Versatile control of the optical bandgap in heterobimetallic polymers through complexation of bithiazole-containing polyplatinynes with ReCl(CO)5

A new class of soluble, solution-processable heterobimetallic platinum(II)-acetylide polymers functionalized with some rhenium(I)-bithiazole based spacers and their corresponding model complexes were synthesized and characterized. The photophysical (absorption and emission spectra), thermal and electrochemical properties of the polymers were investigated in detail. These mixed-metal PtRe polymers exhibited good thermal stability and strong low-energy broad absorption bands in the visible region. The effects of metal complexation of the bithiazole group with ReCl(CO)5 as well as adding thiophene ring along the polymer backbone on the optical bandgaps of these organometallic polymers were examined. The bandgaps of these polymers were found to be controllable readily by chemical means and can be lowered from 2.18 to 1.89 eV as the number of thiophene ring was increased from 0 to 2. Upon coordination with Re(CO)3Cl moiety, the optical gap of the polymer can be reduced by as large as 0.25 eV.

Heterobimetallic-acetylide polymers consisting of both platinum(II) and rhenium(I) units spaced by a bithiazole chromophore (P0-Re to P2-Re) were synthesized and characterized. The electron-withdrawing rhenium-bithiazole moiety is effective to cause a red-shift of the absorption band relative to the non-rhenium congeners P0–P2, resulting in a polymer with the lowest bandgap of 1.85 eV for P2-Re.Figure optionsDownload as PowerPoint slideHighlights
► Heterobimetallic platinum-acetylide polymers based on rhenium-bithiazole moiety and their corresponding model complexes.
► The photophysical, thermal and electrochemical properties of the polymers.
► The effect of adding thiophene ring and metal complexation on the optical bandgap.