Inelastic neutron scattering of model compounds for surface formates Potassium formate, copper formate and formic acid

Abstract

As a prelude to the study of surface formate species with inelastic neutron scattering (INS) we have used INS to obtain the vibrational spectra of the model compounds potassium formate (KHCOO), anhydrous copper formate [Cu(HCOO) ₂ ], hydrated copper formate [Cu(HCOO) ₂ ·4H ₂ O] and formic acid. These data are compared to IR and Raman spectra. In INS we observe vibrational modes for both potassium and copper formate not previously reported in IR and Raman studies, including a librational mode of copper formate at ca. 600 cm ^-1 . The relative intensities of the formate bands are very different from those observed in IR and Raman spectra and vary considerably between the three compounds studied. The two most intense formate fundamental vibrations in the INS spectrum are the C–H out-of-plane bend and the C–H in-plane bend, both of which have low intensity in IR and Raman spectra. In the INS spectrum the relative intensities of these modes vary considerably between the compounds studied indicating a structural dependency of the INS intensities.