Tetrabenzo[ab,  f, jk,o][18]annulene: synthesis, crystal structure analysis, ab initio quantum-chemical studies of intermolecular interactions in the gas phase and in crystalline states, photodimerization and photopolymerization

Abstract

The synthesized title compound 8 crystallizes in three different modifications, which were investigated by electron crystallography, high resolution electron microscopy and X-ray structural analysis. The formation of molecular pairs was studied by an ab initio quantum-chemical approach. The calculated "dimers" were compared to the mutual orientations of nearest neighboring molecules in the crystal structures and to covalently bonded dimers obtained by a topochemical photodimerization.

Areno-Condensed Annulenes - Extended Discotic Mesogens

“…The condensation of benzene or higher arene ring systems on the annulene perimeter enhances significantly the thermal stability. In the series of [18]annulene (2), 10 a variety of benzo-condensed compounds has been studied, for example the monobenzo system 3, 11 the dibenzo systems 4 12 and 5, 13 the tetrabenzo system 6a, 14 the hexabenzo system 7, 15 which represents a hexa-m-phenylene, the 'nonabenzo' system 8 16 and the 'dodecabenzo' system 9, 17 wellknown as kekulene ( Figure 2). Apart from the fact, that all these hydrocarbons are disclike compounds with a central 18-membered ring, the chemical character of the compounds is different.…”

Synthesis of Tripyreno[2,3,4-abc: 2,3,4-ghi: 2,3,4-mno][18]annulenes

“…In contrast to the unsubstituted [18]annulene [21], the areno-condensed [18]annulenes are not planar [4,6,11]. They can be regarded as aromatic "islands" which are combined by trans configured olefinic "bridges".…”

“…The data presented below refer to the pure (E)-configuration. 4 Preparation according to the literature [11]. The product was identified by comparison with an authentic sample.…”

“…Moreover, these disc-like systems represent discotic mesogens which are a precondition for the formation of liquid crystals with discotic nematic or columnar phases [6 -11, 13]. The photochemistry of these compounds provides an access to belt cyclophanes [4,5,7,8,13]; the major applications in materials science are in the field of imaging techniques and photoconductivity [9, 10, 13 -15].…”

“…Many areno-condensed annulenes exhibit a high tendency of aggregation in solution as well as in the neat phase [4,6,7,8,11]. Thus, bimolecular photoreactions are efficient even in highly diluted solutions, because light is being absorbed by aggregates (dimers etc.).…”