Infrared photodissociation spectroscopy of M(N2)n(+) (M = Y, La, Ce; n = 7-8) in the gas phase.

M(N2)n(+) (M = Y, La, Ce; n = 7-8) complexes have been studied by infrared photodissociation (IRPD) spectroscopy and density functional theory (DFT) calculations. The experimental results indicate that the N-N stretching vibrational frequencies are red-shifted from the gas-phase N2 value. The π back-donation is found to be a main contributor in these systems. IRPD spectra and DFT calculations reveal the coexistence of two isomers in the seven-coordinate M(N2)7(+) and eight-coordinate M(N2)8(+) complexes, respectively. The present studies on these metal-nitrogen complexes shed light on the interactions and coordinations toward N2 with transition and lanthanide metals.