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Controlled regioregularity in oligo(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylenes
1Department of Chemistry and Biochemistry and the Materials Technology Center, Southern Illinois University , Carbondale, Illinois 62901, United States.
Abstract:
A series of three pentameric derivatives of 2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylenes (2-4), with varying degrees of side chain regioregularity, was prepared. The oligomerization chemistry was carried out using repetitive Horner-Wadsworth-Emmons (HWE) reactions of precisely substituted aryl rings with four different substituents. The resulting oligomers were characterized by nuclear magnetic resonance spectroscopy (NMR), cyclic voltammetry (CV) and absorption spectroscopy in solution and in thin films. Each of the oligomers gave discrete (1)H and (13)C NMR spectra. The regioregular pentamer (2) displayed the most resolution between signals and suggests those nuclei reside in more unique chemical environments than the regiorandom pentamers (3 and 4). The solution phase electronic (CV) and absorption properties of each of the new oligomers were found to be essentially identical. In contrast, the thin film absorption spectra were not equivalent. The more regioregular pentamers (2 and 3) possessed a new, red-shifted shoulder structure that suggests the packing order is heavily influenced by side chain regioregularity even at the pentamer level.
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