(CD3CN)2H+ adducts in anhydrous H3PW12O40: a FTIR study

Abstract

The interaction of CD₃CN with dehydrated H₃PW₁₂O₄₀ in solid form has been studied by IR spectroscopy, and results are compared with those obtained for other CD₃CN/acidic or CD₃CN/superacidic solid systems (like zeolites in the acidic form and the perfluorosulfonic membrane H-NAFION). The formation of CD₃CN···H⁺···NCCD₃ adducts is demonstrated. These species are characterised by a characteristic band at 2330 cm⁻¹ and by a very broad absorption below 2000 cm⁻¹. On the basis of theoretical DFT ab initio calculations and by comparison with experimental results obtained on the analogous H₅O₂⁺ adducts, the above bands are assigned respectively to the ν(CN) and to the ν(N···H⁺···N) modes of the protonated (CD₃CN)₂H⁺ dimers.