Conjugated Metallo-Supramolecular Polymers Containing a Phosphole Unit

A new building block, TPT, composed of the substituted phosphole ring surrounded by two thiophene rings with 2,2′:6′,2″-terpyridine-4′-yl (tpy) end-groups, is prepared and assembled with metal ions (Co²⁺, Cu²⁺, Fe²⁺, Ni²⁺, and Zn²⁺) into metallo-supramolecular polymers (MSPs), and properties of both TPT and the MSPs are compared with those of their counterparts with terthiophene central blocks. A distinct red-shifting of the UV/vis band about by 60–100 nm proves the decrease in the bandgap energy due to replacing the thiophene-2,5-diyl with a phosphole-2,5-diyl central unit, which is due to the lowered aromaticity of phosphole ring compared to the aromaticity of thiophene ring. Assembling TPT with metal ions gives oligomeric chains comprising up to 10 unimeric units in dilute solutions. MSPs with Fe²⁺ and Ni²⁺ ion couplers exhibit very slow constitutional dynamics, while those with Cu²⁺ and Zn²⁺ ion couplers quite fast constitutional dynamics. A metal–ligand charge transfer is observed only for Fe²⁺-MSPs, while luminescence is observed only for Zn²⁺-MSPs, mainly at an excess of Zn²⁺ ions, which indicates a positive effect of the end-capping of MSP chains with these ions.