resumo
The structure and dynamics of crystalline 4-(dimethylamino) benzaldehyde, 4DMAB, are assessed through INS spectroscopy combined with periodic DFT calculations. The excellent agreement between experimental and calculated spectra is the basis for a reliable assignment of INS bands. The external phonon modes of crystalline 4DMAB are quite well described by the simulated spectrum, as well as the modes involving low-frequency molecular vibrations. Crystal field splitting is predicted and observed for the modes assigned to the dimethylamino group. Concerning the torsional motion of methyl groups, four individual bands are identified and assigned to specific methyl groups in the asymmetric unit. The torsional frequencies of the four methyl groups in the asymmetric unit fall in a region of ca. 190 +/- 20 cm(-1), close to the range of values observed for methyl groups bonding to unsaturated carbon atoms. The hybridization state of the X atom in X-CH3 seems to play a key role in determining the methyl torsional frequency.
palavras-chave
AB-INITIO; FT-RS; SPECTROSCOPY; INS; IR; SPECTRA; RAMAN; TDS
categoria
Chemistry; Materials Science; Metallurgy & Metallurgical Engineering; Physics
autores
Nolasco, MM; Ribeiro-Claro, PJA; Vaz, PD
nossos autores
Mariela Martins Nolasco
Investigador Auxiliar
Paulo Ribeiro-Claro
Professor Associado com Agregação
Pedro Miguel Duarte Vaz
ColaboradorProjectos
CICECO - Aveiro Institute of Materials (UID/CTM/50011/2013)
Projeto de Investigação Exploratória: Mariela Nolasco (IF/01468/2015)
agradecimentos
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)--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 allocation RB15119 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.