Energetics of the ligated vanadium dications VO2+, VOH2+, and [V,O,H2]2+

Charge-stripping mass spectrometry and electronic structure calculations are combined to examine the energetics of the vanadium-containing dications VO2+, VOH2+, [HVOH]2+, and [V(OH2)]2+. Energy-resolved measurements, in conjunction with quantum-mechanical calculations, led to ionization energies (IE) of (VO+) = 16.6 +/- 0.3 eV and IE(VOH+) = 16.0 +/- 0.4 eV. Born-Haber cycles reveal that VO2+ and VOH2+ are both thermochemically stable dications with respect to their charge-separation asymptotes. Depending on the mode of ion generation, the [V,O,H2]+ monocations are formed as variable mixtures of the structural isomers [HVOH]+ and [V(OH2)]+. The measured IE([V,O,H2]+) = 13.7 +/- 0.3 eV is between the theoretical predictions for these isomers, indicating that mixtures of both isomers are sampled in the experiments. According to the theoretical results, [V(OH2)]2+ is also a thermochemically stable dication, whereas [HVOH]2+ is suggested to be metastable.