Relationship between proton affinities and structures of proton-bound dimers

This work presents a structural approach for determination of proton affinities of molecules. In proton-bound dimer [X…H…M]⁺, M and X compete with each other to capture the proton. The correlation between proton affinities of a series of molecules, M, and X…H bond length was studied while X was a common molecule in the all proton-bound dimers. Linear relationships were observed between proton affinities of a series of alcohols, ethers, aldehydes, ketones and amines and X…H bond length, where H₂O and HF were used as X. The method was employed for the measurement of proton affinities of (HF)_1-10 clusters using NH₃ and H₂O as common molecules, [NH₃…H…(HF)_n]⁺ and [H₂O…H…(HF)_n]⁺. A linear correlation was observed for the PAs of (HF)_n clusters versus N…H bond length.