Superaromatic terpyridines: hexa-peri-hexabenzocoronenes with tridentate functionality.

Two superaromatic terpyridine ligands (1 and 2) incorporating a hexa-peri-hexabenzocoronene (HBC) unit at the 4'-position have been prepared. In 1, the terpyridine and the HBC domains are directly fused, while in 2, they are separated by an acetylene linker. Also presented is the synthesis and characterization of several novel HBC derivatives, including 2-iodo-5,8,11,14,17-penta-tert-butylhexa-peri-hexabenzocoronene (7), a valuable synthetic intermediate. Different synthetic routes to 1 and 2 are employed, and two alternative methods resulted in excellent yields of 2. The optical properties of both novel terpyridines are examined using UV-visible absorption and emission spectroscopy. The single-crystal X-ray structures of 7 and a precursor, 4-iodo-4'-tert-butylphenylacetylene (5), are discussed.