Determination and gas‐phase stability evaluation of metal complexes by nanoelectrospray ionization and collision‐induced dissociation tandem mass spectrometry

Abstract

RationaleThe structures of metal complexes determine their stable functioning in product performance. Electrospray ionization mass spectrometry (ESI‐MS) is used in studying metal complexes despite exhibiting limitations in analyzing labile complexes. Therefore, identifying a method for detecting unstable complexes and evaluating their stabilities is necessary, providing a theoretical basis for material selection and performance evaluation.MethodsThe standard complexes Zn(BTZ)2, Fe(acac)3, and Sn(Oct)2 were analyzed using nanoESI quadrupole orbitrap MS (nanoESI‐MS) and compared with ESI‐MS for two temperature modes. The three complexes and alkylamine–Ag+ complexes were analyzed using nanoESI and collision‐induced dissociation MS/MS (CID‐MS/MS). Breakdown plots of the survival yield against collision energies expressed in terms of the center‐of‐mass were constructed according to the obtained product ion spectra. Quantum chemical calculations based on density functional theory were performed to calculate the binding energies between the alkylamines and Ag+.ResultsThe three standard complexes were detected in the native structures using nanoESI‐MS, confirming the advantage of nanoESI over ESI for detecting unstable complexes. The gas‐phase stabilities of the amine–Ag+ complexes, estimated using the breakdown plots constructed by plotting the data obtained via nanoESI and CID‐MS/MS, were consistent with the established theories, previous studies, and binding energies calculated using computational methods.ConclusionsNanoESI‐MS is suitable for detecting labile complexes and enables the structural analyses of unknown complex additives. A novel approach based on nanoESI and CID‐MS/MS was developed to determine the gas‐phase stabilities of complexes, enabling their quantification and comparison and providing a technical basis for product improvement, which is essential in developing industrial materials.