title: Delocalization of Coherent Triplet Excitons in Linear Rigid Rod Conjugated Oligomers.
abstract: In this work, the triplet state delocalization in a series of monodisperse oligo(p-phenyleneethynylene)s (OPEs) is studied by pulsed electron paramagnetic resonance (EPR) and pulsed electron nuclear double resonance (ENDOR) determining zero-field splitting, optical spin polarization, and proton hyperfine couplings. Neither the zero-field splitting parameters nor the optical spin polarization change significantly with OPE chain length, in contrast to the hyperfine coupling constants, which showed a systematic decrease with chain length n according to a 2/(1 + n) decay law. The results provide striking evidence for the Frenkel-type nature of the triplet excitons exhibiting full coherent delocalization in the OPEs under investigation with up to five OPE repeat units and with a spin density distribution described by a nodeless particle in the box wave function. The same model is successfully applied to recently published data on π-conjugated porphyrin oligomers.
authors.affiliation: Fachbereich Chemie, Universität Konstanz , 78457 Konstanz, Germany.
authors.forename: Christian
authors.identifier: http://orcid.org/0000-0002-8813-9001
authors.initials: C
authors.lastname: Hintze
authors.affiliation: Fachbereich Chemie, Universität Konstanz , 78457 Konstanz, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Korf
authors.affiliation: Fachbereich Chemie, Universität Konstanz , 78457 Konstanz, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Degen
authors.affiliation: Fachbereich Chemie, Universität Konstanz , 78457 Konstanz, Germany.
authors.forename: Friederike
authors.initials: F
authors.lastname: Schütze
authors.affiliation: Fachbereich Chemie, Universität Konstanz , 78457 Konstanz, Germany.
authors.forename: Stefan
authors.identifier: http://orcid.org/0000-0002-6618-6659
authors.initials: S
authors.lastname: Mecking
authors.affiliation: Fachbereich Chemie, Universität Konstanz , 78457 Konstanz, Germany.
authors.forename: Ulrich E
authors.initials: UE
authors.lastname: Steiner
authors.affiliation: Fachbereich Chemie, Universität Konstanz , 78457 Konstanz, Germany.
authors.forename: Malte
authors.identifier: http://orcid.org/0000-0002-3571-3452
authors.initials: M
authors.lastname: Drescher