Ligand Size Distribution of Phenanthroline-Functionalized Polyethylene Glycol-Iron(II) Complexes Determined by Electrospray Ionization Mass Spectrometry and Computer Simulation

The complex formation in solution, and the gas-phase dissociation of a phenanthroline-terminated poly(ethylene glycol) with Fe2+ ions were investigated. The size distribution of poly(ethylene glycol)-α-monomethyl-ω-5-[1,10]phenanthroline (mPEG_phen) was determined by electrospray ionization mass spectrometry (ESI-MS). Based on the measured ligand size distribution of mPEG_phen by ESI-MS, the 1:3 complex formation (Fe2+/mPEG_Phen) was computer-simulated as a pure random assembly process. The simulated distribution fits excellently to that of the complex Fe(mPEG_phen)32+ determined from the ESI-MS intensities. In addition, the collision-induced dissociation (CID) of the Fe(mPEG_phen)32+ complex was also studied by tandem mass spectrometry (ESI-MS/MS) and by computer simulation, as well. The ESI-MS/MS intensity distribution of the Fe(mPEG_phen)22+ formed from Fe(mPEG_phen)32+ by the loss of an mPEG_phen ligand under CID conditions fits quite well to the calculated one.

Graphical Abstract The complex formation of phenanthroline monofunctionalized poly(ethylene glycol) (mPEG_phen) with Fe(II)-ion and the collision induced dissociation of Fe(mPEG_phen)32+ were studied by electrospray mass spectrometry.Figure optionsDownload full-size imageDownload high-quality image (43 K)Download as PowerPoint slide