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- Title
Poly(triacetylene) Oligomers: Conformational Analysis by X-Ray Crystallography and Synthesis of a 17.8-nm-Long Monodisperse 24-mer.
- Authors
Edelmann, Michael J.; Estermann, Michael A.; Gramlich, Volker; Diederich, François
- Abstract
Starting from the octameric poly(triacetylene) (PTA) oligomer 1e as a large `macromonomer', the monodisperse tetracosamer (24-mer) 1h was prepared by a previously introduced statistical deprotection-oligomerization sequence ( Scheme). It is the longest known molecular rod featuring a fully conjugated, non-aromatic all-carbon backbone. Matrix-assisted laser-desorption-ionization time-of-flight (MALDI-TOF) mass spectrometry was particularly useful in the characterization of oligomer 1h and clearly demonstrated its monodispersity ( Fig. 1). In an effort to further clarify the conformational preferences of PTA oligomers, the X-ray crystal structure of the 3.2-nm-long tetramer 1c was solved ( Figs. 2 - 4). In the solid state, the C=C bonds in 1c all adopt the s- trans conformation with respect to the buta-1,3-diynediyl moieties. The π-conjugated system is perfectly planar, with the squared sum of the deviations of the backbone C-atoms from the best plane amounting to 0.077 Å2. Analysis of the crystal lattice revealed a layered structure, in which the π-conjugated backbone of one oligomer is insulated by the trialkylsilyl groups of adjacent oligomers in neighboring layers.
- Publication
Helvetica Chimica Acta, 2001, Vol 84, Issue 2, p473
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/1522-2675(20010228)84:2<473::AID-HLCA473>3.0.CO;2-8