Symmetric meta-terphenyl derivatives as visible light photosensitizers: Advancing iodonium salt-based 3D printing nanocomposites

This article describes ten symmetric m-terphenyl derivatives with appropriately modified structures. The main structure of each newly synthesized compound is m-terphenyl with the following substituents: 2x nitrile group and diethylamine group. This combination provides electron-acceptor character. Furthermore, the m-terphenyl structure was symmetrically modified with additional electron-donor amine groups. The core modification of m-terphenyl with amino groups achieved the preferred spectroscopic properties as a bathochromic spectral shift compared to the reference terphenyl without additional amino groups. The appropriately designed structure of the new symmetric m-terphenyl derivatives allowed their application as high-performance iodonium salt photosensitizers for initiating radical and cationic photopolymerization utilizing light sources in the visible range. The preferred spectroscopic, thermodynamic, and kinetic properties of the investigated m-terphenyl derivatives encouraged the verification of their suitability for preparing polymer nanocomposites by employing a light-initiated 3D printing technique. In addition, the suitability of m-terphenyl derivatives as photocatalysts for metal-free atom transfer radical polymerization (ATRP) was examined, as a potential future direction.