Infrared and ultraviolet investigation of the conformation and proton acceptor ability of 2,2′-pyridil

Migchels, P.; Maes, Guido; Zeegers‐Huyskens, Th.; Роспенк, М.

doi:10.1016/0022-2860(89)80135-8

Cited by 13 publications

(6 citation statements)

References 14 publications

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“…The first fact to note is that, with a single exception (discussed in detail below), in all these compounds the two halves of the molecule tend to have a maximum number of atoms of the substituent bonded to the carbonyl carbon in the plane of the carbonyl group. 7,8,11,12,19,21,31,32 This trend results from the attempt to maximize resonance (or hyperconjugation, in the case of the methyl substituent) between the carbonyl group and the substituent. On the other hand, in this kind of molecules the conjugation at the intercarbonyl bond has been found to be minimal, [7][8][9][10][11][12] which in fact justifies the great conformational flexibility associated with this bond.…”

Section: Dft(b3lyp)/6-311++g(dp) Calculationsmentioning

confidence: 99%

“…5,6,[8][9][10][11][12][13][14][15][16][17][18] In a-furil, the maximum of the n-p* band position was found to occur at about 425 nm (in cyclohexane solution), compared with 355 and 385 nm for benzil and a-pyridil, respectively. 18 According to the expected correlation between the maximum absorption frequency and the OQC-CQO intercarbonyl dihedral angle, [17][18][19] this observation indicates that a-furil exists preferentially in a conformation exhibiting a more transoid-like dicarbonyl moiety than both benzil and a-pyridil, which have intercarbonyl dihedral angles of ca. 100 and 1201, respectively.…”

Section: Introductionmentioning

confidence: 97%

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Matrix isolation and low temperature solid state FTIR spectroscopic study of α-furil

Lopes

Gómez‐Zavaglia

Fausto

2006

Phys. Chem. Chem. Phys.

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Alpha-furil [C(4)H(3)O-C(=O)-C(=O)-C(4)H(3)O] has been isolated in argon and xenon matrices and studied by FTIR spectroscopy, supported by DFT(B3LYP)/6-311++G(d,p) calculations. The obtained spectra were fully assigned and revealed the presence in the matrices of three different conformers, all of them exhibiting skewed conformations around the intercarbonyl bond with the two C(4)H(3)O-C(=O) fragments nearly planar. The three conformers differ in the orientation of the furan rings relative to the carbonyl groups: the most stable conformer, I (C(2) symmetry; O=C-C=O intercarbonyl dihedral equal to 153.1 degrees), has both furan rings orientated in such a way that one of their beta-hydrogen atoms approaches the oxygen atom of the most distant carbonyl group, forming two H-C=C-C-C=O six-membered rings; the second most stable conformer, II (C(1) symmetry; O=C-C=O intercarbonyl dihedral equal to 126.9 degrees ), has one furan ring orientated as in I, while the second furan group is rotated by ca. 180 degrees (resulting in an energetically less favourable H-C=C-C=O five-membered ring); in the third conformer, III (C(2) symmetry; O=C-C=O dihedral equal to 106.2 degrees ), both furan rings assume the latter orientation relative to the dicarbonyl group. The theoretical calculations predicted the two higher energy forms being 5.85 and 6.22 kJ mol(-1) higher in energy than the most stable form, respectively, and energy barriers for conformational interconversion higher than 40 kJ mol(-1). These barriers are high enough to prevent observation of conformational isomerization for the matrix isolated compound. The three possible conformers of alpha-furil were also found to be present in CCl(4) solution, as well as in a low temperature neat amorphous phase of the compound prepared from fast condensation of its vapour onto a suitable 10 K cooled substrate. On the other hand, in agreement with the available X-ray data [S. C. Biswas, S. Ray and A. Podder, Chem. Phys. Lett., 1987, 134, 541], the IR spectra obtained for the neat low temperature crystalline state reveals that, in this phase, alpha-furil exists uniquely in its most stable conformational state, I.

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Section: Dft(b3lyp)/6-311++g(dp) Calculationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Matrix isolation and low temperature solid state FTIR spectroscopic study of α-furil

Lopes

Gómez‐Zavaglia

Fausto

2006

Phys. Chem. Chem. Phys.

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“…The conjugation of the carbonyl groups with the pyridyl rings would favor the planar molecular configurations in order to achieve maximum overlap, but the steric repulsions between the carbonyl oxygens, between these atoms and the nearest hydrogen atoms of the pyridyl rings and between the two pyridyl substituents preferably twist the whole molecule, making skewed structures to be more stable than the planar ones in the electronic ground state. Investigations carried out for the compound in different solutions [28,33,40] indicated that in these media the compound exists in a single conformation similar to that observed in the crystal, with the intercarbonyl angle decreasing with the increase in polarity of the solvent [33]. On the other hand, according to time-resolved transient absorption spectra measurements, the lowest energy triplet state of ␣-pyridil seems to be planar in non-polar solvents [41].…”

Section: Introductionmentioning

confidence: 99%

“…␣-Pyridil was also studied in the past by FT-IR, Raman, NMR and UV spectroscopies in the solid state and in solution either in the ground or in the excited states [28][29][30][31][32][33][34][35][36][37][38][39][40]. Some of these studies addressed the question of the conformational preferences of this molecule [28,[33][34][35][36][37][38][39][40].…”

Section: Introductionmentioning

confidence: 99%

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Low temperature IR spectroscopy and photochemistry of matrix-isolated α-pyridil

Lopes

Gómez‐Zavaglia

Fausto

2008

Journal of Photochemistry and Photobiology A: Chemistry

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2 ] has been isolated in low temperature argon and xenon matrices and studied by FTIR spectroscopy, supported by DFT(B3LYP)/6-311++G(d,p) calculations. Calculations predicted the existence of three different conformers exhibiting skewed conformations around the intercarbonyl bond and the two C 5 H 4 N C( O) fragments nearly planar. The two higher energy forms, TCG and CCSk were estimated theoretically to be, respectively, 21.0 and 35.1 kJ mol −1 higher in energy than the most stable form, TTG. In consonance with the relatively high energies predicted by the calculations for the two less stable conformers of ␣-pyridil, only the most stable conformer was found spectroscopically to be present in the studied matrices. Infrared spectra obtained for the neat low temperature amorphous and crystalline states reveals that the TTG conformer is also the sole conformer present in these phases. UV irradiation ( > 235 nm) of matrix-isolated ␣-pyridil led to its isomerization into unusual molecular species bearing Hückel-type pyridine (aza-benzvalene) rings.

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Hydrogen‐Bonded Complexes of Phenols

Laurence

Berthelot

Graton

2009

Patai's Chemistry of Functional Groups

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Introduction Hydrogen‐Bond Basicity of Phenols Hydrogen‐Bond Acidity of Phenols Self‐Association of Phenols Intramolecular Hydrogen Bonds Properties of the Complexes Construction of Hydrogen‐Bond Basicity Scalesfrom Phenols Hydrogen Bonding and Protonation

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Infrared and ultraviolet investigation of the conformation and proton acceptor ability of 2,2′-pyridil

Cited by 13 publications

References 14 publications

Matrix isolation and low temperature solid state FTIR spectroscopic study of α-furil

Matrix isolation and low temperature solid state FTIR spectroscopic study of α-furil

Low temperature IR spectroscopy and photochemistry of matrix-isolated α-pyridil

Hydrogen‐Bonded Complexes of Phenols

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