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

abstract

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.

keywords

INELASTIC NEUTRON-SCATTERING; DOT-O INTERACTIONS; HYDROGEN-BOND; FLUORESCENCE-SPECTRA; MOLECULAR-CRYSTALS; RAMAN; ROTATION; IR; SPECTROSCOPY; S-0

subject category

Biochemistry & Molecular Biology; Chemistry

authors

Nolasco, MM; Araujo, CF; Vaz, PD; Amado, AM; Ribeiro-Claro, P

our authors

acknowledgements

This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. A.M.A. acknowledges financial support given by POCentro, COMPETE 2020, Portugal 2020, European Community through the FEDER and FCT to Unidade de I&D Quimica-Fisica Molecular of the University of Coimbra (UIDB/00070/2020). FCT is gratefully acknowledged for funding a PhD grant to C.F.A. (SFRH/BD/129040/2017) and a researcher contract to M.M.N. (IF/01468/2015) under the program IF 2015.

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