TY - JOUR
T1 - Dinitro and quinodimethane derivatives of terthiophene that can be both oxidized and reduced. Crystal structures, spectra, and a method for analyzing quinoid contributions to structure
AU - Pappenfus, Ted M.
AU - Raff, Jonathan D.
AU - Hukkanen, Eric J.
AU - Burney, Jason R.
AU - Casado, Juan
AU - Drew, Steven M.
AU - Miller, Larry L.
AU - Mann, Kent R.
PY - 2002/8/23
Y1 - 2002/8/23
N2 - Two new oligothiophenes, the dinitro compound 3′,4′-dibutyl-5,5″- dinitro-2,2′:5′,2″-terthiophene (1) and the quinodimethane 3′,4′-dibutyl- 5,5″-bis(dicyanomethylene)-5,5″-dihydro- 2,2′:5′,2″-terthiophene (2), have been synthesized and studied with electrochemistry, UV-vis-NIR-IR spectroscopy, ESR, and X-ray crystallography. These compounds, designed to be both electron and hole carriers, show redox properties that are unusual for oligothiophenes. Cyclic voltammetry and spectroelectrochemistry demonstrated that each compound could be oxidized to a cation radical and reduced to an anion radical and dianion. The spectra of 2 and its three redox partners were analyzed in terms of a limiting structure in which the neutral 2 has orbitals corresponding to those of a substituted-terthiophene dication. Compound 1 crystallizes with the thiophene rings held in an unusual nonplanar, cisoid configuration in face-to-face π-stacks, with a spacing between molecules of 3.65 A. The C-C bond lengths of the outer nitro-substituted rings have quinoid character. Compound 2 crystallizes with the thiophene rings in a planar, transoid configuration. The molecules are held in π-stacks formed from π-dimers with a spacing between molecules of 3.47 and 3.63 Å. The C-C bond distances of the thiophene rings of 1 and 2 and other oligomers were analyzed by a principal component analysis. The analysis found that 93% of the structural variance resided in one principal component related to the quinoid structure of the oligothiophene moiety. The analysis reliably demonstrated a quinoid contribution to the structure of 1. This method should be applicable to understanding the structure of other conjugated molecules in which quinoid structures contribute.
AB - Two new oligothiophenes, the dinitro compound 3′,4′-dibutyl-5,5″- dinitro-2,2′:5′,2″-terthiophene (1) and the quinodimethane 3′,4′-dibutyl- 5,5″-bis(dicyanomethylene)-5,5″-dihydro- 2,2′:5′,2″-terthiophene (2), have been synthesized and studied with electrochemistry, UV-vis-NIR-IR spectroscopy, ESR, and X-ray crystallography. These compounds, designed to be both electron and hole carriers, show redox properties that are unusual for oligothiophenes. Cyclic voltammetry and spectroelectrochemistry demonstrated that each compound could be oxidized to a cation radical and reduced to an anion radical and dianion. The spectra of 2 and its three redox partners were analyzed in terms of a limiting structure in which the neutral 2 has orbitals corresponding to those of a substituted-terthiophene dication. Compound 1 crystallizes with the thiophene rings held in an unusual nonplanar, cisoid configuration in face-to-face π-stacks, with a spacing between molecules of 3.65 A. The C-C bond lengths of the outer nitro-substituted rings have quinoid character. Compound 2 crystallizes with the thiophene rings in a planar, transoid configuration. The molecules are held in π-stacks formed from π-dimers with a spacing between molecules of 3.47 and 3.63 Å. The C-C bond distances of the thiophene rings of 1 and 2 and other oligomers were analyzed by a principal component analysis. The analysis found that 93% of the structural variance resided in one principal component related to the quinoid structure of the oligothiophene moiety. The analysis reliably demonstrated a quinoid contribution to the structure of 1. This method should be applicable to understanding the structure of other conjugated molecules in which quinoid structures contribute.
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U2 - 10.1021/jo025572b
DO - 10.1021/jo025572b
M3 - Article
C2 - 12182637
AN - SCOPUS:0037162864
SN - 0022-3263
VL - 67
SP - 6015
EP - 6024
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
IS - 17
ER -