Facile, versatile prepolymerization and postpolymerization functionalization approaches for well-defined fluorescent conjugated fluorene-based glycopolymers

We have developed facile, versatile prepolymerization and postpolymerization functionalization approaches to prepare well-defined fluorescent conjugated fluorene-based glycopolymers (polymers A and B) through thioether formation. Well-defined glucose-carrying monomer (5) and conjugated polymer (polymer 2) were prepared by coupling the key precursors, 2,7-diiodo-9,9-bis(6′-bromohexyl)fluorene (2) and poly[(9,9-bis(6′-bromohexyl)-2,7-fluorenylene)-alt-1,4-phenylene] (polymer 1) with an excess of 1-thio-β-D-glucose tetraacetate (3) in a basic condition, respectively. A well-defined poly(2,7-fluorenylene-ethynylene)-alt-1,4-(2,5-dimethy-oxyphenylene-ethynylene) bearing peracetylated glucose residues (polymer 3) was prepared by a palladiumcatalyzed Sonogashira coupling polymerization of monomer 5 with a diethynylbenzene in the presence of 5% CuI, 5% Pd(PPh 3) 2Cl 2 and 10% PPh 3. Polymers 2 and 3 were deacetylated under Zemplén conditions in methanol and methylene chloride containing sodium methoxide, affording two fluorene-based conjugated glycopolymers A and B, respectively. Polymer A was also obtained by the reaction of polymer 1 with 1-thio-β-D-glucose sodium salt hydrate (4) in a basic condition. The composition and purity of the products were reliably analyzed by 1H NMR. Water-soluble fluorene-based conjugated copolymer bearing glucose pendants with tri(ethylene glycol) tethers (polymer C) was prepared by the postpolymerization functionalization approach. This thioether formation reaction offers a very effective conjugation method to covalently attach protected or unprotected carbohydrate residues to fluorescent conjugated polymers. © 2006 American Chemical Society