Vibrational Dynamics of Crystalline 4-Phenylbenzaldehyde from INS Spectra and Periodic DFT Calculations

• Autor(a) principal: Nolasco, Mariela M.
• Data de Publicação: 2020
• Outros Autores: Araujo, Catarina F., Vaz, Pedro D., Amado, Ana M., Ribeiro-Claro, Paulo J. A.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10316/106485; https://doi.org/10.3390/molecules25061374
• topic: inelastic neutron scattering; density functional theory; vibrational assignment; molecular crystal; torsional potential; C-H···O hydrogen bonds; Biphenyl Compounds; Molecular Structure; Spectrophotometry, Infrared; Models, Molecular

The present work emphasizes the value of periodic density functional theory (DFT) calculations in the assessment of the vibrational spectra of molecular crystals. Periodic calculations provide a nearly one-to-one match between the calculated and observed bands in the inelastic neutron scattering (INS) spectrum of crystalline 4-phenylbenzaldehyde, thus validating their assignment and correcting previous reports based on single molecule calculations. The calculations allow the unambiguous assignment of the phenyl torsional mode at ca. 118-128 cm-1, from which a phenyl torsional barrier of ca. 4000 cm-1 is derived, and the identification of the collective mode involving the antitranslational motion of CH···O bonded pairs, a hallmark vibrational mode of systems where C-H···O contacts are an important feature.