Tuning the optical properties of ethynylene triptycene-based copolymers via oxidation of their alkyne groups into α-diketones

The synthesis of ethynylene triptycene-based copolymers with various aromatic spacers (3a–d) is reported using the palladium-catalyzed Sonogashira cross-coupling reaction. The alkyne groups of 3a–d were oxidized into their respective α-diketone copolymers 4a–d. Formation of 3,4a–d was confirmed by several characterization techniques, such as, gel permeation chromatography (GPC), ¹H and ¹³C nuclear magnetic resonance (NMR), FT-infrared (FTIR), UV–vis absorption, and emission spectroscopies. It was found that the nature of the aromatic spacer influences the emission properties of the target α-diketone triptycene copolymers, causing either a red or blue-shift with respect to that of their ethynylene triptycene copolymer synthons. Copolymers 4a–c with fluorene spacers reveal emission in the range of 440–475 nm, thus, qualifying them to act as blue emitters.