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THE CONFORMATION OF 2,2’-DITHIOPHENE IN NEMATIC SOLVENTS DETERMINED BY H-1-NMR

TitleTHE CONFORMATION OF 2,2’-DITHIOPHENE IN NEMATIC SOLVENTS DETERMINED BY H-1-NMR
Publication TypeJournal Article
Year of Publication1991
AuthorsBeek, LC ter, Zimmerman, DS, Burnell, EE
JournalMolecular Physics
Volume74
Pagination1027-1035
Date PublishedDec
Type of ArticleArticle
ISBN Number0026-8976
Keywords2, 2’-BITHIENYL, BARRIER, LIQUID-CRYSTALS, MOLECULES, orientational order, PHASE, SIZE, SOLUTES
Abstract

In this paper we report a determination of the structure 2,2’-dithiophene dissolved in different nematic liquid crystal solvents. The H-1-NMR spectra of this molecule dissolved in a 55% Merck ZLI 1132/45% N-(4-ethoxybenzylidene)-4’-n-butylaniline (w/w) mixture are recorded at 300 and 304 K and are analysed. The dipolar coupling constants obtained are used to show that the solute molecule exists in both the s-cis and the s-trans conformations. The s-trans conformer is planar and the absolute value of the dihedral angle-PHI between the two thiophene ring planes for the s-cis conformer is found to be (24 +/- 1)degrees. Using the same method of analysis we reinterpreted two additional independent sets of published dipolar coupling constants from H-1-NMR spectra of 2,2’-dithiophene dissolved in Merck Phase IV at room temperature and in 80% N-(4-ethoxybenzylidene)-4’-n-butylaniline/20% O-carbobutoxy-4-oxybenzoic acid ethoxy phenyl ester at 301 K. These additional studies yield the same results for the structure of 2,2’-dithiophene. We also estimate that in each of the three nematic solvents (61 +/- 3)% of the solute 2,2’-dithiophene exists in the s-trans state.

URL<Go to ISI>://A1991GY08500007