Synthesis and structural studies of 4-[(5-methoxy-1H-indole-3-yl)-methylene]-3-methyl-isoxazole-5-one by X-ray crystallography, NMR spectroscopy, and DFT calculations

• DOI: 10.1016/j.molstruc.2011.03.052
• Publication Date: 2011-04-14T20:37:13Z
• Authors: X.H. Zhang; L.Y. Wang; Y.H. Zhan; Y.L. Fu; G.H. Zhai; Z.Y. Wen
• Keywords: Methylene; Monoclinic crystal system; Proton NMR; Chemical shift; Mesogen; Isoxazole

Abstract A merocyanine dye with isoxazolone nucleus: 4-[(5-methoxy-1H-indole-3-yl)-methylene]-3-methyl-isoxazole-5-one ( 1 ) was synthesized and characterized by X-ray diffraction, 1 H NMR, 13 C NMR, IR, UV–Vis spectra and elemental analysis. The crystals are monoclinic, space group P 2 1 /n, with a = 6.4195(16), b = 7.5759(19), c = 25.181(6) A, V = 1217.9(5) A 3 , and Z = 4 (at 298(2) K). Crystal stacking scheme indicates the hydrogen bonds and intermolecular face-to-face π⋯π aromatic stacking interactions generate a unique parallelogram-void supramolecular architecture in solid state of the dye ( 1 ). By DFT calculations, molecular electrostatic potential clearly shows that the formation of hydrogen-bonding interaction [N(2) H(2)⋯O(2) and C(1) H(1A)⋯N(1)] in the crystal structure is between the positive and negative regions. In addition, molecular geometry, tautomeric forms, 1 H NMR and 13 C NMR were calculated by DFT/GIAO (the gauge invariant atomic orbital) methods are in good agreement with the experimental values. The correlation value between experimental 13 C chemical shifts and the calculated magnetic isotropic shielding tensors is 0.9989, and the absolute deviation is 0.2–4.4 based on B3LYP/6-31G * -PCM (the polarizable continuum model) level.