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Testing the Sensitivity of Terahertz Spectroscopy to Changes in Molecular and Supramolecular Structure: A Study of Structurally Similar Cocrystals

Parrott, EPJ; Zeitler, JA; Friscic, T; Pepper, M; Jones, W; Day, GM; Gladden, LF; (2009) Testing the Sensitivity of Terahertz Spectroscopy to Changes in Molecular and Supramolecular Structure: A Study of Structurally Similar Cocrystals. CRYST GROWTH DES , 9 (3) 1452 - 1460. 10.1021/cg8008893.

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Abstract

Terahertz time-domain-spectroscopy (THz-TDS) has emerged as a versatile spectroscopic technique, and an alternative to powder X-ray diffraction in the characterization of molecular crystals. We tested the ability of terahertz spectroscopy to distinguish between chiral and racemic hydrogen-bonded cocrystals that are similar in molecular and supramolecular structure. Terahertz spectroscopy readily distinguished between the isostructural cocrystals of theophylline with chiral and racemic forms of malic acid which are almost identical in molecular structure and supramolecular architecture. Similarly, the cocrystals of theophylline with chiral and racemic forms of tartaric acid, which are similar at the molecular level but dissimilar in crystal packing, were distinguished unequivocally. The investigation of the same cocrystals using X-ray powder diffraction and Raman spectroscopy suggested that THz-TDS is comparable in sensitivity to diffraction methods and more sensitive than Raman spectroscopy to changes in cocrystal architecture. The differences in spectra acquired by THz-TDS could be further enhanced by cooling the samples to 109 K.

Type:Article
Title:Testing the Sensitivity of Terahertz Spectroscopy to Changes in Molecular and Supramolecular Structure: A Study of Structurally Similar Cocrystals
DOI:10.1021/cg8008893
Keywords:X-RAY-DIFFRACTION, TIME-DOMAIN SPECTROSCOPY, SOLID-STATE NMR, DISTRIBUTED MULTIPOLE ANALYSIS, TO-SINGLE-CRYSTAL, PULSED SPECTROSCOPY, CARBOXYLIC-ACIDS, CO-CRYSTAL, FORM-II, CARBAMAZEPINE
UCL classification:UCL > School of BEAMS > Faculty of Engineering Science > Electronic and Electrical Engineering

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