Description
The majority of state-of-the art visible light photoinitiators like acylphosphines, acylstannanes and acylgermanes decompose into radical species via Norrish type I reaction (α-cleavage). [1] When short lived radicals are formed, 1H-CIDNP (chemically induced dynamic nuclear polarization) spectra recorded in the presence of a monomer show polarized NMR signals (either enhanced emission or adsorption) and formation of aldehydes. [2] In the case of our studied 1,2-bis(tris(2,4,6-trimethylbenzoyl) germyl)ethane-1,2-dione and hexakis(trimethylsilyl)digermane no polarized signals and no formation of aldehydes was detected. That´s why we decided to study these new germanium photoinitiators with various spectroscopic techniques like IR, UV-vis, EPR spin trapping and NMR to understand their photoreactivity. Our results so far show that the behavior of 1,2-bis(tris(2,4,6-trimethylbenzoyl) germyl)ethane-1,2-dione differs in the presence of blue and green visible light. By the use of 520 nm LED source (green light) we could see the standard α-cleavage-type of reaction forming DMPO-benzoyl radical adducts in the EPR. On the other hand, time-resolved IR spectra have shown that shorter wavelengths like 355 nm LED (blue light) results in a specific rearrangement in the structure – formation of a ketene.| Period | 19 Jun 2024 |
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| Event title | 8th European Symposium of Photopolymer Science: ESPS 2024 |
| Event type | Conference |
| Location | Stresa, ItalyShow on map |
| Degree of Recognition | International |