Kathryn A. Antle

Matrix isolation infrared spectroscopy has been combined with MP2/aug‘-cc-pVDZ calculations to characterize the 1:1 hydrogen-bonded complexes between H2O2 and the hydrogen halides HF, HCl, and HBr. The infrared spectra of the these complexes are characterized by an intense, red-shifted H−X stretching band, as well as slight perturbations to several of the HOOH vibrational bands. For the HF complex, the intermolecular librational modes were also observed. The ab initio calculations identified two equilibrium structures on each surface, one an open structure, and the other cyclic. These two structures have similar binding energies. However, only the open structure appears to be present in argon and nitrogen matrices. This open structure is preferentially stabilized by interaction of its larger dipole moment with the matrix medium.

The matrix-isolation technique has been combined with infrared spectroscopy to identify and characterize the products formed by irradiation of cage-paired CrCl(2)O(2) and a series of chloroethenes, C(2)H(x)()Cl(y)() (x + y = 4). For each system, oxygen-atom transfer occurred upon irradiation, yielding the corresponding acetyl chloride derivative and the Cl(2)CrO species. The products were formed in the same matrix cage and strongly interacted to form a distinct molecular complex after formation. Three different modes of interaction were explored computationally: eta(1) to the oxygen atom, eta(2) to the C=O bond, and eta(1) to the chlorine atom. In addition, a five-membered metallocycle and the chloroepoxide species were considered. No evidence was obtained for the chloroacetaldehyde derivative, indicating the occurrence of oxygen-atom attack at the more substituted carbon of the chloroethene. Evidence tentatively supporting the formation of the metallocycle was obtained as well. Theoretical calculations indicated that the acetyl chloride derivative was approximately 10 kcal/mol more stable than the corresponding chloroacetaldehyde species for each system at the B3LYP/6-311++g(d,2p) level of theory. The binding energy of each of the complexes was also found to be near 10 kcal/mol at this level of theory.