Terahertz Vibrational Modes of Crystalline Salicylic Acid by Numerical Model Using Periodic Density Functional Theory

Saito, Shigeki; Inerbaev, Talgat M.; Mizuseki, Hiroshi; Igarashi, Nobuaki

doi:10.1143/jjap.45.4170

Cited by 20 publications

(8 citation statements)

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“…They showed that the simulated THz spectrum of crystalline salicylic acid [232] has lattice modes at the lowest frequencies, intermolecular modes at intermediate frequencies, and intramolecular modes at the highest THz frequencies. They performed similar simulations on the organic salt DAST [233] with emphasis on the difference between isolated-molecule and solid-state simulation, and on lactose monohydrate with special emphasis on the role of crystal water [234], and on beta-D-glucopuranose [235].…”

Section: Static Thz-tds Of Solid-state Materialsmentioning

confidence: 99%

Terahertz spectroscopy and imaging – Modern techniques and applications

Jepsen

Cooke

Koch

2010

Laser & Photonics Reviews

1,745

977

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Over the past three decades a new spectroscopic technique with unique possibilities has emerged. Based on coherent and time-resolved detection of the electric field of ultrashort radiation bursts in the far-infrared, this technique has become known as terahertz time-domain spectroscopy (THz-TDS). In this review article the authors describe the technique in its various implementations for static and time-resolved spectroscopy, and illustrate the performance of the technique with recent examples from solid-state physics and physical chemistry as well as aqueous chemistry. Examples from other fields of research, where THz spectroscopic techniques have proven to be useful research tools, and the potential for industrial applications of THz spectroscopic and imaging techniques are discussed.

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Section: Static Thz-tds Of Solid-state Materialsmentioning

confidence: 99%

Terahertz spectroscopy and imaging – Modern techniques and applications

Jepsen

Cooke

Koch

2010

Laser & Photonics Reviews

1,745

977

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“…[10][11][12] Crystalline APIs also have unique phonon modes, and as such, polymorphic forms of solid formulations have different THz spectra. [13][14][15][16] In addition, the absence of distinct modes in amorphous or liquid crystalline forms has been demonstrated.…”

Section: -7)mentioning

confidence: 99%

A Novel Analytical Method for Pharmaceutical Polymorphs by Terahertz Spectroscopy and the Optimization of Crystal Form at the Discovery Stage

et al. 2010

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Crystal polymorphs are defined as substances that are chemically identical but exist in more than one crystal form, and generally differ in physicochemical properties. The polymorphism is a common phenomenon among pharmaceuticals. It has been shown that about 80% of active pharmaceutical ingredients (API) have polymorphs. 1,2)The optimization of polymorphic forms of an API is an important area of physicochemical research in drug discovery. The impact of polymorphs has been widely reported in the literatures, affecting such properties as dissolution rates, solubility, bioavailability and manufacturability. 3-7)The detection of polymorphs in drug discovery and manufacturing process is very important for assuring sufficient quality of the API. Powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), IR spectroscopy, Raman spectroscopy and solid state NMR measurement are generally applied for polymorph analysis of APIs. Although most of polymorphs are identifiable by these analytical techniques, there are some difficult cases to identify.In a previous paper, 8) we reported on remarkably similar polymorphs, forms A and B of Compound A, which is a novel drug for the treatment of osteoporosis. They were discriminated only by high-resolution powder X-ray diffractometry and thermally stimulated current (TSC) measurements. In particular, the TSC technique was useful for the discrimination of Compound A polymorphs, since both forms gave completely different TSC patterns.The terahertz (THz) region of the electromagnetic spectrum lies between the infrared and millimeter wave regions around 0.3 to 10 THz. THz spectroscopic analysis has been proposed as an analytical technique for crystal polymorphs because of the typical energies characterizing intermolecular interactions in a crystal lattice correspond to the THz region.9) The assignment of spectral features in this regime is still subject to scientific debate and several experiments have been discussed. [10][11][12] Crystalline APIs also have unique phonon modes, and as such, polymorphic forms of solid formulations have different THz spectra. [13][14][15][16] In addition, the absence of distinct modes in amorphous or liquid crystalline forms has been demonstrated. [17][18][19] Thus, THz spectroscopy is thought to be an effective tool for readily discriminating polymorph, even when their crystalline structures are quite similar.In this paper, we demonstrate THz spectroscopy as a novel analytical procedure for the determination of pharmaceutical polymorphs. We have shown that polymorphs of tolbutamide, carbamazepine and Compound A show slight different THz absorption spectra from each other and the second derivative of the THz absorption spectrum is an enormously beneficial tool for discerning different polymorphs.After the polymorph characterization, the optimization of the crystal form is an important step in the development of an API. To avoid the polymorph trouble during manufacturing and storage such as in the Ritonavir nightmare, 20,21) from the view...

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“…Therefore, calculations of the crystalline vibrations of a BBO-crystal unit cell in the THz range, based on first principles, were performed using the density-functional-theory method. The lattice vectors were fixed for the optimization of the atomic positions [19][20][21]. The calculated dipole derivatives are shown in Fig.…”

Section: Article In Pressmentioning

confidence: 99%