Title: Geometry of C—H...O interactions: case of aromatic CH donors
Abstract: SessionsC663 hydrogen bonds of the type C-H⋅⋅⋅O/N and weaker interactions of the type C-H⋅⋅⋅F and C-H⋅⋅⋅π are also considered to have important role in the building of a crystal lattice in the presence of strong hydrogen bonds [3].Different altered modes of hydrogen bonds and weak interactions are known to generate a number of polymorphs of many compounds [4].Polymorphism is a phenomenon of immense importance in pharmaceutical industry [5] and generation of new polymorphs, [5] cocrystals [6] and salts [7] of known APIs are possible using different modes of hydrogen bonds and weaker interactions.Study of polymorphism and cocrystal formation have gained momentum in recent years in the view of intellectual property rights (IPR) as well as in the enhancement of physicochemical properties of the drug molecules for their batter formulations [8].We are interested to investigate the possibility of the formation of new polymorphs and cocrystals of a number of well-known Active Pharmaceutical Ingradients (APIs).Our recent experiments using Fluconazole, Ciprofloxacin, Lamivudine, Lamotrigine and Voriconazole revel that these APIs form new polymorphs or cocrystals or salts when crystallized in the presence of stoichimetric amount of a cocrystal former.The cocrystallization screening experiments have been performed by using both single crystal and powder X-ray diffraction techniques and solid state Raman spectroscopy.We shall highlight our recent results of these experiments and elucidate the crystal structures of new polymorphs of Fluconazole and Lamivudine, new salts of Fluconazole, Ciprofloxacin, Lamivudine and Lamotrigine and a new cocrystal of Voriconazole.Our studies indicate that the presence of a number of weak hydrogen bonds or weaker intermolecular interactions collectively can alter the mode of strong hydrogen bonds and generate new polymorphs, cocrystals and salts of the known APIs.