Determination of Drug Polymorphs by Laser Raman Spectroscopy. I. Ampicillin and Griseofulvin

Bellows, James C.; Chen, Freeman P.; Prasad, Paras N.

doi:10.3109/03639047709055624

Cited by 20 publications

(7 citation statements)

References 8 publications

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“…5-120 cm À1 ) of the Raman spectrum of crystalline griseofulvin (Fig. 1e) exhibits three distinct peaks at 34, 59 and 87 cm À1 , which are associated with lattice vibrations and are in agreement with earlier reports by Bellows et al [26]. Disrupting the long-range order of griseofulvin resulted in the disappearance of the crystalline peaks and the appearance of a broad peak with a maximum at 10 cm À1 (Fig.…”

Section: Characterisation Of Griseofulvin Tabletssupporting

confidence: 88%

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Use of low-frequency Raman spectroscopy and chemometrics for the quantification of crystallinity in amorphous griseofulvin tablets

Mah

Fraser

Reish

et al. 2015

Vibrational Spectroscopy

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Section: Characterisation Of Griseofulvin Tabletssupporting

confidence: 88%

“…Low-frequency Raman spectroscopy was used in the 1970s to examine various materials including APIs [26]. These experiments used visible excitation sources with scanning spectrographs and photomultiplier tube detection.…”

Section: Introductionmentioning

confidence: 99%

Use of low-frequency Raman spectroscopy and chemometrics for the quantification of crystallinity in amorphous griseofulvin tablets

Mah

Fraser

Reish

et al. 2015

Vibrational Spectroscopy

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“…Infrared and Raman vibrational spectra are known to differentiate polymorphs, at least in favorable cases, 54 and both of these methods can provide evidence for hydrogen bonding. The N-H stretching mode in secondary aromatic amines usually appears near 3450 cm Ϫ1 and this is not strongly affected by neighboring electron withdrawing groups unless they participate in a hydrogen bond to the amino hydrogen.…”

Section: Infrared and Resonance Raman Spectramentioning

confidence: 99%

Crystal polymorphism in pendimethalin herbicide is driven by electronic delocalization and changes in intramolecular hydrogen bonding. A crystallographic, spectroscopic and computational study

Stockton¹,

Godfrey²,

Hitchcock³

et al. 1998

J. Chem. Soc., Perkin Trans. 2

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Pendimethalin, N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine, is a potent herbicide that exists in two differently coloured polymorphic crystal habits. Triclinic pendimethalin I (P1 ¯) is the orange-coloured thermodynamically stable form, whereas monoclinic pendimethalin II (P2 1 /c) is a bright-yellow metastable form. The latter is normally produced first upon cooling the molten chemical, whereas the orange form is formed by a polymorphic phase transition which occurs slowly upon long term storage of the yellow form at temperatures below its melting point. Such phase transitions are rapidly revealed by calorimetry. The crystal structures of the polymorphs have been determined using single crystal X-ray diffraction. Solid state NMR spectroscopy, vibrational spectroscopy and UV-VIS spectroscopy were applied to further study the nature of the polymorphism in terms of intra-and inter-molecular properties. Solid state CP-MAS 13 C NMR spectroscopy was shown to be the method of choice for quantitative analysis of polymorphic mixtures. The differences in spectral properties and crystal habits were investigated by computational methods which included molecular exciton, molecular orbital and molecular mechanics calculations. The dramatic colour change from yellow to orange-red during the polymorphic transition is discussed in terms of competing inter-and intra-molecular electronic effects. The driving force for the yellow (II) to orange (I) polymorphic transition is attributed to the change in the electronic delocalization achieved from shortening, strengthening, and partially straightening the 'bent' hydrogen bond between the secondary amino hydrogen and an oxygen of the 6Ј-nitro group. This results in increased overlap between the amino nitrogen's lone pair and the -electron orbitals of the aromatic ring. The calculated lattice stabilization energy due to this process is 4 to 5 kcal mol ؊1 , and the relative lattice energies are consistent with the observed stabilities of the polymorphs. The slow kinetics of the polymorphic transition are largely governed by the steric interaction of the 1-ethylpropyl side chain and the two nitro groups. During crystallization, the more compact side chain conformation required to form the energetically more stable orange (I) polymorph appears to be more difficult to achieve than that required for the yellow (II) polymorph.

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“…The first-order lattice or inter-molecular modes observed in Raman spectra typically occur at frequencies below 200 cm À1 . 5,6 Lattice modes include translational and librational vibrations that are very sensitive to structural disorder and polymorphism. Intra-molecular deformation, rocking, wagging, breathing, and stretching modes, which typically lie in the frequency range above 200 cm À1 , 7 are also sensitive to changes in the local crystal field caused by disorder or polymorph formation.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic and X-Ray Diffraction Study of Structural Disorder in Cryomilled and Amorphous Griseofulvin

et al. 2011

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Structural disorder induced by cryogenic milling and by heating to the amorphous phase in the active pharmaceutical ingredient Griseofulvin has been studied using Raman spectroscopy, X-ray powder diffraction (XRPD), and fluorescence spectroscopy. A broad, exciting-frequency-independent scattering background in the Raman spectra and changes in intensities and splitting of some of the Raman lines due to lattice and molecular modes have been observed. In the cryomilled samples this strong background is deconvoluted into two components: one due to lattice disorder induced by cryomilling and the other due to Mie scattering from nanosized crystallites. A single-component background scattering attributed to lattice disorder is seen in the Raman spectrum of the amorphous sample. Fluorescence measurements showed an intrinsic fluorescence signal in as-received Griseofulvin that does not correspond to the inelastic background in the Raman spectra and, moreover, decreases in intensity upon cryomilling, thus excluding an assignment of the Raman background intensity to impurity- or molecular-defect-induced fluorescence. Wide-angle XRPD measurements on cryomilled Griseofulvin shows a broad two-component background consistent with the background-scattering component in the Raman data associated with lattice disorder, but at longer correlation lengths. Persistence of this disorder to even longer lengths is evident in small-angle synchrotron XRPD data on micronized Griseofulvin taken as a function of temperature from the crystalline to the amorphous phase.

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Determination of Drug Polymorphs by Laser Raman Spectroscopy. I. Ampicillin and Griseofulvin

Cited by 20 publications

References 8 publications

Use of low-frequency Raman spectroscopy and chemometrics for the quantification of crystallinity in amorphous griseofulvin tablets

Use of low-frequency Raman spectroscopy and chemometrics for the quantification of crystallinity in amorphous griseofulvin tablets

Crystal polymorphism in pendimethalin herbicide is driven by electronic delocalization and changes in intramolecular hydrogen bonding. A crystallographic, spectroscopic and computational study

Spectroscopic and X-Ray Diffraction Study of Structural Disorder in Cryomilled and Amorphous Griseofulvin

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