Vangala, Venu R.Chow, P.S.Schreyer, M.Lau, G.Tan, R.B.H.2016-01-082016-01-082015-12-23Vangala VR, Chow PS, Schreyer M, Lau G and Tan RBH (2016) Thermal and in situ x-ray diffraction analysis of a dimorphic co-crystal 1:1 caffeine-glutaric acid. Crystal Grown and Design. 16(2): 578-586.http://hdl.handle.net/10454/7646YesSpurred by the enormous interest in co-crystals from the pharmaceutical industry, many novel co-crystals of active pharmaceutical ingredients have been discovered in recent years and this has in turn led to an increasing number of reports on polymorphs of co-crystals. Hence, a thorough characterization and understanding of co-crystal polymorphs is a valuable step during drug development. The purpose of this study is to perform in situ structural analysis and to determine thermodynamic stability of a dimorphic co-crystal system, 1:1 caffeine-glutaric acid (CA-GA, Forms I and II). We performed thermal and structural characterizations by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), hot-stage microscopy (HSM), slurry and in situ variable temperature X-ray diffraction (VTXRD). For completeness, we have also re-determined crystal structures of CA-GA Forms I and II at 180 K using single crystal X-ray diffraction. Our results revealed that Form II is stable and Form I is metastable at ambient conditions. Further, the results suggest that the dimorphs are enantiotropically related and the transition temperature is estimated to be 79 Celcius degrees.enThis document is the Accepted Manuscript version of a Published Work that appeared in final form in Crystal Grown and Design, copyright © American Chemical Society after peer-review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.cgd.5b00798.X-ray diffraction analysisDimorphic co-crystalCaffeine-glutaric acidpolymorphsdrug developmentstructural analysisArticlehttps://doi.org/10.1021/acs.cgd.5b00798Unspecified