A facile and efficient approach to synthesize tetra-oligothiophene-substituted calixarenes, Calix-OT(n) with n up to 4 using palladium-catalyzed Kumada coupling of thienylmagnesium bromide and bromo-substituted calixarene as a key step has been developed. The close proximity of the tetra-oligothiophenes constructed within a calixarene assembly leads to peak/band broadening, spectral shifting, i.e., blue-shift in absorption and red-shift in emission spectra as well as fluorescence quantum yield quenching as compared to those of monomers indicating the existence of chromophoric interaction. We have shown that the intra-chromophoric interaction lowers the first ionization (raises HOMO level) of an oligothiophene within an assembly. It also stabilizes the formation of a radical cation, which results in an increase in the subsequent voltammetric oxidation and the occurrence of the higher oxidation states as compared to the monomeric counterparts. This assembly can serve as a model for the investigation of molecular interaction of π-conjugated systems.
Scopus Subject Areas
- Drug Discovery
- Organic Chemistry
- Intra-chromophoric interaction
- Kumada coupling
- Tetra-oligothiophene-substituted calixarene