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Efficient intramolecular charge transfer in oligoyne-linked donor–π–acceptor molecules.

Pålsson, L.-O. and Wang, C. and Batsanov, A.S. and King, S.M. and Beeby, A. and Monkman, A.P. and Bryce, M.R. (2009) 'Efficient intramolecular charge transfer in oligoyne-linked donor–π–acceptor molecules.', Chemistry - a European journal., 16 (5). pp. 1470-1479.

Abstract

Studies are reported on a series of triphenylamine–(C[TRIPLE BOND]C)n–2,5-diphenyl-1,3,4-oxadiazole dyad molecules (n=1–4, 1, 2, 3 and 4, respectively) and the related triphenylamine-C6H4–(C[TRIPLE BOND]C)3–oxadiazole dyad 5. The oligoyne-linked D–π–A (D=electron donor, A=electron acceptor) dyad systems have been synthesised by palladium-catalysed cross-coupling of terminal alkynyl and butadiynyl synthons with the corresponding bromoalkynyl moieties. Cyclic voltammetric studies reveal a reduction in the HOMO–LUMO gap in the series of compounds 1–4 as the oligoyne chain length increases, which is consistent with extended conjugation through the elongated bridges. Photophysical studies provide new insights into conjugative effects in oligoyne molecular wires. In non-polar solvents the emission from these dyad systems has two different origins: a locally excited (LE) state, which is responsible for a π*[RIGHTWARDS ARROW]π fluorescence, and an intramolecular charge transfer (ICT) state, which produces charge-transfer emission. In polar solvents the LE state emission vanishes and only ICT emission is observed. This emission displays strong solvatochromism and analysis according to the Lippert–Mataga–Oshika formalism shows significant ICT for all the luminescent compounds with high efficiency even for the longer more conjugated systems. The excited-state properties of the dyads in non-polar solvents vary with the extent of conjugation. For more conjugated systems a fast non-radiative route dominates the excited-state decay and follows the Engelman–Jortner energy gap law. The data suggest that the non-radiative decay is driven by the weak coupling limit.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1002/chem.200902099
Publisher statement:This is the peer reviewed version of the following article: Pålsson, L.-O., Wang, C., Batsanov, A.S., King, S.M., Beeby, A., Monkman, A.P. & Bryce, M.R. (2010). Efficient Intramolecular Charge Transfer in Oligoyne-Linked Donor–π–Acceptor Molecules. Chemistry - A European Journal 16(5): 1470-1479, which has been published in final form at https://doi.org/10.1002/chem.200902099. This article may be used for non-commercial purposes in accordance With Wiley-VCH Terms and Conditions for self-archiving.
Date accepted:28 July 2009
Date deposited:07 September 2017
Date of first online publication:18 December 2009
Date first made open access:No date available

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