Structures of methanol molecules chemisorbed on cobalt cluster ions, Co(n)(+) (n=2-6), were investigated by infrared photodissociation (IR-PD) spectroscopy in the wavenumber range of 3400-4000 cm(-1). All the IR-PD spectra measured exhibit an intense peak in the region of the OH stretching vibration. In the IR-PD spectra of Co(2)(+) (CH(3)OH)(2,3) and Co(3)(+) (CH(3)OH)(3), weak peaks were observed additionally in the vicinity of 3000 cm(-1), being assignable to the CH stretching vibration. The comparison of the experimental results with the calculated ones leads us to conclude that (1) molecularly chemisorbed species, Co(n)(+)(CH(3)OH)(m) (m=1-3), and dissociatively chemisorbed species, Co(n)(+) (CH(3)OH)(m-1) (CH(3))(OH), are dominant and (2) the methanol dehydrogenation proceeds via an intermediate, Co(n)(+) (CH(3)) (OH). (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3121503]