INTRAMOLECULAR-PROTON TRANSFER, EXPERIMENTAL AND THEORETICAL CHARACTERIZATION OF 3,3c-DIHYDROXY-4,4c-[4,4c-DIPHENYLMETHANEBIS (NITRILOMETHYLIDYNE)]-BIS-PHENOL
A newly synthesized Schiff base 3,3c-dihydroxy-4,4c-[4,4c-diphenylmethanebis(nitrilomethylidyne)]-bis-phenol is characterized experimentally. Also, the geometry optimization for the tautomers, tautomerism and assignment of the IR bands and NMR chemical shifts of the Schiff base were performed using the DFT method. Good consistency between the theoretical and experimental results confirms the validity of the optimized geometry. Geometries of four possible tautomers are fully optimized. None of them has a planar structure, but each of the benzene rings is in a separate plane. In the most stable tautomer L1, the phenolic protons are engaged in the intramolecular-hydrogen bond with the azomethine nitrogen atoms. Tautomerization of L1 can occur in two different pathways which are computationally studied using DFT and the Atoms In Molecules (AIM) analysis. Both pathways have the same barrier energy.
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2015. 56, 5
UDC 541.6:541.67
INTRAMOLECULAR-PROTON TRANSFER, EXPERIMENTAL AND THEORETICAL
CHARACTERIZATION OF 3,3-DIHYDROXY-4,4-[4,4-DIPHENYLMETHANEBIS
(NITRILOMETHYLIDYNE)]-BIS-PHENOL
H. Eshtiagh-Hosseini1, S.A. Beyramabadi2, M. Mirzaei1, A. Morsali2, M.A. Naseri3,
H. Chegini2, M. Elahi2
3Department of Chemistry, Faculty of Science, Birjand University, Birjand, Iran
Received January, 13, 2014
1Department of Chemistry, Ferdowsi University of Mashhad, Mashhad, Iran
2Department of Chemistry, Mashhad branch, Islamic Azad University, Mashhad, Iran
E-mail: beiramabadi6285@mshdiau.ac.ir
Revised — July, 11, 2014
A newly synthesized Schiff base 3,3-dihydroxy-4,4-[4,4-diphenylmethanebis(nitrilomethylidyne)]-bis-phenol
is characterized experimentally. <...> Also, the geometry optimization for the
tautomers, tautomerism and assignment of the IR bands and NMR chemical shifts of the Schiff
base were performed using the DFT method. <...> Geometries of four possible
tautomers are fully optimized. <...> None of them has a planar structure, but each of the benzene
rings is in a separate plane. <...> In the most stable tautomer L1, the phenolic protons are engaged
in the intramolecular-hydrogen bond with the azomethine nitrogen atoms. <...> In continuation of our previous works on the chemistry of Schiff bases [12—18 ], herein we report
the synthesis, experimental and theoretical investigation of a new Schiff-base (3,3-dihydroxy4,4-[4,4-diphenylmethanebis(nitrilomethylidyne)]-bis-phenol),
which is named as L. By comparing
the theoretical and experimental results, the validity of the optimized structures has been evaluated. <...> The optimized geometries were confirmed to
have no imaginary frequency of the Hessian, which was used for the additional calculations, including
the frequencies, NMR chemical shifts, and AIM calculations. <...> The 1H and 13C NMR chemical shifts of
the L species were predicted with respect to tetramethylsilane (TMS). <...> Considering two intramolecular proton transfers, there are four possible
tautomers for the titled Schiff base, geometries of which are optimized in both gas and solution phases. <...> Structure and B3LYP optimized geometry of L1 together with its labeling
904
H. ESHTIAGH-HOSSEINI, S.A. BEYRAMABADI, M. MIRZAEI ET AL. <...> Table 1
Selected structural parameters of
3,3-dihydroxy-4,4-[4,4-diphenylmethanebis(nitrilomethylidyne)]-bis-phenol
Bond length, pm
Angle, deg. <...> The benzene rings <...>
** - вычисляется автоматически, возможны погрешности
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