Supramolecular self-assembly of a new multi-conformational Schiff base through hydrogen bonds: Crystal structure, spectroscopic and theoretical investigation

M. ROCHA; A. DI SANTO; G. A. ECHEVERRÍA; O. E. PIRO; F. D. CUKIERNIK; S. E. ULIC; D. M. GIL

JOURNAL OF MOLECULAR STRUCTURE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2017 vol. 1133 p. 24 - 36

0022-2860

The compound 4-(4-dimethylaminobenzylidene)aminoacetophenone was synthesized by condensationof 4-aminoacetophenone and 4-(dimethylamino) benzaldehyde in ethanol. This compound was characterizedby CG-MS, infrared, Raman, UV-Vis, 1H and 13C NMR spectroscopy. The crystal structure wassolved by single-crystal X-ray diffraction methods. The crystallographic data reveals that there are fourindependent molecules per asymmetric unit, that mainly differ from one another in rotations around thesigma-bond of the azomethine N-atom with the phenyl ring. A detailed analysis of the intermolecular interactionsin the four conformers of the compound has been performed using Hirshfeld surfaces andtheir associated two-dimensional fingerprint plots. The optimized geometrical parameters and calculatedspectroscopic features obtained by quantum chemical calculations at B3LYP method show a verygood agreement with the experimental data. Moreover, Natural Bond Orbital (NBO) analysis confirms thestrong hyper-conjugative LP N(n1)/ s* C(n9)eH interaction between the lone pair located in the Natomof the azomethine group and the CeH bond. Liquid crystalline properties of the Schiff base werestudied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and Powder Xraydiffraction techniques. Mesomorphic behaviour was observed in this unsymmetrical azomethine.Based on POM and DSC measurements, the hexatic Smetic B phase was detected.