title: One- and two-photon photochemistry and photophysics of poly(arylenevinylene)s containing a biphenyl moiety.
abstract: Photochemical and photophysical properties were investigated for poly(arylenevinylene)s containing a flexible biphenyl "hinge" unit by applying one-photon (OP) and two-photon (TP) excitation to explore excited-state properties. The poly(arylenevinylene)s were poly[(2,5-dihexyloxy-p-phenylenevinylene)-alt-(4,4'-dihexyloxy-3,3'-biphenylenevinylene)] (1), poly[(2,5-dihexyloxy-p-phenylenevinylene)-alt-(2,2'-dihexyloxy-3,3'-biphenylenevinylene)] (2), and poly[(2,5-dihexyloxy-p-phenylenevinylene)-alt-(2,2'-biphenylenevinylene)] (3). Effective emission quantum yields and related photonic properties were evaluated on a realistic per-chromophore basis using effective conjugation lengths based on the Strickler-Berg relationship. Intramolecular photocyclization was deduced to occur in the one case where the biphenyl molecular connectivity permitted the reaction, based on matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF), heteronuclear multiple-quantum coherence (HMQC)-NMR, and gel-permeation chromatography (GPC) results. The various photoprocesses could be induced by either OP or TP excitation, though the first excited singlet state is the photoactive state. The higher excitation energy of the TP excited state favors indirect population of the S, state by electronic coupling between the TP and OP excited states [lambda(max)TPE (nm): 726; delta (GM): 1=229, 2=215, 3= 109). Photochemical processes occurring from the lowest OP excited state (S1) could therefore also be indirectly induced by TP excitation.
authors.affiliation: University of Potsdam, Institute of Chemistry, Interdisciplinary Research Center for Biopolymers, Karl Liebknecht Str. 24/25 14476 Potsdam-Golm, Germany. vstrehme@rz.uni-postdam.de
authors.forename: Veronika
authors.initials: V
authors.lastname: Strehmel
authors.forename: Ananda M
authors.initials: AM
authors.lastname: Sarker
authors.forename: M Paul M
authors.initials: MP
authors.lastname: Lahti
authors.forename: Frank E
authors.initials: FE
authors.lastname: Karasz
authors.forename: Matthias
authors.initials: M
authors.lastname: Heydenreich
authors.forename: Hendrik
authors.initials: H
authors.lastname: Wetzel
authors.forename: Sophie
authors.initials: S
authors.lastname: Haebel
authors.forename: Strehmel
authors.initials: S
authors.lastname: Bernd