The core structure of PEGylated NHC precursors were obtained by an alkylation procedure reported by Jadhav et al. using 1methylimidazol with terminally brominated PEG species (av. Mn ~2000 g/mol; for synthesis and characterization of PEG1, methoxy and PEG2, with -azide; refer to Figure and), yielding imidazolium bromides 1 (with PEG1 wingtip) and 2 (with PEG2 wingtip), respectively. Purified compounds were characterized by multinuclear nuclear magnetic resonance (NMR), Fouriertransformed infrared spectroscopy (FT-IR) and matrix-assisted laser desorption/ionization (Maldi-TOF). The results are in accordance with literature findings and confirmed the successful synthesis of 1 and azide-containing 2 without decomposition of the PEG chain and -terminal azide group. Imidazolium bromides (IMZ•Br) 1 and 2 were dissolved in methanol (MeOH) and potassium bicarbonate (KHCO3) was added. Stirring at 35 °C yielded the respective masked NHC precursors 1'and 2' as a mix of PEGylated IMZ•HCO3 and corresponding NHC-CO2 adduct at a ratio of ~3:2 based on integration of the 1 H-NMR spectrum (in d6-DMSO, see ESI for details, Figure ). The observed ratios are in accordance with previously published NMR data. The identification of masked NHC precursors via NMR, as well as the presence of additional HCO3 -/CO2 signals in the region of 1680-1620 cm -1 in the FT-IR spectra, further proves the successful synthesis of the precursors (see ESI for spectra, Figure ). Further, the integrity of the PEG chain was confirmed by Maldi-TOF (see ESI for spectra, Figure ). In parallel, imidazolium bromides were converted via transmetallation using silver(I) oxide (Ag2O) and chloro(dimethyl sulfide)gold(I) ([Au(DMS)Cl]) into the NHC-Au(I) complexes 1-Au (with terminal -OMe) and 2-Au (with terminal -N3) as precursors for the synthesis of PEG-NHC@AuNPs through a bottom-up approach. NHC gold complexes were obtained as a mixture of PEGylated NHC-Au(I) and NHC-Au(III) complexes, as previously reported by Johnson and coworkers, without any decomposition of the PEG chain nor loss of the -azide moiety in case of 2-Au.