The infrared spectroscopy of gaseous ions Fe(CH3OCH3)(+) and Fe(CH3OCH2CH2OCH3)(+) (n = 1-2) has been studied in the 800-2000 cm(-1) energy range using the coupling of the free electron laser CLIO and an FTICR mass spectrometer, and compared to spectra calculated by ab initio quantum chemistry. The match between experimental and theoretical infrared spectra appears to be very good, the experimental spectra corresponding to the most stable structure predicted by the calculations. Characteristic absorption bands of functional groups have been evidenced, allowing this coupling to be a very powerful tool for structure elucidation in the gas phase. (C) 2003 Elsevier B.V. All rights reserved.