2,6-Diphenylpyridine

Rocha, Marisa A.A.; Low, John N.; Gomes, Lígia R.; Quesada, Alberto; Santos, Luı́s M. N. B. F.

doi:10.1107/s1600536807058850

Cited by 1 publication

(1 citation statement)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The observed orders for the enthalpic and entropic contributions associated to the respective sublimation processes are in agreement with the same order for the thermodynamic properties observed in the fusion equilibria and supported by the crystal packing. The 2,6-DPhPy isomer, in which two C−H···N intramolecular interactions and a weak C−H···π intermolecular interaction were found, presents a more flat molecular geometry, a lower density in the crystalline phase, and a lower standard molar enthalpy of sublimation. The 3,5-DPhPy crystal structure shows a π···π intermolecular interaction between a top adjacent folded pyridine and two weak C−H···π intermolecular interactions, and it is the isomer with the highest standard molar enthalpy of fusion and sublimation.…”

Section: Resultsmentioning

confidence: 99%

Energetic and Structural Study of Diphenylpyridine Isomers

et al. 2009

Self Cite

View full text Add to dashboard Cite

The energetic and structural study of three diphenylpyridine isomers is presented in detail. The three isomers, 2,6-, 2,5-, and 3,5-diphenylpyridines, were synthesized via Suzuki-Miyaura methodology based on palladium catalysis, and the crystal structures of the isomers were obtained by X-ray diffraction. The relative energetic stabilities in the condensed and gaseous phases as well as volatilities and structures of the three studied isomers were evaluated, regarding the position of the phenyl groups relative to the nitrogen atom of the pyridine ring. The temperature, standard molar enthalpies, and entropies of fusion were measured and derived by differential scanning calorimetry. The vapor pressures of the considered isomers were determined by a static apparatus based on a MKS capacitance diaphragm manometer. The standard molar enthalpies, entropies, and Gibbs energies of sublimation, at T = 298.15 K, were derived, and the phase diagram near the triple point coordinates were determined for all isomers. The standard (p(o) = 0.1 MPa) molar enthalpies of combustion of all crystalline isomers were determined, at T = 298.15 K, by static bomb combustion calorimetry. The standard molar enthalpies of formation, in the crystalline and gaseous phases, at T = 298.15 K, were derived. The experimental results for the energetics in the gaseous phase of the three compounds were compared and assessed with the values obtained by ab initio calculations at different levels of theory (DFT and MP2) showing that, at this level of theory, the computational methods underestimate the energetic stability, in the gaseous phase, for these molecules. In order to understand the aromaticity in the central ring of each isomer, calculations of NICS (B3LYP/6-311G++(d,p) level of theory) values on the pyridine ring were also performed.

show abstract

Section: Resultsmentioning

confidence: 99%