High Kinetic Stability of HXeBr upon Interaction with Carbon Dioxide: HXeBr•••CO2 Complex in a Xenon Matrix and HXeBr in a Carbon Dioxide Matrix

We investigate the conditions when noble-gas hydrides can be found in real environments and report on the preparation and identification of the HXeBr center dot center dot center dot CO2 complex in a xenon matrix and HXeBr in a carbon dioxide matrix. The H-Xe stretching mode of the HXeBr center dot center dot center dot CO2 complex in a xenon matrix is observed at 1557 cm(-1), showing a spectral shift of +53 cm(-1) from the HXeBr monomer. The calculations at the CCSD(T)/aug-cc-pVTZ-PP(Xe,Br) level of theory give two stable structures for the HXeBr center dot center dot center dot CO2 complex with frequency shifts of +55 and +103 cm(-1), respectively. On the basis of the calculations, the experimentally observed band is assigned to the more stable structure with a "parallel" geometry. The HXeBr molecule was prepared in a carbon dioxide matrix and has the H-Xe stretching frequency of 1646 cm(-1), meaning a strong matrix shift and stabilization of the H-Xe bond. The deuterated species DXeBr in a carbon dioxide matrix absorbs at 1200 cm(-1). This is the first case where a noble-gas hydride is prepared in a molecular solid. The thermal stabilities of HXeBr and HXeBr center dot center dot center dot CO2 complex in a xenon matrix and HXeBr in a carbon dioxide matrix were examined. We have found a high thermal stability of HXeBr in carbon dioxide ice (at least up to 100 K), i.e., under conditions that may occur in nature.