Novel optically active methacrylic polymers containing side-chain porphyrin moieties for chiral recognition

Abstract

Novel optically active methacrylic homopolymers bearing in the side chain one or more chiral groups of one single configuration ( l-lactic acid residue) linked to tetraphenylporphyrin have been successfully synthesized and fully characterized. These intrinsically chiral polymers exhibit remarkable thermal stability, with glass transition temperature in the range 250–315 °C and decomposition temperatures in the range 360–390 °C. Spectroscopic, thermal and chiroptical characterizations indicate the occurrence of dipolar interactions among the side chain moieties and the presence of chiral helix conformation at least for chain segments of the macromolecules. The macromolecular Zinc-porphyrin material resulted capable to bind optically active α,ω-diamine guests through nitrogen/zinc coordination to form complexes exhibiting exciton-coupled bisignate Circular Dichroism (CD) spectra with signs related to the absolute configuration of the guest compound. This behavior is due to the formation of diastereomeric complexes which lead to a preferred porphyrin helicity, at least for chain segments. The method turns out to be very sensitive, requiring only few micrograms of guest compound.