Experimental and theoretical studies on the complexes of [Pb(m)-pyridyl]- (m = 1-4).

The pyridyl-lead complexes Pb(m)-C5H4N (m = 1-4), which are produced from the reactions between lead clusters formed by laser ablation and the pyridine molecules seeded in argon carrier gas, are studied by photoelectron (PE) spectra and density functional theory. The adiabatic electron affinity (EA) of Pb(m)C5H4N is obtained from PE spectra at photon energies of 308 and 193 nm. Theoretical calculation is carried out to elucidate their structures and bonding modes. A variety of geometries for the isomers are optimized to search for the lowest-energy geometry. By comparing the theoretical results, including the EA and simulated density of state spectra, with the experimental determination, the lowest-energy structures for each species are obtained. The following analysis of the molecular orbital composition provides the evidence that the pyridyl binds on lead clusters through the Pb-C sigma bond. Moreover, there is an apparent spin-state transition from triplet state toward singlet state for the ground-state structure of Pb(m)C5H4N with an increase of lead cluster.