Unsaturated cryptophanes: Toward dual PHIP/hyperpolarised xenon sensors

Cryptophanes, cage‐molecules constituted of aromatic bowls, are now well recognised as powerful xenon hosts in 129Xe NMR‐based biosensing. In the quest of a dual probe that can be addressed only by NMR, we have studied three cryptophanes bearing a tether with an unsaturated bond. The idea behind this is to build probes that can be detected both via hyperpolarised 129Xe NMR and para‐hydrogen induced polarisation 1H NMR. Only two of the three cryptophanes experience a sufficiently fast hydrogenation enabling the para‐hydrogen induced polarisation effect. Although the in–out xenon exchange properties are maintained after hydrogenation, the chemical shift of xenon encaged in these two cryptophanes is not strikingly modified, which impedes safe discrimination of the native and hydrogenated states via 129Xe NMR. However, a thorough examination of the hyperpolarised 1H spectra reveals some interesting features for the catalytic process and gives us clues for the design of doubly smart 1H/129Xe NMR‐based biosensors. The concept of dual NMR sensors based on simultaneous detection of hyperpolarised 129Xe and para‐hydrogen induced polarisation is investigated by means of three probes, constituted of an aromatic cage‐molecule reversibly hosting xenon and bearing a tether with an unsaturated bond. These molecules give clues on the catalytic process and for the design of smart 1H/129Xe NMR‐based (bio)sensors.