The Influence of the Vinyl Terminal Group on the Poly(Para-Phenylenevinylene) Charge Transfer Integrals

Abstract

The charge transport properties of organic semiconductors are one of the foremost limiting factors in technological applications of these materials, which are becoming important competitors with respect to the inorganic semiconductors. In fact, conjugated organic molecules are used at present as active materials in different types of devices. For this reason, the theoretical study of the electron and hole mobility, carried out in order to give hints for the design of new molecules or for the optimization of their supramolecular organization, is a task of great interest. Here, we present the results of a quantum chemical study, in the framework of the Marcus and density functional theories, on the effects of terminal groups (when they directly interact with the pi-conjugated system of the organic semiconductors) on the charge carriers mobility of organic semiconductors. In particular, using a representative oligomer of poly(para-phenylenevinylene) as a model system, we have found that strong effects on the predicted values of the intramolecular transfer integrals as well as on their dependence on the supramolecular organizations occur, when the vinyl moiety (as ending group) is taken into account.

Computational Analysis of Electron Transfer Kinetics for CO2 Reduction with Organic Photoredox Catalysts

“…While electron-donating groups lower the diabatic couplings relative to H-substituted OPP, electron-withdrawing groups lead to small enhancements in J (Table S3, Supporting Information). Although J is known to be a strong function of interfragment separation, ,, combined changes in substituents and interfragment separations make it difficult to isolate the role played by σ p in determining J . If this reaction were in the nonadiabatic regime, smaller couplings for electron-donating groups could lead to decreased rates, but the magnitudes of J observed in our work indicate that couplings are not altering ET rate coefficients.…”

“…Oligo­( p -phenylenes) (OPPs) were first proposed as promising candidates for photoredox reduction of CO 2 in 1992 by Matsuoka and co-workers . More recently, studies demonstrated amino acid synthesis and styrene hydrocarboxylation from CO 2 using OPPs. , Owing to their potential applications in areas besides catalysis including photoactive materials such as organic light-emitting diodes, the excited state properties of OPPs are well-characterized. − Several studies also probe the sensitivity of OPP excitations to torsional changes, chain length, and isomeric forms. ,, However, fundamental computational studies of electron transfer (ET) from excited states or quenched radicals are largely restricted to intramolecular processes for semiconductor applications. , This work therefore aims to determine driving forces for ET from OPP to CO 2 and utilizes the outcomes to identify structural modifications necessary for achieving rate enhancements.…”

Theoretical studies of molecular orientation and charge recombination in poly-paraphenylenevinylene light-emitting diodes

“…14,20,21 Upon rotational orientation, the donor or acceptor of the dimer is rotated around the principal axis of inertia (the x-axis in Fig. 2).…”

“…The molecular center-to-center distance in the face-to-face dimer is set to be 4.0 Å, similar to that reported in previous studies. 14,20,21 Upon rotational orientation, the donor or acceptor of the dimer is rotated around the principal axis of inertia (the x-axis in Fig. 2).…”

“…12,13 These p-stacked structures have a large transfer integral; this parameter represents the probability of adiabatic electron transfer (ET) in the conjugated material. 2,6,8,14 On the other hand, the mobilities in the crystalline derivative of tetrathiafulvalene increase in the order of partial stacking, lamella (stacking), and the herringbone structure. 15 Similarly, the herringbone structures of rubrene and tetracene exhibit very high mobilities of 24.5 and 5 cm 2 V À1 s À1 , respectively.…”