Figure 2.
Experimental IRMPD spectra (magenta trace) of (a) [Cu(bpy)2]2+ and (b) [Cu(bpy)2]+ generated using ETR and (c) [Cu(bpy)2]+ generated directly from ESI. The cyan traces represent spectra obtained with a Cu(I) salt (Cu-acetate) in the ESI solution, and the magenta traces are obtained with a Cu(II) salt (CuSO4). IRMPD spectra of [Cu(bpy)2]+ from all three sources appear to be identical (panels b and c). Both [Cu(bpy)2]2+ and [Cu(bpy)2]+ were irradiated with 4 macro pulses of the FEL to record their IRMPD spectra. Experimental spectra are overlaid with the theoretical linear IR spectra (black traces) for comparison. Their approximate IR mode descriptions are indicated. The horizontal dotted line indicates an apparent cutoff; bands with computed intensities below these levels are not observed in the experimental IRMPD spectrum, presumably due to the relatively high dissociation threshold of this complex. Such effects have been described in the literature.5,9,48,49