Assembling of bis(tpy)fluorenes with Zn2+ and Fe2+ ions into metallo-supramolecular polymers with highly efficient white-light emission
Abstract
Three fully pi-conjugated bisterpyridines with fluorene unit in the central block were synthetized using the Suzuki-Miyaura coupling and transformed to corresponding conjugated metallo-supramolecular polymers (MSPs) with Zn2+ or Fe2+ ions. Assembling course of MSPs was investigated by absorption and emission spectroscopy, size-exclusion chromatography and viscometric measurements.
Two systems with Zn2+ ions showed white emission with high quantum yields of fluorescence. The constitutional dynamics of Zn-polymers is fast while that of Fe-polymers is as slow that it allows effective separation of the polymer in SEC columns.
Electronic spectra and SEC measurements proved that excess of Fe2+ ions results in their end-capping by these ions and shortening of the polymer chains. The phenomenon of shortening of the polymer chains by surplus of metal ions was additionally confirmed by viscometry measurements for both ion-couplers, which provides us new awareness about the length of MSPs with Zn2+ ions.