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Li Y, Xu L, Ouyang J, Lei J, Hu J, Xing X, Chen P, Li J, Zhong C, Yang B, Li H. Harmonic and anharmonic studies on THz spectra of two vanillin polymorphs. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2024; 309:123869. [PMID: 38198992 DOI: 10.1016/j.saa.2024.123869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 12/05/2023] [Accepted: 01/05/2024] [Indexed: 01/12/2024]
Abstract
Polymorphism commonly exists in organic molecular crystals. The fingerprint features in low-frequency vibrational range are important information reflecting different intermolecular interactions of polymorphs. Interpreting these features is very helpful to understand vibrational property of polymorphs and reveal the thermodynamic stability. In this work, the low-frequency vibrations of form I and II of vanillin are investigated using terahertz time-domain spectroscopy. Static DFT calculation and ab initio molecular dynamics (AIMD) are employed to interpret their low-frequency vibrations of both forms in harmonic and anharmonic ways, respectively. Their low-frequency vibration characteristics in harmonic calculations are discussed, and anharmonic mode couplings between OH bond stretch and the stretching and bending motion of hydrogen bonds are uncovered. Moreover, the thermodynamic energies including electronic potential energy and vibrational/kinetic energy arising from nuclear motions are calculated. The result reveals that the stability order of the two forms is mainly dependent on their electric potential energy difference.
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Affiliation(s)
- Yin Li
- School of Physics and Materials Science, Nanchang University, Xuefu Avenue 999, Nanchang City 330031, China.
| | - Li Xu
- School of Chemistry, Biology and Materials Science, East China University of Technology, Guanglan Avenue 418, Nanchang City 330013, China
| | - Jinbo Ouyang
- School of Chemistry, Biology and Materials Science, East China University of Technology, Guanglan Avenue 418, Nanchang City 330013, China.
| | - Jiangtao Lei
- Institute of Space Science and Technology, Nanchang University, Xuefu Avenue 999, Nanchang City 330031, China
| | - Jun Hu
- School of Mechatronics & Vehicle Engineering, East China Jiaotong University, Nanchang, Jiangxi 330013, China
| | - Xiaohong Xing
- School of Chemistry, Biology and Materials Science, East China University of Technology, Guanglan Avenue 418, Nanchang City 330013, China
| | - Peng Chen
- School of Chemistry, Biology and Materials Science, East China University of Technology, Guanglan Avenue 418, Nanchang City 330013, China
| | - Jiaqing Li
- School of Physics and Materials Science, Nanchang University, Xuefu Avenue 999, Nanchang City 330031, China
| | - Changqing Zhong
- School of Physics and Materials Science, Nanchang University, Xuefu Avenue 999, Nanchang City 330031, China
| | - Bo Yang
- School of Physics and Materials Science, Nanchang University, Xuefu Avenue 999, Nanchang City 330031, China
| | - Heng Li
- Fujian Provincial Key Laboratory of Semiconductors and Applications, Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Department of Physics, Xiamen University, Xiamen 361005, China; Jiujiang Research Institute, Xiamen University, Jiujiang 332000, China
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Yang B, Li Y, Lei J, Cai M, Hu Z, Shen Y, Deng X. Dehydration kinetics and mechanism of the stable isonicotinamide hydrate revealed by terahertz spectroscopy and DFT calculation. Int J Pharm 2023; 638:122893. [PMID: 36990167 DOI: 10.1016/j.ijpharm.2023.122893] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 03/13/2023] [Accepted: 03/23/2023] [Indexed: 03/30/2023]
Abstract
The dehydration behavior of pharmaceutical hydrates has a great influence on its physiochemical properties such as stability, dissolution rate and bioavailability. However, how the intermolecular interactions vary during dehydration process remains elusive. In this work, we employed terahertz time-domain spectroscopy (THz-TDS) to probe the low-frequency vibrations and the dehydration process of isonicotinamide hydrate I (INA-H I). Theoretical solid-state DFT calculation was conducted to reveal its mechanism. Vibrational modes which are responsible for the THz absorption peaks were decomposed for better understanding the characters of these low-frequency modes. The result suggests translational motion is the dominant component for water molecules in THz region. Evolution of the THz spectrum of INA-H I during dehydration provides direct evidence of the variations of crystal structure. Based on the THz measurements, a two-step kinetics mode including first-rate reaction and three-dimensional nuclei growth is proposed. And we nure that the low-frequency vibrations of water molecules are the origin of dehydration process of hydrate.
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