Infrared Photodissociation of Hydrogen-Bonded Complexes Trapped in Inert Matrices. The Ethylene Oxide-Hydrogen Iodide System

Article abstract of DOI:10.1021/j100337a010

Matix isolation infrared spectroscopy applied to the ethylene oxide/H(D)I system trapped in solid Ar and N2 allows identification of several kinds of hydrogen-bonded complexes: a 1:1 species which exists under different structures and larger aggregates giving rise to proton transfer with formation of ionic species of the type <(EO)2H>⁺ or (IHI)^- characterized by quasi-symmetrical single-minimum potential functions for the proton (proton sharing).The interconversion between the hydrogen-bonded (C) and the non-hydrogen-bonded (U) form of the 1:1 complex is seen to depend on two parameters: temperature and infrared irradiation.Kinetic measurements of the disappearance (or appearance) of C have shown that the C->U conversion is mainly induced by IR radiations in the range 1500-2300 cm^-1, corresponding to the excitation of ν_s (HI stretching mode), while the C<-U transformation is thermally induced above 17 K.From the temperature dependence of the kinetic rate constant an activation energy for C<-U conversion has been obtained.The effect of HI/DI isotopic substitution is also discussed.The very slow C->U conversion rate with DI suggests a barrier greater than 1500 cm^1- for this photoprocess.