Diphenyloligothiophene-based dichromophoric macrocycles and their ability to form donor/acceptor complexes

A series of four dichromophoric rigid macrocycles 6a−6d, two with diphenyloligothiophene chromophores, the other two with more electron-rich diphenyl-EDOT or diphenyl-bis-EDOT chromophores, have been synthesized. The absorption spectrum of the diphenyl-bis-EDOT based macrocycle 6d displayed the most pronounced vibronic resolution with a well-resolved 0−0 transition, indicating a fully planarized geometry of the diphenyl-bis-EDOT chromophores. The 1H NMR spectra of the macrocycles displayed weak to moderate chemical shifts of characteristic signals upon addition of π-conjugated oligonitro-9-fluorenone acceptors. X-ray single-crystal analysis showed that columnar π-stacked donor/acceptor complexes are formed with the stacks composed of alternating donor and acceptor molecules. The stoichiometry of the crystalline, dark-colored complexes was found to be 1:1 by elemental analysis and integration of the 1H NMR peaks. The complex formation is accompanied by remarkably large Stern−Volmer constants of fluorescenc...