Structural and Thermodynamic Characterization of Polyphenylbenzenes

Abstract

The thermodynamic and structural study of a series of polyphenylbenzenes, from benzene, n(Ph) = 0, to hexaphenylbenzene, n(Ph) = 6, is presented. The available literature data for this group of compounds was extended by the determination of the relevant thermodynamic properties for 1,2,4-triphenylbenzene, 1,2,4,5-tetraphenylbenzene, and hexaphenylbenzene, as well as structural determination by X-ray crystallography for some of the studied compounds. Gas phase energetics in this class of compounds was analyzed from the derived standard molar enthalpies of formation in the gaseous phase. The torsional profiles relative to the phenyl-phenyl hindered rotations in some selected polyphenylbenzenes, as well as the gas phase structures and energetics, were derived from quantum chemical calculations. In the ideal gas phase, a significant enthalpic destabilization was observed in hexaphenylbenzene relative to the other polyphenylbenzenes, due to steric crowding between the six phenyl substituents. A relatively low enthalpy of sublimation was observed for hexaphenylbenzene, in agreement with the decreased surface area able to establish intermolecular interactions. The apparently anomalous low entropy of sublimation observed for hexaphenylbenzene is explained by its high molecular symmetry and the six highly hindered phenyl internal rotations. For the series of polyphenylbenzenes considered, it was shown that the differentiation in the entropy of sublimation can be chiefly ascribed to the torsional freedom of the phenyl substituents in the gas phase and the entropy terms related with molecular symmetry.

Energetic and Structural Insights into the Molecular and Supramolecular Properties of Rubrene

“…However, the influence of molecular symmetry on ▵ (Ph) must also be considered. More symmetry leads to lower by an amount of R ⋅ln(σ sym ), where σ sym is the external molecular symmetry number ,. For naphthalene, tetracene and rubrene σ sym =4 ( D 2h point group), and for 1,4‐diphenylnaphthalene and 1,8‐diphenylnaphthalene σ sym =2 ( C 2 point group).…”

Effect of Confined Hindrance in Polyphenylbenzenes

“…Polyphenylbenzenes and their derivatives are polyaromatic compounds with interesting thermal, electronic, and optical properties. − These compounds have several technological applications in the fields of organic semiconductors (OSCs), catalysis, thermal fluids, and biochemistry. − In these compounds, van der Waals dispersion forces are the main component of inter- and intramolecular interactions; thus, they are very important for defining the preferred molecular and supramolecular structures and energetic stability. A previous study demonstrated how phenyl substituents distributed around the central benzene ring can induce some interesting structural changes at the supramolecular and molecular levels . The results have shown that the cohesive energy in the crystal phase is reduced by ortho -bounded phenyl groups which compromise the intermolecular interactions; a situation that is particularly evident in the extreme case of hexaphenylbenzene ( n = 6).…”

Labelling and Comparison of Isomeric Tree-Like Polyphenyl Systems

“…These compounds have been known to be useful in the area of material science and polymer chemistry, which include organic light emitting diodes, catalysts, and transmitters, along with some biological applications [15].…”