title: Conformational polymorphs of isobutyl-6-amino-5-cyano-2-methyl-4-phenyl-4H-pyran-3-carboxylate: spectroscopic, structural and DFT approach.
abstract: The crystal structure of a new crystalline phase, polymorph (II) of isobutyl-6-amino-5-cyano-2-methyl-4-phenyl-4H-pyran-3-carboxylate, was accurately determined by single-crystal X-ray diffraction analysis providing a clean identification of polymorphic forms. Comparison with a known phase, referred to as polymorph (I), reveals the type of supramolecular assembly. Inter- and intramolecular hydrogen-bonding interactions exhibit various supramolecular architectures in crystal packing and these variations confirm well the polymorphism in isobutyl-6-amino-5-cyano-2-methyl-4-phenyl-4H-pyran-3-carboxylate (IAPC) crystal structure. Crystal cohesion is achieved by N-H...N, N-H...O and C-H...H-C interactions, responsible for the formation and strengthening of the supramolecular assembly. The objective of this investigation is to study crystalline forms which can offer enhanced physicochemical properties, and also to recognize the molecular orientations between such forms. The conformational polymorphs of IAPC were compared spectroscopically by FT-IR and FT-Raman. The bulk phases were studied by X-ray powder diffraction patterns. External morphology was investigated using scanning electron microscopic images. The molecular interactions were quantified using Hirshfeld surface and fingerprint analysis. Density functional theory (DFT) computations were used to optimize the structure. The optimized structure is further subjected to an analysis of Mulliken population, natural population and electrostatic potential.
authors.affiliation: Department of Chemistry, Annamalai University, Annamalainagar 608 002, India.
authors.forename: A Aditya
authors.initials: AA
authors.lastname: Prasad
authors.affiliation: Department of Chemistry, Annamalai University, Annamalainagar 608 002, India.
authors.forename: C Udhaya
authors.initials: CU
authors.lastname: Kumar
authors.affiliation: Department of Chemistry, Annamalai University, Annamalainagar 608 002, India.
authors.forename: B Arul
authors.initials: BA
authors.lastname: Prakasam
authors.affiliation: Department of Chemistry, Annamalai University, Annamalainagar 608 002, India.
authors.forename: S P
authors.initials: SP
authors.lastname: Meenakshisundaram
mesh_terms: D000586:Amination; D002264:Carboxylic Acids / Q000737:chemistry*; D003460:Crystallization; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008745:Methylation; D008958:Models, Molecular; D011714:Pyrans / Q000737:chemistry*; D011789:Quantum Theory; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman
chemical_list: D002264:Carboxylic Acids; D011714:Pyrans
keywords: Hirshfeld surface analysis; density functional theory; fingerprint analysis; polymorphism; single-crystal X-ray diffraction