An x-ray determination of the conformation of dibenzo[b,f]tropone

Tropolone, C7H602, crystallizes in space group P21/e, with a= 7.135, b---12.178, c= 7.122 A, fl= 99.63 ° and Z= 4. The crystal structure was solved by the symbolic addition procedure and refined by the leastsquares method to give the final R value of 0.054 for the 853 observed reflexions. The molecule is essentially planar and exhibits a slight degree of bond alternation in the seven-membered ring. The hydroxyl group makes a bifurcated hydrogen bond with carbonyl oxygen atoms, of which one branch is intramolecular and the other intermolecular. The latter intermolecular branches form a hydrogenbonded dimer. These characteristic hydrogen bonds seem to play a role in increasing the contribution from the dipolar ionic forms to the ground state of the tropolone molecule.

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“…122. 1,a=7.135+0.004,b=12.178+ 0"005,c=7.122+0.007 A, fl=99.63+0"05 °. Absent spectra, 0k0 when k is odd and hOl when l is odd.…”

Section: Methodsmentioning

confidence: 99%

The crystal and molecular structure of tropolone

Shimanouchi¹,

Sasada²

1973

Acta Crystallogr Sect B

101

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“…Quant au DCHO lui-m~me, s'il est vrai qu'il avait pr6c6demment fait l'objet d'une d&ermination de structure (Shimanouchi, Hata & Sasada, 1968) ses coordinat~es fractionnaires n'avaient pas &~ publi6es. Celles-ci &ant indispensables h la param~trisation des donn6es en vue d'une confrontation de d6riv6s voisins, nous avons 6t6 conduits fl d&erminer et publier la structure compl&e de ce tricyclique.…”

Section: Introduction Dans Le Cadre D'un Programme D'andudesunclassified

“…Comme pour tous les tricycliques apparent,s [et notamment l'iminostilb~ne (Reboul, Cristau, Soyfer & Estienne (1980), le DDCH (Reboul, Cristau & P~pe, 1981) et le DDCHO (Reboul, Soyfer, Cristau, Darbon, Oddon & P~pe, 1983)] les deux cycles du DCHO ne sont pas coplanaires. Leur angle de pliage [142,8(6) °] (en accord avec celui publi~ par Shimanouchi et al, 1968) [--140,9 (4) °dans le DDCHO pour -140,1 (9) °dans le DCHO]. (2) 6185 (8) 5937 (29) 7795 (14) 4,8 (6) C (3) 6018 (9) 5051 (29) 8510 (15) 5,2 (7) C (4) 5374 (7) 3364 (27) 7939 (12) 4,3 (5) C (5) 4179 (7) 980 (26) 6125 (13) 3,8 (5) C (6) 3525 (7) 994 (25) 4925 (14) 3,9 (5) C (7) 2536 (7) 3242 (26) 2759 (14) 4,9 (6) C (8) 2263 (8) 4653 (30) 1643 (15) 5,5 (7) C (9) 2734 (8) 5434 (29) 1464 (13) 5,0 (6) C (10) 3477 (8) 4692 (26) 2452 (13) 4,5 (5) C(I 1) 3764 (7) 3338 (22) 3597 (14) 3,4 (4) C (12) 3297 (7) 2564 (23) 3795 (12) 3,8 (4) C (13) 4865 …”

Section: Introduction Dans Le Cadre D'un Programme D'andudesunclassified

Structure du 5H-dibenzo[a,d]cycloheptènone-5, C15H10O. Support tricyclique de médicaments psychotropes

Oddon¹,

Darbon²,

Reboul³

et al. 1984

Acta Crystallogr C

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“…DBT is non-planar in the unconstrained form [7], which causes bands E, F and H to appear as doublets. Their conversion to singlets on adsorption of DBT by clays suggests that the molecule assumes an approximately planar configuration in the clay i nterlayers.…”

Section: Electronic Spectramentioning

confidence: 99%

Effect of temperature on the conformation of dibenzotropone adsorbed on montmorillonites

Grauer

Yariv

Heller-Kallai

et al. 1983

Journal of Thermal Analysis

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The nature of the adsorption complex formed between dibenzotropone (OBT) and montmorillonite at elevated temperatures is strongly dependent on the interlayer cations. This was shown by electronic and IR spectra, by X-ray diffraction, and by study of the effects of gradual heating of the samples on these analyses. All samples exhibited significant red shifts of the electronic spectra of DBT into the visible range. These red shifts are attributed to two factors, both contributing to the enhancement of the tropylium planar character of DBT: hydrogen-bonding of acidic interlayer water to the carbonyl group, imparting positive charge to the tropone ring; and ~r interactions between the aromatic moiety and the oxygen planes. The position of the maximum was temperature-dependent for Cu-, Ni-, AI-and Fe-montmorillonites, for which heating (100 ~ under vacuum increased the red shift. The organic molecule assumes a planar conformation and is oriented parallel to the clay layers. IR spectra confirming this conformational orientation of DBT are discussed.The basal spacings of the DBT montmorillonite associations depend on the number of water and DBT sheets present in the interlayers. Layers with one or two sheets of DBT and with up to two sheets of water could be distinguished, leading to a maximum spacing of 20.4 ~.Adsorbent-adsorbate interactions induce spectral changes as compared to solution measurements [1, 2]. These spectral changes, which may include shifts in adsorption bands, changes in extinction coefficients, changes in band shape and the appearance or disappearance of bands, are a direct result of (a) the non-symmetry of the adsorbate environment as compared to a symmetrical solvation shell, resulting in adsorbate conformational changes and (b) chemical and physical irregularities and inhomogeneities of the surface, giving rise to special adsorbate-surroundings interactions not usually found in solution [3].Adsorption of organic cationic dyes by montmorillonite generally causes distinct shifts of the absorption maxima in the visible spectrum (metachromasy). Bergmann and O'Konski [4] attributed such shifts to dye-dye interactions on the surface of montmorillonite, a reaction similar to the aggregation of dye molecules in aqueous solutions. In these dye clusters ~ interactions between parallel aromatic moieties result in shifts in the electronic spectrum. Yariv and Lurie [5] showed, however, that spectra! shifts also occur with dye-montmorillonite complexes in which only mono-

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An x-ray determination of the conformation of dibenzo[b,f]tropone

Cited by 19 publications

References 5 publications

The crystal and molecular structure of tropolone

The crystal and molecular structure of tropolone

Structure du 5H-dibenzo[a,d]cycloheptènone-5, C15H10O. Support tricyclique de médicaments psychotropes

Effect of temperature on the conformation of dibenzotropone adsorbed on montmorillonites

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