Phase transition equilibrium of terthiophene isomers

• Type: Article in International Scientific Journal
• Date: 2011

Authors

Costa, JCS (Author) Other; Carlos F R A C Lima (Author) Other; Marisa A A Rocha (Author) Other; Ligia R Gomes (Author) Other; Luis M N B F Santos (Author) FCUP

Journal

Title: Journal of Chemical Thermodynamics

Vol. 43 No. 2

Pages: 133-139

ISSN: 0021-9614

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 12 Citations

Scopus - 12 Citations

Scientific classification

FOS: Engineering and technology > Mechanical engineering

Other information

Authenticus ID: P-002-VMQ

DOI: 10.1016/j.jct.2010.08.007

Abstract (EN): The thermodynamic study of the phase transition (fusion and sublimation) of 2,2':5',2 ''-terthiophene and 3,2':5',3 ''-terthiophene is presented. The obtained data is used to evaluate the (solid + liquid) and (solid + gas) phase equilibrium, and draw the phase diagrams of the pure compounds near the triple point coordinates. For each compound the vapour pressures at different temperatures were measured by a combined Knudsen effusion method with a vacuum quartz crystal microbalance. Based on the previous results, the standard molar enthalpies, entropies and Gibbs energies of sublimation were derived at T = 298.15 K. For the two terthiophenes and for 3,3'-bithiophene, the temperature, and the molar enthalpies of fusion were measured in a power compensated differential scanning calorimetry. The relationship between structure and energetics is discussed based on the experimental results, ab initio calculations and previous literature data for 2,2'-bithiophene and 3,3'-bithiophene. The 3,2':5',3 ''-terthiophene shows a higher solid phase stability than the 2,2':5',2 ''-terthiophene isomer arising from the higher cohesive energy due to positioning of the sulphur atom in the thiophene ring. The higher phase stability of 3,3'-bithiophene relative to 2,2'-bithiophene isomer is also related to its higher absolute entropy in the solid phase associated with the ring positional degeneracy observed in the crystal structure of this isomer. A significant differentiation in the crystal phase stability between isomers was found.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7