Tetraalkoxyphenanthrene-Fused Hexadecadehydro[20]- and Tetracosadehydro[30]annulenes: Syntheses, Aromaticity/Antiaromaticity, Electronic Properties, and Self-Assembly.

Tetraalkoxyphenanthrene-fused hexadecadehydro[20]- and tetracosadehydro[30]annulenes possessing octatetrayne linkages were synthesized and their properties together with those of phenanthrene-fused octadehydro[12]- and dodecadehydro[18]annulenes have been investigated. Various spectroscopic and electrochemical measurements as well as quantum chemical calculations support that planar [20]- and [30]annulenes are weakly antiaromatic and nonaromatic, respectively. The detailed concentration- and temperature-dependent 1H NMR and UV-vis data of present dehydroannulenes provided evidence for the enhancement of π-π stacking interactions by extension of the acetylenic linkages. Dehydroannulenes formed self-assembled clusters and their morphology and crystallinity proved to depend on the length of acetylenic linkages, the shape of dehydroannulene core, and the bulkiness of alkoxy groups appended to the phenanthrene moieties.