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Donor–Acceptor‐Substituted Oligo(1,4‐phenylene)s
Author(s) -
Kim Soungkyoo,
Oehlhof Annette,
Beile Bernhard,
Meier Herbert
Publication year - 2009
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200800398
Subject(s) - chemistry , bathochromic shift , phenylene , acceptor , intramolecular force , excited state , crystallography , photochemistry , singlet state , ground state , photoexcitation , stereochemistry , fluorescence , atomic physics , polymer , condensed matter physics , physics , organic chemistry , quantum mechanics
Oligo( para ‐phenylene)s (DAOPPs) 2a – 2d ( n =1–4) with terminal donor–acceptor substitution (D=C 6 H 13 O, A=NO 2 ) 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 S 0 to the more planar first‐excited singlet state S 1 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 ( λ max ( n +1)≥ λ max ( n )) with a fast saturation of λ max ( n ). The effective conjugation length n ECL =4 corresponds to λ ∞ 349 nm. These results are discussed in the context of other oligo( para ‐phenylene)s (OPPs).