An infrared multiple photon dissociation (IRMPD) vibrational spectrum of the gas-phase copper(II) L-histidine complex has been obtained.  Two species, CuHis1 and CuHis2, are very close in Gibbs free energy, and both have computed vibrational spectra in good agreement with the experimentally observed IRMPD spectrum. 
IRMPD
This spectrum was compared to lowest-energy computational spectra obtained at the B3LYP/6-311+G** level of theory. 
B3LYP/6-311+G**