Abstractmagnified imageOligo(para‐phenylene)s (DAOPPs) 2a–2d (n=1–4) with terminal donor–acceptor substitution (D=C6H13O, A=NO2) were prepared by applying Suzuki cross‐couplings for chain extension and end capping. The push–pull effect induces short‐reaching polarizations of the chain consisting of conjugated but twisted benzene rings, which was studied by NMR measurements. Electron excitation from the ground‐state S0 to the more planar first‐excited singlet state S1 is combined with a strong intramolecular charge transfer (ICT), which is documented by the red shift of the long‐wavelength absorption (charge‐transfer band) for short chains (one or two repeat units, n = 1 or 2). The opposite influence of decreasing ICT and increasing conjugation length leads to a bathochromic series (λmax(n+1)≥λmax(n)) with a fast saturation of λmax (n). The effective conjugation length nECL=4 corresponds to λ∞ 349 nm. These results are discussed in the context of other oligo(para‐phenylene)s (OPPs).
Kaharu, T.; Takahashi, S., Molecular Crystals and Liquid Crystals Science and Technology, Section A: Molecular Crystals and Liquid Crystals, 1994, vol. 257, p. 35 - 42
作者:Kaharu, T.、Takahashi, S.
DOI:——
日期:——
Relationship between Molecular Association and Re-entrant Phenomena in Polar Calamitic Liquid Crystals
作者:Richard J. Mandle、Stephen J. Cowling、Ian Sage、M. Eamon Colclough、John W. Goodby
DOI:10.1021/jp512093j
日期:2015.2.19
conjectured that the degree of association for the nitro systems is greater than that for the cyano analogues. This hypothesis was tested by using measured dielectric anisotropies and computed molecular properties to obtain a value of the Kirkwood factor, g, which describes the degree of association of dipoles in a liquid. These computed values of g confirm that the degree of association for nitro materials is