Intramolecular hydrogen bonding in N-salicylideneaniline: FT-IR spectrum and quantum chemical calculations

Moosavi-Tekyeh, Zainab; Dastani, Najmeh

doi:10.1016/j.molstruc.2015.09.001

Cited by 27 publications

(11 citation statements)

References 87 publications

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“…According to Salman et al, the carbonyl group of the keto-amine tautomer shows intense absorption bands at 1624-1633 cm −1 [32]. In accordance with published data showing that stretching of the C=N bond occurs in the 1614-1623 cm −1 region, the absorption at 1610 cm −1 was attributed to the C=N group [5,18,32,33]. In addition, the occurrence of a zwitterion form decreases the wavenumber of this absorption since protonation of the nitrogen would increases the effective mass.…”

Section: These Facts Indicated That the C-n And C-o Bonds Have Intermsupporting

confidence: 78%

“…Therefore, although discovered a long time ago, study of proton tautomerization is a major scientific issue [8][9][10][11]. In this context, the NH-form in the imine-phenol/keto-amine tautomerization of salicylideneaniline shown in Figure 1 has been widely studied [12][13][14][15][16][17][18] since Ogawa et al first provided X-ray crystallographic evidence of its existence [12,17]. The OH-form of salicylideneaniline is generally more stable than the NH-form and there are numerous studies on the properties involving the chromism of the OH-form of such molecules [19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

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NH-form of a threonine-based Schiff base in the solid state

Oketani

Takahashi

Hoquante

et al. 2019

Journal of Molecular Structure

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Stable NH-form of the threonine-based Schiff base 4, (2S,3R)-3-((tert-butyldimethylsilyl)oxy)-2-(((E)-(2-hydroxynaphthalen-1-yl)methylene)amino)butanamide, was synthesized and characterized in the crystalline state by means of IR spectroscopy and X-ray crystallographic analysis. This is the first X-ray determination of an amino acid-based Schiff base that was locked in the NH-form. Comparison of the characteristic bond lengths based on the X-ray structure of 4 with previously reported NH-forms of other Schiff bases revealed that the structure of 4 was a hybrid of two canonical structures, namely, zwitterion and quinoid, contributing to the resonance. It was also found that 4 exist in the OH-form in solution and its phenolic proton is wellconstrained via intramolecular hydrogen bonding with the imine functionality.

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Section: These Facts Indicated That the C-n And C-o Bonds Have Intermsupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

NH-form of a threonine-based Schiff base in the solid state

Oketani

Takahashi

Hoquante

et al. 2019

Journal of Molecular Structure

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“…The new peak is likely to be a peak observed at 1656 cm−1 for different Schiff bases using the resonance Raman spectroscopy and seen as a shoulder at 1660 cm−1 in the infrared spectra [10]. A band in this spectral region has been found at 1651 cm−1 in the infrared spectra of SA in a mixed isopentane/methylcyclohexane solvent after flash photolysis [7] and at 1675 cm−1 in the IR spectrum of SA in CCl 4 solution [55]. These spectral features have been assigned to the C=O stretching mode of the trans-keto tautomer of the SA molecule [7,10,55].…”

Section: Discussionmentioning

confidence: 99%

A Spectroscopic Study of Tautomeric Equilibrium of Salicylideneaniline in ZSM-5 Zeolites

2019

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Salicylideneaniline (SA) sorbed in cation-exchanged M-ZSM-5 (M = H+, Li+, Na+, K+, Rb+, Cs+ and Zn2+) zeolites was studied by spectroscopic techniques assisted by quantum-chemical calculations. The nature of extra-framework cations present in the zeolite void was found to affect the spectral signature of the sorbed SA molecule that points to the shift of tautomeric equilibrium between the enol and keto forms. Small size cations, such as H+ and Li+, stabilize a cis-keto SA tautomer along with a enol one in the zeolite structure. The calculations indicate that the sorbed cis-keto tautomer may have the dipole large enough to be considered as a zwitterion. New features appearing in the spectra with the increase of the cation size were attributed to the presence of trans-keto SA tautomer, which up to now has been observed only in time-resolved spectroscopic experiments. A strong interaction of the molecule with cations in Zn-ZSM-5 zeolite results in the chelation of enol SA with the divalent Zn2+ ions. The results of the study suggest that the tautomeric equilibrium of molecules belonging to the Schiff base family can be tuned by the confinement in the nanoporous materials via a choice of topology of zeolite framework and the nature of extra-framework cations.

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“…The C=N stretching vibration of the azomethine group results in an intensive band at 1660--1500 cm -1 region of the IR spectra of the Schiff bases. 2,5,6,8,18,19,27,[29][30][31][32][33][34][35] The symmetrical stretching modes of C6=N2 and C10=N4 bonds cause an intensive band at 1628 and 1650 cm -1 in the IR spectra of the free H 2 A and H 2 B Schiff bases, respectively. Due to coordination of the N2 and N4 azomethine nitrogens to V 4+ , electron density of the C6=N2 and C10=N4 bonds is decreased.…”

Section: Geometry Optimizationmentioning

confidence: 99%

Oxovanadium(IV) complexes of the pyridoxal Schiff bases: Synthesis, experimental and theoretical characterizations, QTAIM analysis and antioxidant activity

et al. 2020

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Two vanadyl complexes of the pyridoxal Schiff bases have been newly synthesized and characterized by several experimental methods, where the 4,4′-[1,4-butanediylbis-[(E)-nitrilomethylidyne])bis[5-hydroxy-6-methyl-3-pyridinemethanol] and trans-4,4′-[1,2-cyclohexanediylbis-[(E)-nitrilo-methylidyne]]bis[5-hydroxy-6-methyl-3-pyridinemethanol] Schiff base were used. Geometry optimization, assignment of the IR vibrational frequencies and the natural bond orbital (NBO) analysis of the complexes have been calculated by employing the density functional theory (DFT) approaches. Deprotonated form of the Schiff bases (L 2-) acts as a tetradentate N 2 O 2 ligand, which coordinates to the V(IV) via two phenolate oxygens and two imine nitrogens. In the square-pyramidal geometry of the [VO(L)], the apical position is occupied by an oxo ligand. The DFT-calculated vibrational frequencies show a good consistency with the corresponding experimental values, confirming suitability of the optimized geometries for the complexes. Characteristics of the bonding interactions have been explored using the quantum theory of atoms in molecule (QTAIM) analysis. The complex formation results in decrease in strength of the C-N bond of the azomethine group and increase in the strength of the CO bonds of the phenolate group. High-energy gaps approve stability of the complexes. Both of the complexes show significant radical scavenging activities against the ABTS and DPPH radicals, even higher than the BHA.

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Intramolecular hydrogen bonding in N-salicylideneaniline: FT-IR spectrum and quantum chemical calculations

Cited by 27 publications

References 87 publications

NH-form of a threonine-based Schiff base in the solid state

NH-form of a threonine-based Schiff base in the solid state

A Spectroscopic Study of Tautomeric Equilibrium of Salicylideneaniline in ZSM-5 Zeolites

Oxovanadium(IV) complexes of the pyridoxal Schiff bases: Synthesis, experimental and theoretical characterizations, QTAIM analysis and antioxidant activity

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