Clicking acylgermanes: modular access to photoinitiators for visible-light photopolymerization

Abstract

Herein, we report a modular and biocompatible platform of Cu-catalyzed azide–alkyne cycloaddition (CuAAC)-compatible acylgermanes. Broad functional-group tolerance is demonstrated by a library of novel derivatives that were isolated and characterized by NMR, UV/Vis spectroscopy, and mass spectrometry, with selected structures confirmed by single-crystal X-ray diffraction. We also disclose the first acylgermanes bearing unprotected carbohydrate motifs, whose marked polarity enabled initial biological assessment. Representative examples showed low cytotoxicity and measurable affinity for lipid bilayers in assays with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) large unilamellar vesicles. Photo-DSC and photo-CIDNP experiments confirmed efficient photoinitiation and radical pathways characteristic of this class. Coupling acylgermane chemistry with robust CuAAC click methodology expands the scope of acylgermane photoinitiators, enabling rapid late-stage functionalization with diverse motifs and opening routes to complex materials and entry into biological applications.