A study of the conformation of some 3,3′-bithienyl and biselenienyl derivatives by measurements of twisting powers in nematic liquid crystals and of dipole moments |
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Authors: | Caterina Arnone Giovanni Gottarelli Gian Piero Spada Domenico Spinelli Otto Exner |
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Affiliation: | Istituto di Scienze Chimiche, Università di Bologna, Via S. Donato 15, 40127 Bologna Italy Czechoslovak Academy of Sciences, Institute of Organic Chemistry and Biochemistry, 166 10 Praha Czechoslovakia |
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Abstract: | The conformation of chiral 2,2′-dinitro-3,3′-bithienyl-4,4′-dicarboxylic acid (Ia), its dimethylester (Ib), and analogous selenium derivatives Ic and Id was investigated by means of induced cholesteric mesophases. A parallel investigation on the diester (Ib) and on other model 3,3′-bithienyls was carried out with dipole moment measurements. The conclusions reached with the two independent methods for derivative Ib are in excellent agreement and indicate, if a single conformation is assumed, a preferred cisoid conformation with a dihedral angle somewhat smaller than 90°. Alternatively, if the existence of both cisoid and transoid conformations having supplementary dihedral angles is assumed, the data indicate a higher population for the cisoid form. |
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