: Blending through-space and through-bond π-π-coupling in [2,2']-paracyclophane-oligophenylenevinylene molecular wires.
abstract: A series of ZnP-pCp-oPPV-C60 conjugates covalently connected through [2,2']-paracyclophane-oligophenylenevinylene (pCp-oPPV) bridges containing one, two, and three [2,2']-paracyclophanes (pCps) has been prepared in multistep synthetic procedures involving Horner-Wadsworth-Emmons olefination reactions and/or Heck type Pd-catalyzed reactions. Molecular modeling suggests that charge transfer is effectively mediated by the pCp-oPPVs through a predominant hole-transfer mechanism. Photophysical investigation supports molecular modeling and reveals two major trends. On one hand, C60 excitation of 1, 2, and 3 leads exclusively to charge transfer between pCp and C60 to afford a ZnP-(pCp-oPPV)(•+)-C60(•-) radical ion pair state without giving rise to a subsequent charge shift to yield the ZnP(•+)-pCp-oPPV-C60(•-) radical ion pair state. On the other hand, ZnP excitation of 1, 2, and 3 results in a rather slow charge transfer between ZnP and C60, after which the ZnP(•+)-pCp-oPPV-C60(•-) radical ion pair state evolves. In temperature-dependent ZnP fluorescence experiments, which were performed in the temperature range from 273 to 338 K, two domains are discernible: low and high temperature behaviors. In the low temperature range (i.e., below 30 °C) the rate constants do not change, suggesting that a superexchange mechanism is the modus operandi. In the high temperature range (i.e., >30 °C) the rate constants increase. Moreover, we find rather strong distance dependence for 1 and 2 and weak distance dependence for 2 and 3. A damping factor of 0.145 Å(-1) is derived for the former pair and 0.012 Å(-1) for the latter.
authors.affiliation: Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany.
authors.forename: Mateusz
authors.initials: M
authors.lastname: Wielopolski
authors.forename: Agustín
authors.initials: A
authors.lastname: Molina-Ontoria
authors.forename: Christina
authors.initials: C
authors.lastname: Schubert
authors.forename: Johannes T
authors.initials: JT
authors.lastname: Margraf
authors.forename: Evangelos
authors.initials: E
authors.lastname: Krokos
authors.forename: Johannes
authors.initials: J
authors.lastname: Kirschner
authors.forename: Andreas
authors.initials: A
authors.lastname: Gouloumis
authors.forename: Timothy
authors.initials: T
authors.lastname: Clark
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Guldi
authors.forename: Nazario
authors.initials: N
authors.lastname: Martín
mesh_terms: D037741:Fullerenes / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011083:Polycyclic Compounds / Q000737:chemistry*; D011145:Polyvinyls / Q000737:chemistry*; D011789:Quantum Theory; D015032:Zinc / Q000737:chemistry*
chemical_list: D037741:Fullerenes; D009942:Organometallic Compounds; D011083:Polycyclic Compounds; D011145:Polyvinyls; C470024:poly(4-phenylenevinylene); C515344:(2.2)paracyclophane; D015032:Zinc; C069837:fullerene C60