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

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