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.

Polymorphism and Multicolor Mechanofluorochromism of a D-π-A Asymmetric 4H-Pyran Derivative with Aggregation-Induced Emission Property

“…4 H -Pyran derivatives are a class of D-π-A fluorescent compounds where various electron acceptors and electron donors were easily introduced into the parent unit by simple chemical reactions, which are widely used in the fields of fluorescent sensors, organic electroluminescent diodes, molecular logic gates, etc. − Recently, some 4 H -pyran derivatives have been reported to exhibit polymorphic, AIE, and/or solid-state fluorescence stimulus response properties. − Very recently, some asymmetric 4 H -pyran derivatives were reported to exhibit higher contrast MFC activities than the corresponding symmetric compounds because the low symmetry was conducive to obtaining crystalline structures, which were easily destroyed by external forces . Although several 4 H -pyran derivatives were reported to simultaneously exhibit AIE, polymorphic, and MFC characteristics, as far as we know, these kinds of 4 H -pyran derivatives with multiple crystalline polymorphs have not been reported.…”

“…14−37 Nevertheless, the acquisition of the polymorphs for a compound is hard to be predicted and still depends strongly on the experimental experiences, 38−40 fluorescent sensors, organic electroluminescent diodes, molecular logic gates, etc. 41−44 Recently, some 4H-pyran derivatives have been reported to exhibit polymorphic, 45 AIE, and/or solid-state fluorescence stimulus response properties. 46−55 Very recently, some asymmetric 4H-pyran derivatives were reported to exhibit higher contrast MFC activities than the corresponding symmetric compounds because the low symmetry was conducive to obtaining crystalline structures, which were easily destroyed by external forces.…”

Synthesis, crystal growth, characterization and DFT investigation of a nonlinear optically active cuminaldehyde derivative hydrazone

“…All theoretical calculations were performed using the GAUSSIAN09W (Frisch et al, 2009) program package on a personal computer without any constraints on the geometry using density functional group theory (DFT) with the B3LYP method and the 6-31G(d,p) basis set (Rajasekar et al, 2015;Prasad et al, 2016;Sıdır et al, 2019;Balakrishnan et al, 2020). The optimized structure of the molecule has been visualized using the GAUSSVIEW5.0 molecular visualization (Dennington et al, 2009) program.…”

“…These studies clearly demonstrated that the above hydrazones have superior NLO activity, high transmittance in the visible region and a small HOMO-LUMO energy gap. DFT calculations have been applied to determine the optimized geometry, dipole moment, polarizability, HOMO-LUMO energies at different levels, molecular electrostatic potential, excited state energy, oscillator strength, Mulliken charge population and first-order molecular hyperpolarizability (Prasad et al, 2016;Sıdır et al, 2019;Balakrishnan et al, 2020). These types of materials are chosen since they possess nonlinear optical activity due to large values.…”