Photodissociation and theoretical studies of the Au+–(C5H5N) complex

Abstract

Laser vaporization combined with a supersonic molecular beam was employed to generate and study the Au(C₅H₅N)⁺ complex for the first time. On the basis of the ionization energies (IE) between gold and pyridine, the Au(C₅H₅N)⁺ species is viewed as being a Au⁺–C₅H₅N species. Photodissociative charge transfer was observed with exclusive C₅H₅N⁺ (pyridine) formation. The photofragmentation spectrum of Au⁺–(C₅H₅N) was scanned by monitoring the pyridine fragments. A structureless continuum spectrum was observed and the onset of C₅H₅N⁺ appearance indicates the upper limit on the Au⁺–C₅H₅N bond strength to be 59.6 kcal mol⁻¹. Ab initio calculations at the MP2 level were employed to optimize the geometries of the gold complexes and binding energies were obtained using CCSD(T) single point calculations. Besides from the C_2v structure observed in Cu⁺ and Ag⁺ complexes, the theoretical results yielded a second isomer with C₁ symmetry which is 24 kcal mol⁻¹ less stable in energy than the C_2v isomer.