Donor–Acceptor-Substituted Oligo(1,4-phenylene)s

✍ Scribed by Soungkyoo Kim; Annette Oehlhof; Bernhard Beile; Herbert Meier

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: German
• Weight: 205 KB
• Volume: 92
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200800398

✦ Synopsis

Oligo(para-phenylene)s (DAOPPs) 2a -2d (n ¼ 1 -4) with terminal donor -acceptor substitution (D ¼ C 6 H 13 O, A ¼ 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 (chargetransfer band) for short chains (one or two repeat units, n ¼ 1 or 2). The opposite influence of decreasing ICT and increasing conjugation length leads to a bathochromic series (l max (n þ 1) ! l max (n)) with a fast saturation of l max (n). The effective conjugation length n ECL ¼ 4 corresponds to l 1 349 nm. These results are discussed in the context of other oligo(para-phenylene)s (OPPs).