Conjugated Metallo-Supramolecular Polymers Containing a Phosphole Unit

Overview & Synopsis

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 shift of the UV/vis band about 60 to 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 of TPT with metal ions gives oligomeric chains comprising up to ten 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 to ligand charge transfer is observed only for Fe2+-MSPs, while luminescence 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