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Influence of crystal packing on the mechanism of decomposition of the acetonitrile-solvated co-crystal of piroxicam and succinic acid

DOI: 10.1021/acs.cgd.9b01189 DOI Help

Authors: Xiaojiao Liu (University of Edinburgh) , Chiu C. Tang (Diamond Light Source) , Elena V. Boldyreva (Boreskov Institute of Catalysis, Siberian Branch of Russian Academy of Sciences; Novosibirsk State University) , Colin R. Pulham (University of Edinburgh)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Crystal Growth & Design

State: Published (Approved)
Published: November 2019
Diamond Proposal Number(s): 20626

Abstract: Variable-temperature single-crystal and powder X-ray diffraction techniques have been used to study the thermal and mechanical decomposition of the acetonitrile solvate of the co-crystal formed between piroxicam and succinic acid (PRXSA-ACN). The results show that the thermal expansion behavior of PRXSA-ACN is highly anisotropic and can be correlated with structural features of the crystal lattice. Thermally-induced desolvation of PRXSA-ACN led initially to the formation of the α-form of piroxicam and the 1:1 piroxicam:succinic acid co-crystal (PRXSA), and this can be rationalized on the basis of the crystal structure of PRXSA-ACN and its thermal expansion behavior. Subsequent decomposition of PRXSA produced amorphous succinic acid and the thermodynamically more stable β-form of piroxicam. The α- and β-forms co-existed up until the melting point of the α-form, at which point the sample recrystallized to give the β-form of piroxicam. Mechanical treatment (light grinding) of PRXSA-ACN resulted in mild structural damage to the crystal structure and this led to subsequent desolvation.

Journal Keywords: Piroxicam; Co-crystal; Thermal Expansion; Thermal Desolvation; Mechanical Desolvation; Thermal Decomposition

Subject Areas: Chemistry

Instruments: I11-High Resolution Powder Diffraction