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.

Synthesis and Characterization of Water-Soluble Phenylene−Vinylene-Based Singlet Oxygen Sensitizers for Two-Photon Excitation

“…Moreover, distinct isosbestic points in the spectra indicate that, under the conditions of these experiments, only one degradation product is formed in each case. Similar behavior has been observed by Strehmel et al upon irradiation of other OPV systems.

8 UV−vis absorption spectra of two MTEG-substituted sensitizers recorded as a function of elapsed exposure to 400 nm light in aerated H 2 O (CW laser operated at 30 mW, irradiated spot size ∼5 mm in diameter).

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Enhanced Two‐Photon Absorption of Organic Chromophores: Theoretical and Experimental Assessments

“…A large body of experimental data is available for many families of quadrupolar systems. [3,33,36,57,58,63,76,78,81,85,86,[89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][104][105][106][107] Their nonlinear response is a non-trivial function of terminal donor and acceptor strength, π-conjugated bridge length and type, nature of the conjugated core, torsional disorder, symmetry and topology. [58] In this subsection we exemplify some of these relationships using two different families of quadrupoles to derive general trends in terms of TPA cross sections and peak positions.…”

“…Thereby, attention has progressively moved from the well-known push-pull dipolar molecular structures [34,41,[75][76][77][78][79][80][81][82][83][84][85][86][87][88] to quadrupoles [3,33,36,57,58,63,76,78,81,85,86,[89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][104][105][106][107] and, more recently, toward complex molecular architectures. Quadrupoles have been found to be more efficient than dipoles in terms of TPA, in particular for multiphoton-based opticallimiting applications.…”

Distyrylbenzene-based segmented conjugated polymers: Synthesis, thin film morphology and chemosensing of hydrophobic and hydrophilic nitroaromatics in aqueous media

“…In this context, an efficacious concept of macromolecular design aiming to customize the physical and electronic properties of conjugated polymers consists in the regular insertion in the polymer backbone of atomic or molecular motifs which tailor the π-conjugation length. Thus, a variety of regularly segmented conjugated polymers (SCPs) have been synthesized by linking aromatic segments of discrete size with spacers such as biphenylene [8], binaphthylene [9], paracyclophane [10], linear alkylene [11,12] and oxyethylene chains [13], oxygen atoms [14], silicon atoms [15,16] and sp 3 -carbon atoms of the norbornylene [17], fluorenylidene [18] and isopropylidene groups [19][20][21] all of which break conjugation in a controlled manner.…”