Mixed‐Functionalized Acylgermanes Result in Wavelength‐Controlled Fragmentation

Abstract

ABSTRACT Control over the radicals that a Type I photoinitiator releases without changing the formulation offers a direct handle on polymer microstructure. To address this challenge, molecular architectures with tailored solubility and reactivity are required. Consequently, we synthesized novel polyethylene glycol (PEG)‐functionalized acylgermanes via a straightforward one‐pot synthetic protocol in good yields, as confirmed by NMR spectroscopy, X‐ray crystallography and UV/Vis spectroscopy. By integrating PEG‐functionalized para ‐alkoxybenzoyl substituents two different aryl‐carbonyl chromophores were introduced. UV/Vis spectroscopy and TD‐DFT (CAM‐B3LYP/def2‐TZVP) analysis assigned complementary bands to the mesitoyl and para ‐alkoxybenzoyl units enabling wavelength‐selective excitation. Photo‐CIDNP tracked the fate of primary Ge/benzoyl radical pairs in the presence of a monomer quencher (butyl acrylate) and revealed competition between two alternative α‐cleavages via CIDNP polarizations of diagnostic aldehydes. By shifting the irradiation window, the balance between mesitoyl‐ and para ‐alkoxybenzoyl‐derived radicals can be systematically tuned, an effect corroborated by steady‐state LED irradiation NMR experiments. Extension of this concept to other mixed tetraacylgermanes demonstrates that wavelength‐selective fragmentation is a general design principle rather than a compound‐specific anomaly. These PEG‐acylgermanes combine polar media compatibility with light‐programmable radical generation, converting small adjustments in wavelength into mechanistic control during photopolymerization.