abstract
The dynamics of 2-methoxybenzaldehyde, 4-methoxybenzaldehyde, and 4-ethoxybenzaldehyde in the solid state are assessed through INS spectroscopy combined with periodic DFT calculations. In the absence of experimental data for 4-ethoxybenzaldehyde, a tentative crystal structure, based on its similarity with 4-methoxybenzaldehyde, is considered and evaluated. The excellent agreement between calculated and experimental spectra allows a confident assignment of the vibrational modes. Several spectral features in the INS spectra are unambiguously assigned and torsional potential barriers for the methyl groups are derived from experimental frequencies. The intramolecular nature of the potential energy barrier for methyl rotation about O-CH3 bonds compares with the one reported for torsion about saturated C-CH3 bonds. On the other hand, the intermolecular contribution to the potential energy barrier may represent 1/3 of the barrier height in these systems.
keywords
INELASTIC NEUTRON-SCATTERING; DENSITY-FUNCTIONAL THEORY; AB-INITIO; INTERNAL-ROTATION; FT-RS; X-RAY; SPECTROSCOPY; RAMAN; IR; NMR
subject category
Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering; Physics, Applied; Physics, Condensed Matter
authors
Ribeiro-Claro, PJA; Vaz, PD; Nolasco, MM; Gil, FPSC; de Carvalho, LAEB; Marques, MPM; Amado, AM
our authors
Mariela Martins Nolasco
Assistant Researcher
Paulo Ribeiro-Claro
Associate Professor with Aggregation
Pedro Miguel Duarte Vaz
CollaboratorProjects
CICECO - Aveiro Institute of Materials (UID/CTM/50011/2013)
Projeto de Investigação Exploratória: Mariela Nolasco (IF/01468/2015)
acknowledgements
This work received financial support from the Portuguese Foundation for Science and Technology (FCT)-project CICECO, Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (UID/CTM/50011/2013) and Unidade de I&D Quimica-Fisica Molecular (UIDB/00070/2020)-financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. Experiments at the ISIS Neutron and Muon Source were supported by beamtime allocations RB11177 and RB14115 from the Science and Technology Facilities Council. FCT is gratefully acknowledged for a researcher contract to M.M.N. (IF/01468/2015) under the program IF 2015.