Phenylnaphthalenes: Sublimation Equilibrium, Conjugation, and Aromatic Interactions

• Type: Article in International Scientific Journal
• Date: 2012

Authors

Carlos F R A C Lima (Author) Other; Marisa A A Rocha (Author) Other; Bernd Schroeder (Author) Other; Ligia R Gomes (Author) Other; John N Low (Author) Other; Luis M N B F Santos (Author) FCUP

Journal

Title: Journal of Physical Chemistry B

Vol. 116 No. 6

Pages: 3557-3570

ISSN: 1520-6106

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 24 Citations

Scopus - 24 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-002-C0Q

DOI: 10.1021/jp2111378

Abstract (EN): In this work, the interplay between structure and energetics in some representative phenylnaphthalenes is discussed from an experimental and theoretical perspective. For the compounds studied, the standard molar enthalpies, entropies and Gibbs energies of sublimation, at T = 298.15 K, were determined by the measurement of the vapor pressures as a function of T, using a Knudsen/quartz crystal effusion apparatus. The standard molar enthalpies of formation in the crystalline state were determined by static bomb combustion calorimetry. From these results, the standard molar enthalpies of formation in the gaseous phase were derived and, altogether with computational chemistry at the B3LYP/6-311++G(d,p) and MP2/cc-pVDZ levels of theory, used to deduce the relative molecular stabilities in various phenylnaphthalenes. X-ray crystallographic structures were obtained for some selected compounds in order to provide structural insights, and relate them to energetics. The thermodynamic quantities for sublimation suggest that molecular symmetry and torsional freedom are major factors affecting entropic differentiation in these molecules, and that cohesive forces are significantly influenced by molecular surface area. The global results obtained support the lack of significant conjugation between aromatic moieties in the alpha position of naphthalene but indicate the existence of significant electron delocalization when the aromatic groups are in the beta position. Evidence for the existence of a quasi T-shaped intramolecular aromatic interaction between the two outer phenyl rings in 1,8-di([1,1-biphenyl]4-yl)naphthalene was found, and the enthalpy of this interaction quantified on pure experimental grounds as -(11.9 +/- 4.8) kJ.mol(-1), in excellent agreement with the literature CCSD(T) theoretical results for the benzene dimer.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 14