Synthesis, Chiroptical, and Redox Properties of Ferrocene-Containing Optically Active Polymers

The Sonogashira-Hagihara coupling polymerization of ferrocene-containing l-phenylalanine-derived optically active o-, m-, p-substituted bis(iodophenylene) monomers 1o, 1m, 1p with 1,4-diethynylbenzene (2) and 1,4-diethynyl-2,5-bis[2-(2-methoxyethoxy)ethoxy]benzene (3) is carried out to obtain the corresponding polymers consisting of ferrocene, amino acid, and phenyleneethynylene moieties. In the solution state, poly(1o-2), poly(1o-3), and poly(1m-2) exhibit no circular dichroism (CD) signals in N,N-dimethylformamide (DMF), while poly(1m-3), poly(1p-2), and poly(1p-3) exhibit CD signals assignable to the main chain chromophore, indicating the formation of certain chiral structures. In the solid state, poly(1o-2), poly(1o-3), poly(1m-2), and poly(1m-3) exhibit CD signals in the solid state, while poly(1p-2), poly(1p-3) does not, indicating the different aggregation manners of the polymers in the solution and solid states. The monomer and the polymers exhibit redox properties assignable to the ferrocene moieties. Thermal gravimetry analysis (TGA) measurements reveal that a 30% weight reduction occurs at 500 degrees C yielding black ferromagnetic solids.