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Issue 38, 2011
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Spectral and intramolecular charge transfer properties in terminal donor/acceptor-substituted all-trans-α,ω-diphenylpolyenes and α,ω-diphenylpolyynes

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Abstract

The absorption spectra and intramolecular charge transfer (CT) properties of terminal donor/acceptor-substituted all-trans-α,ω-diphenylpolyenes (DPE) and α,ω-diphenylpolyynes (DPY) molecules with different conjugated bridge length and substitution modes were investigated by using quantum chemical calculations. We calculated the ground state structures and energy of two series of terminal donor/acceptor DPE and DPY by DFT method. The dependence of conjugation length and substitution modes of the electronic absorption spectra was obtained by TDDFT calculation. The hybrid-GGA XC-functional PBE0 employed in this work was selected from several functionals by comparing the calculated electronic spectral data with experimental value. The CIS-based generalized Mulliken-Hush (GMH) approach was further used to calculate coupling values HAD of the CT process. The calculation shows that both the HOMO–LUMO energy gaps and average bond length alternations between unsaturated multiple (C[triple bond, length as m-dash]C and C[double bond, length as m-dash]C) and saturated single bonds (C–C) decrease regularly with the extension of conjugation. The effective conjugated length (ECL) of DPE and DPY with the same order MM > MP/PM > PP is found together with the regular red shift of the electronic absorption spectra with the extension of conjugation, resulting from the different π-electron delocalization and conjugation efficiency. The GMH analysis further suggests that the CT process in both DPE and DPY is predominated by the through-bond mechanism. The remarkable difference of the conjugated length dependence of squared CT coupling between substituted DPE and DPY is the result of the energetic matching degree of the frontier molecular orbitals between donor/acceptor and the conjugated bridge.

Graphical abstract: Spectral and intramolecular charge transfer properties in terminal donor/acceptor-substituted all-trans-α,ω-diphenylpolyenes and α,ω-diphenylpolyynes

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The article was received on 04 Apr 2011, accepted on 12 Aug 2011 and first published on 30 Aug 2011


Article type: Paper
DOI: 10.1039/C1CP21036J
Citation: Phys. Chem. Chem. Phys., 2011,13, 17273-17283

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    Spectral and intramolecular charge transfer properties in terminal donor/acceptor-substituted all-trans-α,ω-diphenylpolyenes and α,ω-diphenylpolyynes

    X. Ma, L. Yan, X. Wang, Q. Guo and A. Xia, Phys. Chem. Chem. Phys., 2011, 13, 17273
    DOI: 10.1039/C1CP21036J

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