Self-association of oligothiophenes in isotropic systems

• Type: Article in International Scientific Journal
• Date: 2014

Authors

Carlos F R A C Lima (Author) Other; Costa, JCS (Author) FCUP; Tiago L P Galvao (Author) Other; Hilario R Tavares (Author) Other; Artur M S Silva (Author) Other; Luis M N B F Santos (Author) FCUP

Journal

Title: Physical Chemistry Chemical Physics

Vol. 16

Pages: 14761-14770

ISSN: 1463-9076

Publisher: Royal Society of Chemistry

Indexing

ISI Web of Knowledge - 8 Citations

Scopus - 8 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-009-ND1

DOI: 10.1039/c4cp01101e

Abstract (EN): The self-association equilibrium constants, K-ass, for the dimerization of some small oligothiophenes in acetone, acetonitrile and chloroform were measured by H-1 NMR spectroscopy. The gas phase interaction energies for some oligothiophene dimers were determined by computational quantum chemistry. The H-1 NMR results indicate that K-ass generally increases with the chain length (the number of thienyl rings, n) and solvent polarity; however, K-ass for thiophene (n = 1) was found to be higher than for the bithiophenes (n = 2). The linear oligothiophenes 2,2'-bithiophene and 2,2',5',2 ''-terthiophene were found to self-associate less than their corresponding nonlinear isomers 3,30-bithiophene and 3,2',5',3 ''-terthiophene in solution and in the gas phase. For a-quaterthiophene (n = 4) K-ass in solution was found to be smaller than expected. The non-linear dependence of the standard molar Gibbs energy of self-association, Delta(ass)G(m)(0), on the chain length in solution could be nicely reproduced and related to the conformational entropy change of dimerization. It was observed that the melting properties of oligothiophenes correlate well with their tendency to self-associate, with more self-association leading to increased liquid stability, and thus lower melting temperatures. These results highlight the relevance of self-association in isotropic systems for the correct molecular interpretation of phase equilibria.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10