Crystalline Molecular Standards for Low-Frequency Vibrational Spectroscopies

Dampf, Sara J.; Korter, Timothy M.

doi:10.1007/s10762-020-00725-y

Cited by 10 publications

(10 citation statements)

References 67 publications

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“…Since the simulated vibrational spectra are based on a purely harmonic model, the correlation between experiment and theory will always be higher for samples that exhibit little vibrational anharmonicity and this is certainly true for ribavirin. Comparing the current results to the outcomes reported in earlier studies 49 indicates that the enhanced agreement between theory and experiment for ribavirin is largely attributable to the harmonic character of the ribavirin crystal. These findings for ribavirin are similar to that for carvedilol (form II), 50 where the experimental LFRS data shows very little change with cooling and the ss-DFT simulation of the sub-300 cm –1 vibrations provides excellent agreement with the observed peak positions.…”

Section: Discussionsupporting

confidence: 76%

“…The computational approach used in this study is identical to that used in an earlier work on similarly complex organic crystals including biotin, α-lactose monohydrate, and L-cystine. 49 In such studies, the use of a large basis set (greater number of functions) to describe the atomic/molecular electron densities in the crystals produces higher-quality predicted spectra with improved correlations with experiment. 50 Given the inherent trade-off between basis set quality and simulation run time, the def2-TZVP basis set was the largest basis set of practical use for simulations of crystalline ribavirin with generally available computer hardware.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Low-Frequency Vibrational Spectroscopy and Quantum Mechanical Simulations of the Crystalline Polymorphs of the Antiviral Drug Ribavirin

Davis

Korter

2022

Mol. Pharmaceutics

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Crystal polymorphism is a common phenomenon in pharmaceutical solids and a critical issue when considering the formulation of therapeutics since multiple polymorphs may form during drug manufacturing. Low-frequency vibrational spectroscopy is sensitive to polymorphic content, and in this work, terahertz time-domain spectroscopy and low-frequency Raman spectroscopy were utilized in the study of crystalline ribavirin, a widely applicable antiviral. Characteristic spectra with numerous peaks in the sub-200 cm –1 region were obtained of the more common polymorph of ribavirin (Form II). Solid-state density functional theory (ss-DFT) simulations were then used to optimize the crystal structure of this polymorph and calculate the frequencies and spectral intensities of the lattice vibrations in the low-frequency region. The near-harmonic thermal behavior of the sample with cooling enabled excellent agreement between experiment and theory to be achieved, emphasizing the quality of the applied model, and the observed spectral peaks could be assigned to specific atomic motions in the solid. Form I and Form II polymorphs of ribavirin were both investigated with ss-DFT to understand the different aspects governing the relative stabilities of these solids. The ss-DFT simulations of the polymorph energies revealed that Form II is more stable at all temperatures due to a stronger cohesive energy than Form I; however, ribavirin in Form I has a significantly lower conformational energy. The finding of monotropism appears to conflict with the reported enantiotropism of the ribavirin polymorphs but ultimately confirms that crystal defects in the real samples greatly affect the thermodynamic relationship of the crystals.

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Section: Discussionsupporting

confidence: 76%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Low-Frequency Vibrational Spectroscopy and Quantum Mechanical Simulations of the Crystalline Polymorphs of the Antiviral Drug Ribavirin

Davis

Korter

2022

Mol. Pharmaceutics

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“…Here, it is worth noting that several assignments of tartaric acid and lactose have been made previously, [30][31][32][33] with particularly revealing ones given by the Korter group. 34,35 To our knowledge, PABA is yet to be studied in its full crystalline environment. Thus, in the final section of this work, we make a comparative assignment of its room-temperature THz-TDS spectrum using both fully-optimised and volumeconstrained unit cells.…”

Section: Introductionmentioning

confidence: 99%

On the use of a volume constraint to account for thermal expansion effects on the low-frequency vibrations of molecular crystals

Rogers

Radhanpura

Horvat

et al. 2022

Phys. Chem. Chem. Phys.

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“…e reasonable explanation for these popular applications is that THz-TDS is highly sensitive to similar materials with relatively subtle differences [11]. Meanwhile, an increasing number of researches have been done, and it was found that most organic molecules in solid state have rich and distinct spectra in the frequency region among 0.1-6.0 THz [12].…”

Section: Introductionmentioning

confidence: 99%

Experimental and Theoretical Investigations of Terahertz Spectra of the Structural Isomers: Mannose and Galactose

Zhang

Yan

Hao

et al. 2021

Journal of Spectroscopy

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The high-resolution terahertz spectra of the two structural isomers, mannose and galactose, have been measured by terahertz time-domain spectroscopy (THz-TDS) in the range of 0.5–4.0 THz at room temperature. Significant differences between these similar molecules have been found in their THz characteristic spectra, implying that THz-TDS is a powerful tool for identifying isomers. Structural analyses and normal mode calculations of the two systems were performed using solid-state density functional theory (DFT) with the PBE and PW91 density functionals as well as using gas-state DFT with B3LYP hybrid functional. Among these calculations, the solid-state simulated results obtained from the PBE method exhibit a good agreement with the experimentally measured spectra. According to the calculated results of PBE, the observed spectral features were assigned as primarily external lattice translations, deformations, and rotations with lesser contributions due to intramolecular motion of pyranose ring, CH2OH group, and hydroxyl groups.

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Crystalline Molecular Standards for Low-Frequency Vibrational Spectroscopies

Cited by 10 publications

References 67 publications

Low-Frequency Vibrational Spectroscopy and Quantum Mechanical Simulations of the Crystalline Polymorphs of the Antiviral Drug Ribavirin

Low-Frequency Vibrational Spectroscopy and Quantum Mechanical Simulations of the Crystalline Polymorphs of the Antiviral Drug Ribavirin

On the use of a volume constraint to account for thermal expansion effects on the low-frequency vibrations of molecular crystals

Experimental and Theoretical Investigations of Terahertz Spectra of the Structural Isomers: Mannose and Galactose

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