A Water-Soluble Xe@cryptophane-111 Complex Exhibits Very High Thermodynamic Stability and a Peculiar ~(129)Xe NMR Chemical Shift

摘要

The known xenon-binding (±)-cryptophane-111 (1) has been functionalized with six [(η~5-C_5Me_5)Ru~(II)]~+ ([Cp*Ru]~+) moieties to give, in 89% yield, the first water-soluble cryptophane-111 derivative, namely [(Cp*Ru)_61]Cl_6 ([2] Cl_6). [2]Cl_6 exhibits a very high affinity for xenon in water, with a binding constant of 2.9(2) × 104 M~(-1) as measured by hyperpolarized ~(129)Xe NMR spectros-copy. The ~(129)Xe NMR chemical shift of the aqueous Xe@[2]~(6+) species (308 ppm) resonates over 275 ppm downfield of the parent Xe@1 species in (CDC-2)_2and greatly broadens the practical~( 129)Xe NMR chemical shift range made available by xenon-binding molecular hosts. Single crystal structures of [2][CF_3SO_3]_6·xsolvent and 0.75H_2O@1 ·2CHCl_3 reveal the ability of the cryptophane-111 core to adapt its conformation to guests.