Gold(II) complexes are rare and their application for catalysis of chemical transformations is unexplored. The reason is their easy oxidation or reduction to the more stable gold(III) or gold(I) complexes, respectively. We explored the thermodynamics of the formation of the [(L)Au II X] + complexes (L = ligand, X = halogen) from their gold(III) precursors and investigated the stability and the spectral properties in the IR and VIS range of the formed gold(II) complexes in the gas phase. The results show that the best ancillary ligands L for stabilizing gaseous [(L)Au II X] + complexes are bidentate and tridentate ligands with nitrogen donor atoms. The electronic structure and spectral properties of the investigated gold(II) complexes were correlated with the quantum chemical calculations. The results show that the molecular and electronic structure of the gold(II) complexes as well as their spectroscopic properties are very similar to the analogous stable copper(II) complexes.

The structural elucidation of metabolite molecules is important in many branches of the life sciences. However, the isomeric and isobaric complexity of metabolites makes their identification extremely challenging, and analytical standards are often required to confirm the presence of a particular compound in a sample. We present here an approach to overcome these challenges using high-resolution ion mobility spectrometry in combination with cryogenic vibrational spectroscopy for the rapid separation and identification of metabolite isomers and isobars. Ion mobility can separate isomeric metabolites in tens of milliseconds, and cryogenic IR spectroscopy provides highly structured IR fingerprints for unambiguous molecular identification. Moreover, our approach allows one to identify metabolite isomers automatically by comparing their IR fingerprints with those previously recorded in a database, obviating the need for a recurrent introduction of analytical standards. We demonstrate the principle of this approach by constructing a database composed of IR fingerprints of eight isomeric/isobaric metabolites and use it for the identification of these isomers present in mixtures. Moreover, we show how our fast IR fingerprinting technology allows to probe the IR fingerprints of molecules within just a few seconds as they elute from an LC column. This approach has the potential to greatly improve metabolomics workflows in terms of accuracy, speed, and cost.

Gold(II) complexes are rare and their application for catalysis of chemical transformations is unexplored. The reason is their easy oxidation or reduction to the more stable gold(III) or gold(I) complexes, respectively. We explored the thermodynamics of the formation of the [(L)AuIIX]+ complexes (L = ligand, X = halogen) from their gold(III) precursors and investigated the stability and the spectral properties in the IR and VIS range of the formed gold(II) complexes in the gas phase. The results show that the best ancillary ligands L for stabilizing gaseous [(L)AuIIX]+ complexes are bidentate and tridentate ligands with nitrogen donor atoms. The electronic structure and spectral properties of the investigated gold(II) complexes were correlated with the quantum chemical calculations. The results show that the molecular and electronic structure of the gold(II) complexes as well as their spectroscopic properties are very similar to the analogous stable copper(II) complexes.