Design, synthesis and study of the bridged and cofacially-arrayed poly-p-phenylene molecular wires

Matthew J Modjewski, Marquette University

Abstract

Two novel series of bridged and cofacially-arrayed poly- p -phenylenes have been designed synthesized and studied. The bridged poly-p -phenylenes have been synthesized from a readily available diacetylenic precursor utilizing three high yielding steps, and their structures were determined by 1 H/13 C NMR spectroscopy as well as X-ray crystallography. The racemization barrier between the two atropoisomers was found to be ∼12 Kcal mol-1 ; the versatility of the synthesis employed was extended to synthesis a triply bridged tetra- p -phenylene and a quadruply bridged penta-p -phenylene. The cofacially-arrayed poly-p -phenylenes have shown that the X-ray crystal structures of the neutral compounds are largely dominated by C-H--π-interactions interactions while the dicationic species display an almost perfect parallel arrangement of the cofacially-arrayed poly- p -phenylene moieties. Electrochemistry of the cofacially-arrayed poly-p -phenylenes and their model compounds consistently met the reversibility criteria. Electronic absorption spectra show that the two series are strikingly similar; however the emission spectra show that the cofacially-arrayed poly-p -phenylenes are significantly broader and bathochromically shifted in comparison to the model compounds. Electrochemical oxidation of 2,3,6,7-tetramethoxy-9,10-dimethylanthra-cene showed that it undergoes a highly reversible electrochemical oxidation ( Eox = 0.81 V vs. SCE) and forms a modestly stable cation-radical salt in solution. The X-ray crystal structure showed the presence of a dicationic homotrimer that decomposes in the spiro adduct when allowed to sit at ambient temperatures.

Subject Area

Organic chemistry

Recommended Citation

Modjewski, Matthew J, "Design, synthesis and study of the bridged and cofacially-arrayed poly-p-phenylene molecular wires" (2009). Dissertations (1962 - 2010) Access via Proquest Digital Dissertations. AAI1467978.
http://epublications.marquette.edu/dissertations/AAI1467978

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