Synthesis and Photophysical Properties of New α,Ω-Bis(Tpy)Oligothiophenes and Their Metallo-Supramolecular Polymers With Zn²⁺Ion Couplers

Five new α,ω-bis(tpy)bithiophenes and terthiophenes, each comprising two hexyl groups attached to oligothiophene block at different positions, were prepared using the Suzuki coupling strategy, characterized (NMR, IR, Raman, HRMS, UV/vis, fluorescence, cyclic voltammetry) and transformed to corresponding conjugated metallo-supramolecular polymers with Zn2+ ion-couplers. Reference oligomers with unsubstituted central blocks and their polymers are also reported. Photophysical properties of oligomers and polymers are described, analyzed with a help of DFT calculations, and correlated with the chemical constitution of oligomeric building blocks. Steric effects were shown to exceed the electronic effects of hexyl groups, and twisting the thiophene-thiophene bonds were shown to influence electronic spectra of oligomers and polymer more deeply than twisting the thiophene-tpy bonds. Outlying photoluminescence characteristics observed for some oligomers and polymers were shown to be consistent with the other data based on their analysis by the Stokes shift approach. Polymers prepared exhibited good constitutional dynamics in DMSO but only limited dynamics in THF solutions. IR and Raman spectra allowing identification of solid oligomers and polymers are also presented.