The preservation of sarin and O,O’-diisopropyl fluorophosphate inside coordination cage hosts

The host-guest chemistry of O,O-diisopropyl fluorophosphate (DFP), a phosphonofluoridate G-series chemical warfare agent simulant, in the presence of a number of octanuclear cubic coordination cages was investigated. The aim was to demonstrate cage-catalysed hydrolysis of DFP at near neutral pH, however, two octanuclear coordination cages, HPEG (containing water solubilising PEG groups) and HW (containing water solubilising hydroxymethyl groups), were actually found to increase the lifetime of DFP in aqueous buffer solution (pH 8.7). Crystallographic analysis of DFP with a structurally related cage revealed that DFP binds to windows in the cage surface, not the internal cavity, with the phosphorus-fluorine bond directed into the cavity rather than towards the external environment, with the cage/DFP association protecting DFP from hydrolysis. Initial studies with the chemical warfare agent (CWA) sarin (GB) with HPEG cage in a buffered solution also drastically reduced the rate of hydrolysis. The ability of these cages to inhibit the hydrolysis of these P-F bond containing organophosphorus guests, by encapsulation, may have applications in forensic sample preservation and analysis.