Molecular complexes between F2 and OCS or CS2 and their role in photochemical matrix reactions

MELINA V. COZZARÍN; ROSANA M. ROMANO; HELGE WILLNER; CARLOS O. DELLA VÉDOVA

Córdoba

Workshop; Resmol, Reactividad y solvatación a nivel molecular; 2011

Molecular complexes between F2 and OCS or CS2 have been isolated in Ar matrices at low temperatures and characterized by FTIR spectroscopy, trough the codeposition of the monomers diluted in Ar. The experimental vibrational spectra were interpreted by comparison with the prediction of theoretical calculations. The SCO···F2 molecular complex was evidenced by an absorption at 2048 cm-1 in the FTIR spectrum, assigned to the carbonylic stretching mode of the OCS in the complex, shifted -2 cm-1 with respect to the same vibrational mode in the monomeric OCS. When F2 is codeposited with CS2, a feature at 1524 cm-1, -3 cm-1 shifted from the signal of free CS2, was assigned to the antisymmetric stretching of the CS2 of the CS2···F2 complex. In addition, an absorption centered at 867.7 cm-1 was attributed to the activation of the F-F stretching vibration in the complex (the activation of the n F-F was observed to occur at 851.7 cm-1 in the OCSe···F2 molecular complex isolated in solid Ar).[1] The structures of the complexes were optimized using the Gaussian 03 program system, and the IR spectra of the complexes and the monomers were simulated in order to compare them with the experimental findings. The binding energies of the molecular complexes were calculated using the correction proposed by Nagy et al.[2] The basis set superposition errors have been calculated by applying the counterpoise procedure developed by Boys and Bernardi.[3] The bonding properties of the complexes have been interpreted by a Natural Bond Orbital (NBO) analysis. The photochemically induced matrix reactions of F2 and OCS or CS2 lead to the formation of the hitherto unknowns FC(O)SF and FC(S)SF. The intermediacy of the van der Waals complexes seems to play an important role in the formation of the photoproducts.