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

Abstract

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

A detailed exploration of intermolecular interactions in 4-(4-dimethylaminobenzylideneamino)-N-(5-methyl-3-isoxazolyl)benzenesulfonamide and related Schiff bases: Crystal structure, spectral studies, DFT methods, Pixel energies and Hirshfeld surface analysis

“…The singlet located at 8.23 ppm is assigned to the azomethine proton, in accordance with the values reported by similar structures [14]. In 1 H NMR spectra of BA-SMX, the absorption of aromatic ring protons is in the range 6.25-7.80 ppm, in good agreement with literature data [69].…”

“…The assignment of all these modes is shown in Table S2. The bands located at 2966 and 2927 cm − 1 are assigned to the asymmetric CH 3 stretching mode of the methyl groups attached to the amino N atom, in good agreement with the computed values (2933 and 2930 cm −1 ) and with results previously reported [14,68]. The weak band located at 1387 cm −1 in the IR spectra is assigned to the CH 3 symmetric bending mode, with a computed value of 1396 cm −1 (83% of PED).…”

“…In continuation of our interest on Schiff bases [14], in the present work we report the synthesis, crystal structure and spectroscopic study of the Schiff base 4-(4-dimethyl aminobenzylideneamino)-N-(5-methyl-3-isoxazolyl)benzenesulfonamide (for short, BA-SMX). The substance was characterized by IR, Raman, UV-Vis, 1 H and 13 C NMR, electronic spectra and single-crystal X-ray diffraction.…”

In Vitro Degradation of Pure Magnesium―The Effects of Glucose and/or Amino Acid

“…Amino acids and glucose have R-NH 2 and R′-COH groups, respectively. When combined, the chemical reaction between R-NH 2 and R′-COH may be inevitable [ 30 , 46 ]. The protonation of the nitrogen atom of -CH=N- group could positively charge the molecules in aci`d solutions [ 24 ].…”

Synthesis, Antimicrobial Screening, Homology Modeling, and Molecular Docking Studies of a New Series of Schiff Base Derivatives as Prospective Fungal Inhibitor Candidates

“…Nowadays, much attention is paid to the study of Schiff base compounds, not only for their broad range of biological activities—such as antimalarial, antiviral, antitubercular, anticancer, anti-inflammatory, antifungal, and antibacterial properties [1,2,3,4,5,6]—but also because they are widely used as catalyst carriers, optical chemical sensors, thermo-stable materials, metal complexion agents, corrosion inhibitors, and polymer stabilizers [7,8,9,10]. Such Schiff bases, also known as imines or azomethines, can be obtained easily via the condensation reaction between primary amines and carbonyl compounds.…”