The problem of acoplanarity of aromatic azomethines

Минкин, В. И.; Zhdanov, Yu. A.; Medyantzeva, E.A.; Ostroumov, Yu.A.

doi:10.1016/0040-4020(67)80011-5

Cited by 93 publications

(11 citation statements)

References 32 publications

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“…4a The φ 2 angle was found to be temperature sensitive, e.g., φ 2 ) 39°at 33°C and φ 2 ) 44°a t 35°C. A recent two-dimensional NMR study 4b reported the φ 2 value of 33 (5)°which was comparable with the values of 24°and 43°determined in the previous NMR studies. 4c,d The comparison of the GED value with these NMR data shows that the φ 2 angle slightly increases on going from the nematic phase to the gas phase.…”

Section: Comparison Between Experimental and Theoretical Structuressupporting

confidence: 86%

Gas-Phase Molecular Structure of MBBA (4-Methoxybenzylidene-4‘-n-butylaniline), a Mesogen, by Electron Diffraction Combined with ab Initio Calculations

et al. 1999

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The molecular structure of a typical mesogen, 4-methoxybenzylidene-4′-n-butylaniline (MBBA, CH 3 O-C 6 H 4 -CHdN-C 6 H 4 -(CH 2 ) 3 -CH 3 ), has been studied by gas-phase electron diffraction (GED). The nozzle temperature was about 150°C. Structural constraints in the GED data analysis were obtained by the ab initio MO calculation at the HF/4-21G(*) level of theory. Vibrational amplitudes and shrinkage corrections were calculated from the harmonic force constants given by a normal coordinate analysis. The phenylene ring attached to the C(dN) atom and the azomethine group (-CHdN-) are essentially on the same plane, i.e., the dihedral angle is 0(12)°. The phenylene ring bonded to the nitrogen atom is found to be out of the plane of the azomethine group and the determined value of the dihedral angle, 48(9)°, in the gas phase is larger than that in the crystalline state. This is mainly due to the steric interaction between the hydrogen atoms of the azomethine group and the phenylene ring. In the gas phase the four rotational conformers with respect to the configurations of the n-butyl group were assumed to exist. Their conformational abundance was fixed, as calculated from the ab initio relative energies. The principal bond distances and angles (r g /Å and ∠ R /deg) determined by GED are r(NdC) ) 1.290 (12), r(C-N) ) 1.413 (12), r(C az -C ring ) ) 1.467 (3), 〈r(C ring -C ring )〉 ) 1.400 (6), ∠C-NdC ) 119.0(18), ∠NdC-C ) 121.6(13), ∠NC ring C 14 ) 128.5(25), ∠C az C ring C 4 ) 121.2 (dependent), 〈CCC ring 〉 ) 120.0(3), 〈∠CCC butyl 〉 ) 116.2(11), ∠C 5 C ring O )129.3 (16), where C az , C ring , and C butyl denote the carbon atoms of the azomethine, phenylene and butyl groups, respectively. C 14 and C 4 are the C atoms of the rings synclinal to the C(dN) atom and cis to the H az atom, and C 5 is the C atom of the ring cis to the C atom of the methoxy group. The values in parentheses are three times the standard deviations. The notation 〈 〉 represents the average value. The transition temperature from the nematic to liquid phases was discussed on the basis of the determined molecular structure.

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Section: Comparison Between Experimental and Theoretical Structuressupporting

confidence: 86%

Gas-Phase Molecular Structure of MBBA (4-Methoxybenzylidene-4‘-n-butylaniline), a Mesogen, by Electron Diffraction Combined with ab Initio Calculations

et al. 1999

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“…In the series of benzylideneaniline structures, the various CH=N, CH-C(arom), and N-C(arom) bond lengths generally follow the pattern expected if the first effect is dominant, at least at torsion angles up to about 40 ~ at which point the ~-delocalization energy is still approximately 75% of its value at 0 ~ (Minkin et al, 1967). Although the magnitude of the esd's limits its statistical significance, the pattern of bond lengths in this compound is Consistent with the electronegativity of bromine as a substituent in comparison with other substituents.…”

Section: --Br'mentioning

confidence: 78%

Molecular conformation and electronic structure. II: Crystal and molecular structure ofN-(p-bromobenzylidene)-p-bromoaniline

Bernstein

Izak

1975

Journal of Crystal and Molecular Structure

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The structure of the title compound C13HgBr2N has been determined with MoKcq diffractometer data, and refined by full-matrix least squares to R = 0.06"1 for 888 observed reflections. The crystals are monoclinic: space group P21/a, a = 24.912(13), b = 5.877(1), e = 4.046(1) A, t3 = 92.42(3) ~ Z = 2. The uv absorption spectrum indicates a nonplanar conformation in solution. In the solid, the molecule is disordered about a crystallographic inversion center and is planar to within 0.045 )~.

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“…This lack of coplanarity of the BA molecule is confirmed also in a theoretical way. 28 The calculation have been performed for the (BA), system configurations obtained by the parallel translations of the second molecule with respect to the first one along the z-axis (see Figure 1) and by the subsequent rotations by the angle C#J of this second molecule around the same z-axis.…”

Section: Testing Calculationsmentioning

confidence: 99%

On the Interaction Energy Between Some Nematogenic Molecules

Baran¹,

Leś

1979

Molecular Crystals and Liquid Crystals

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Calculation of the interaction energies between nematogenic MBBA and PAA molecules have been performed in the framework of the Rayleigh-Schrodinger perturbation theory, supplemented with the empirical repulsive term. The predominant role of dispersion interaction as well as negligibly small induction energy have been found. The electrostatic contribution to the interaction energy has been discussed. Some remarks relating to the possible mode of molecular motion have also been made.

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The problem of acoplanarity of aromatic azomethines

Cited by 93 publications

References 32 publications

Gas-Phase Molecular Structure of MBBA (4-Methoxybenzylidene-4‘-n-butylaniline), a Mesogen, by Electron Diffraction Combined with ab Initio Calculations

Gas-Phase Molecular Structure of MBBA (4-Methoxybenzylidene-4‘-n-butylaniline), a Mesogen, by Electron Diffraction Combined with ab Initio Calculations

Molecular conformation and electronic structure. II: Crystal and molecular structure ofN-(p-bromobenzylidene)-p-bromoaniline

On the Interaction Energy Between Some Nematogenic Molecules

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