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DFT-Assisted Polymorph Identification from Lattice Raman Fingerprinting.

ABSTRACT: A combined experimental and theoretical approach, consisting of lattice phonon Raman spectroscopy and density functional theory (DFT) calculations, is proposed as a tool for lattice dynamics characterization and polymorph phase identification. To illustrate the reliability of the method, the lattice phonon Raman spectra of two polymorphs of the molecule 2,7-dioctyloxy[1]benzothieno[3,2-b]benzothiophene are investigated. We show that DFT calculations of the lattice vibrations based on the known crystal structures, including many-body dispersion van der Waals (MBD-vdW) corrections, predict experimental data within an accuracy of ?5 cm^-1 (?0.6 meV). Due to the high accuracy of the simulations, they can be used to unambiguously identify different polymorphs and to characterize the nature of the lattice vibrations and their relationship to the structural properties. More generally, this work implies that DFT-MBD-vdW is a promising method to describe also other physical properties that depend on lattice dynamics like charge transport.

SUBMITTER: Bedoya-Martinez N

PROVIDER: S-EPMC5545759 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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DFT-Assisted Polymorph Identification from Lattice Raman Fingerprinting.

Bedoya-Martínez Natalia N Schrode Benedikt B Jones Andrew O F AOF Salzillo Tommaso T Ruzié Christian C Demitri Nicola N Geerts Yves H YH Venuti Elisabetta E Della Valle Raffaele Guido RG Zojer Egbert E Resel Roland R

The journal of physical chemistry letters 20170726 15

A combined experimental and theoretical approach, consisting of lattice phonon Raman spectroscopy and density functional theory (DFT) calculations, is proposed as a tool for lattice dynamics characterization and polymorph phase identification. To illustrate the reliability of the method, the lattice phonon Raman spectra of two polymorphs of the molecule 2,7-dioctyloxy[1]benzothieno[3,2-b]benzothiophene are investigated. We show that DFT calculations of the lattice vibrations based on the known c ...[more]

PMID: 28731723

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Project description:Highlights • 10 different astaxanthin (AST) geometrical isomers were analyzed by Raman spectroscopy.• Raman spectroscopy can distinguish all the geometrical isomers of AST molecules.• Structures and vibrational modes of all the AST isomers are obtained due to DFT calculations. Astaxanthin is a carotenoid widely used in food additives, nutritional product and medicines, which shows many physiological functions such as antioxidant, anti-inflammatory, anti-hypertensive and anti-diabetic activities. It has been recognized that astaxanthin has all-trans and nine cis isomers, and these geometrical isomers have very different biological activities. The process of selective enrichment, metabolism and isomerization of astaxanthin in animals remains to be studied. Therefore, identifying isomers and obtaining their structural parameters are important for understanding the active mechanism of different molecular isomers. Although the traditional methods such as high-performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR) spectroscopy can be used to distinguish these isomers, these methods generally require considerable testing time, cost, sample volume, and hardly be applied in vivo. In this work, Raman spectroscopy combined with density functional theory (DFT) calculation was introduced to study different geometrical isomers of astaxanthin. The theoretical and experimental Raman spectra are in agreement, and we have demonstrated that all the known ten geometrical isomers of astaxanthin can be readily distinguished using this spectroscopic approach. The astaxanthin molecular vibrational modes, geometric structures, energies of ten geometric isomers are systematically scrutinized. Moreover, a lot of structural and Raman problems unsolved previously have been solved by the DFT-based spectral analysis. Therefore, this work provides an effective way for identification of different astaxanthin geometrical isomers, and may have important significance for promoting the research of astaxanthin isomers on biological property mechanisms and related applications in food molecular science.

Dataset Information

DFT-Assisted Polymorph Identification from Lattice Raman Fingerprinting.

Publications

DFT-Assisted Polymorph Identification from Lattice Raman Fingerprinting.

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