LAUSR

Five para-substituted monoacyltrimethylgermane derivatives, i.e., p-fluorobenzoyltrimethylgermane (pFBG, λmax = 405 nm), p-methoxybenzoyltrimethylgermane (pMBG, λmax = 397 nm), benzoyltrimethylgermane (pHBG, λmax = 409 nm), p-cyanobenzoyltrimethylgermane (pCBG, λmax = 425 nm), and p-nitrobenzoyltrimethylgermane (pNBG, λmax = 429 nm) are investigated via a combination of pulsed laser polymerization with subsequent electrospray ionization and mass spectrometry (PLP-ESI-MS) as well as femtosecond transient absorption spectroscopy. The relative initiation efficiencies of the initiating benzoyl radical fragments of pFBG, pMBG, and pHBG are determined using PLP-ESI-MS. The para-substituted derivatives with the electron-donating groups, pFBG and pMBG, display a factor 1.5 and 1.3, respectively, superior overall initiation efficiency compared to the unsubstituted pHBG. In contrast, the derivatives pCBG and pNBG carrying electron-withdrawing groups display only weak initiation behavior at a factor 4 higher total e...