Two new organoboron quinolate polymers were prepared under exceptionally mild conditions via a novel polycondensation reaction involving boron-induced ether cleavage. The polymers, which contain both the boron and quinolato moieties in the main chain, were characterized by multinuclear and 2D NMR, gel permeation chromatography, and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. They are readily soluble in common organic solvents and thermally stable to <300 °C according to thermogravimetric analysis. The photophysical properties strongly depend on the nature of the conjugated bridge connecting the organoboron quinolato groups. Therefore, with a highly delocalized Th-C 6H 4-Th (Th = thiophene) linker, the lowest energy absorption corresponds to intramolecular charge transfer (ICT) from this conjugated linker to the pyridyl moiety. In contrast, with a less delocalized biphenyl linker, ICT occurs from the fluorene moiety of the diboron monomer to the pyridyl rings on the basis of time-dependent density functional theory (TD-DFT) calculations on molecular model systems. The polymer with the biphenyl linker displays a strong yellow-green emission, whereas the Th-C 6H 4-Th linker shows an unusual concentration-dependent dual emission as a result of excimer formation.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry