Investigation of competing interactions in alkali metal ion–acetone–water clusters

Competitive interactions were investigated in M+(Acetone)n(H2O)m cluster ions for M = Na and K. Different [n, m] combinations were characterized by infrared predissociation spectroscopy. When n + m = 4 for Na+, shifts in the water O–H stretch modes demonstrate that the acetone weakens the ion–water interaction but does not alter the solvent configuration around the ion. For K+ at this size, the acetone weakens the ion–water interaction to the extent that hydrogen bonds are formed. When n + m = 5 for both ions, O–H frequency shifts indicate that hydrogen bonds in the immediate ionic environment are weakened by the presence of acetone.