Structural, spectroscopic and first-principles studies of new aminocoumarin derivatives

Abstract

The new aminocoumarin derivatives 3-[1-(3-hydroxyanilino)ethylidene]-3Hchromene-2,4-dione, (1), 3-[1-(4-hydroxyanilino)ethylidene]-3H-chromene-2,4dione, (2), and 3-[1-(2-hydroxyanilino)ethylidene]-3H-chromene-2,4-dione, (3), all C 17 H 13 NO 4 , were synthesized by reacting an equimolar amount of 3-acetyl-4hydroxycoumarin and the corresponding aminophenol in absolute ethanol. Structural and spectroscopic analysis of these phases revealed that derivatives (1) and (2) are isomers of previously reported (3) [Brahmia et al. (2013). Acta Cryst. E69, o1296]. The crystal structures of meta derivative (1) and para derivative (2) were ab initio determined from powder X-ray diffraction data using the direct-space approach. Both (1) and (2) adopt the orthorhombic space group P2 1 2 1 2 1 . These isomers show hydrogen bonds and richstacking, together with Á Á ÁH interactions, which are built by conjugated systems of coumarin and phenol rings. In the crystalline lattice, the packing of (1) and (3) are mainly stabilized through O-HÁ Á ÁO hydrogen bonding between neighbouring coumarin molecules, while hydrogen bonds between coumarin and water molecules build the stable crystal structure of derivative (2). A big similarity in the skeletons of the IR spectra of these isomers was noticed. Derivative (2) exhibits two weak bands which were not present in the spectra of the other two derivatives, at 2370 and 2948 cm À1 , which can be assigned to the O-H vibrations of the solvent (H 2 O) trapped in the structure of (2). These aminocoumarin derivatives display absorption maxima in the visible region, attributed todelocalization involving the whole electronic system of the compounds with a considerable charge-transfer character originating from the aminophenyl ring and pointing towards the coumarin system which is characterized by a high electron-accepting character. Additionally, the isolated molecular ground-state geometries were optimized at the PBE0/TZP level and the electronic properties, molecular electrostatic potential and Hirshfeld charges were determined.

Introductory Chapter: Crystalline Materials and Applications

“…As part of the crystalline materials research for biologically active molecules, groups of organic heterocycles appear, such as coumarin derivatives [11,12], which can be found in the plant kingdom. The synthesis and structural characterization work carried out on these materials constitutes a vast field of research, in which a large number of laboratories are involved in the world.…”