Linear hydrogen-bonded complexes of carbon dioxide with the rare-gas compounds HArF and HKrF were found to be stable at the MP2/6-311++G(2d,2p) level of theory. The (FArHOCO)-O-... and (FKrHOCO)-O-... complexes have zero-point energy corrected binding energies of 13 and 8 kJ mol(-1), respectively. Large blue shifts of the Rg-H harmonic stretching frequency and red shifts of the F-Rg stretch were obtained for both complexes. The electron density rearrangement on complexation was also examined. A perturbation theory model of frequency shifts was found to be in good agreement with the ab initio results. (c) 2005 Elsevier B.V. All rights reserved.