Probing the self assembly, reactivity and structure of supramolecular architectures using high resolution mass spectrometry

Electrospray (ESI-MS) and cryospray mass spectrometry (CSI-MS) techniques were developed to analyse and investigate the self-assembly, reactivity and structure of supramolecular architectures. Using ESI-MS, the complexation reactions of the ligand cis,trans-1,3,5-tris(pyridine-2-carboxaldimino)cyclohexane (ttop) with divalent first row transition metal salts to form complexes with nuclearities 1,2 and 4 were followed. In-situ mass spectrometry was also utilised to show the stepwise formation of the ligand-metal complexes. Mass spectrometry has been used to identify the reactive species in the catalytic oxidation of conventionally hard to activate C-H and C=C moieties. The identity of the reactive species under catalytic conditions has been postulated as Fe(V)=O but direct observation of this species has not been possible before. Using cryospray mass spectrometry, the Fe(V)=O reactive intermediate within the synthetic [FeV(O)(OH)(PyMe2tacn)]+ (PyMe2tacn = 1-(2’-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane) complex at -40 ºC and its reaction with an olefin was observed. Oxygen atom transfer from H2O2 / H2O was followed through Fe(V)=O to the products with isotopic labelling, and the reactivity was probed as a function of temperature. Mass spectrometry has been used as both a qualitative and quantitative tool to deduce the stoichiometry of an anion receptor and the corresponding anion. Job plots of mass spectrometry data have been compared to the conventional 1H NMR job plot data to give corresponding results therefore providing evidence of the use of mass spectrometry as a quantitative and qualitative analytical tool. Mass spectrometry has been used to follow the formation of heterometallic complexes and provide evidence of their building block in solution. The formation of the complexes has been followed using time-resolved mass spectrometry experiments and the building blocks analysed