Crystal structure anthracenes

Our understanding of the importance of steric factors was initiated by structure determinations by X-ray diffraction techniques of two trans-diols of benz[a]anthracene (89), XVI and XVII, shown in Figure 12. The crystal structures showed diequatorial... 

At —30°C in THF, in the presence of anthracene a single-electron transfer from 118 to anthracene occurs, with the formation of insoluble (Ci4Hio)2Mg(THF)6 (equation 12) . A further reaction with MgCl2 affords the radical anion complex [Mg2Cl3(THF)6] [CiaHio] " (119). An X-ray crystal-structure determination of 119 clearly shows the presence of anthracene radical anions as distinct species in the crystal lattice (Figure 58) . The bond lengths and the deformation of the electron density of the anthracene radical anion clearly show that in 119 the LUMO is occupied by one electron . 

For instance, head-head photodimers are predicted from the crystal structures of 9-cyanoanthracene and 9-anthraldehyde, but the head-tail isomer is produced. Craig and Sarti-Fantoni and later others found that photoreactions of 9-cyanoanthracene and 9-anthraldehyde take place at defect sites [96,215], Systematic photochemical and crystallographic studies by Schmidt and co-workers uncovered many cases of substituted anthracenes which behave in an unexpected fashion (Scheme 40) [216,217]. Examples shown in Scheme 40 clearly illustrate that, unlike cinnamic acid derivatives, the stereochemistry of the product dimer from anthracenes cannot be predicted on the basis of crystal packing. An example from the laboratories of Venkatesan is noteworthy in this context [218], Irradiation of crystals of 7-... 

Occasionally, long-range disorder and/or different phases may coexist within a crystalline material. Arrangement of molecules in the different regions will necessarily be different in at least some respects. One of the earliest reports of invocation of this phenomenon involves the photodimerization of anthracene in the crystalline state [219]. In the crystal structure of anthracene, the faces of no molecules are separated by <4 A. Yet upon irradiation, a dimer is readily formed. Thomas, Jones, and co-workers used electron microscopy to reveal the coexistence inside normal anthracene crystals of regions of a metastable phase. In the minor phase (space group PI), the C9- -C9. distance is 4.2 A, whereas in the stable crystal it is 4.5 A. The dimerization is proposed to originate in the minor phase of the crystal. 

The molecular geometry of the parent cis-1,2-di-9-anthrylethylene 38a has not been established by X-ray diffraction, but crystal structure analyses of several 1,2-substituted cis-dianthrylethylenes 38 are available. Depending on the spatial demand of the substituents R and R, the planes of the anthracene moieties are twisted out of the plane of the ethylene by 59-84° [80],... 

The crystal structure of benzene itself is even more difficult, and it is only quite recently that accurate results have been obtained. The early work on naphthalene and anthracene was also inconclusive and did not at first lend any support to the idea of strictly planar molecules. The first really conclusive results were obtained for the molecule of hexamethylbenzene (Lonsdale, 1929). In the triclinic crystal structure the atoms occupy general positions, but a careful study of the intensities of the reflections, particularly those from the pronounced cleavage plane in which the molecule is found to lie, established that the molecule was planar to within narrow limits, and also that the benzene ring was a regular hexagon. Soon afterwards the more difficult structures of naphthalene and anthracene were fully analysed with the aid of absolute intensity measurements and the use of Fourier methods of analysis (Robertson, 1933a), and it was shown that the atoms were coplanar to within a few hundredths of an Angstrom unit. 

The crystal structures of a series of anthracene derivatives (9-nitro- and 9,10-dinitro-anthracene, 9,10-dichloro- and 9,10-dibromo-anthracene, and 9-anthraldehyde) have been investigated by Trotter (1958a, 1959a, b). In 9-anthraldehyde (65) significant out-of-plane... 

Preliminary X-ray investigations of crystals of 9,10-dihydro-anthracene (66) (Iball, 1938) showed that the most likely space group was P2X which, with two molecules in the unit cell, gave no indication of the molecular symmetry. A non-planar conformation for 9,10-dihydroanthracene has been established by Ferrier and Iball (1954). Their crystal structure analysis, using two-dimensional Fourier methods, shows clearly that the molecule is not planar but is bent about the line joining the carbon atoms 9 and 10. Each half of the molecule appears to be planar, the two halves being inclined to each other at approximately 145°. 

Figure 8.71 Skeletal representations of face-to-face stacking in the X-ray crystal structures of some typical charge transfer complex co-crystals (a) naphthalene-TCNE, (b) skatole-trinitrobenzene, (c) perylene-fluoroanil (d) anthracene-trinitrobenzene and (e) TCNQ-TMPD.

To develop a system of linear templates to control the [2 + 2] cycloaddition in the solid state, we turned to crystal structure studies involving a bis(resorcinol) anthracene [19,20]. In particular, it had been shown that co-crystallization of a l,8-bis(resorcinol)anthracene with anthraquinone yielded a one-dimensional (1-D) hydrogen-bonded polymer wherein each resorcinol unit of the anthracene organized, by way of O-H O hydrogen bonds, two quinones in a face-to-face... 

A fluorescent cationic tetranuclear gold(I) rectangle, [(/v-Ph2PAnPPh2)Au2 (//-4,4,-bpy)2Au2(/i.-Ph2PAnr,Ph2)]X4 (X = PF6, NO3), was assembled using 9,10-bis(diphenylphosphino)anthracene and 4,4/-bipyridyl [124]. The molecular rectangle has a cavity of 7.921(3) x 16.76(3) A as reflected from its crystal structure, and its complexation behavior towards various aromatic molecules at the cavity was demonstrated. 

To examine the correlation between crystal structure and triboluminescence we prepared and studied two series of compounds with some brightly triboluminescent members 9-substituted anthracenes (14) (Series I) and alkylammonium tetrakis(dibenzoylmethanato)europates and other lanthanates (Series II). 

Finally, two other types of n coordination to sodium documented by crystal structure data will be mentioned. rc-Type bonding interactions between bis(THF)sodium units and the benzene rings of complex aluminate anions derived from naphthalene or anthracene have been found in the compounds [Na(THF)2]2[Me2AlC10H8]2 and [Na(THF)2]2[Me2AlC14H10]2 (46). Even more complex coordination patterns between sodium, transition metals, and n systems have been reported by Jonas and Kruger (5). 

Topochemically controlled solid reactions are governed by the crystal structure of the solid. Even if the intrinsic reactivity allows for a reaction, the topochemical restrictions circumvent a conversion. The photodimerization of solid anthracene was observed electron microscopically at dislocations [85], The reason for this is the possibility of molecule rotation at the dislocation, and not only the high pressure. 

The crystallization of magnesium anthracene itself proved to be difficult, owing to its low solubility even in THF. Therefore, derivatives with substituents at the anthracene moiety were the first to be structurally characterized. Crystal structures were obtained for [9,10-bis(trimethylsilyl)an-thracene]magnesium (THF)2 (54) (56) and a 1 1 adduct of... 

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