Knowledge Bank

The heteronuclear diatomic metal ions CrV$\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ and MoV$\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ were investigated using negative ion photoelectron spectroscopy. These bare, heteronuclear group 5 and 6 transition metal dimers allow the study of multiple metal-metal bonding free of ligand effects. The photoelectron spectra, obtained at 488 nm with an instrumental resolution of about 5 meV (40 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$), provide measurements of the electron affinities, vibrational frequencies for both the anion and neutral states, bond length changes upon electron detachment, excited electronic state energies and spin-orbit splittings. The CrV$\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ and MoV$\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ spectra display transitions to the multiply-bonded $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta$ $(d\pi )4(d\delta )3(d\sigma )2(s\sigma )2$ ground states of the neutral molecules and to several excited states. Addition of an electron to the vacant $\sigma \ast$ orbital gives the $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta$ anion, which is found to be the ground state of CrV$\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ but a low lying excited state of MoV$\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$. Addition of a d$\delta$ electron yields the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma +$ MoV$\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ ground state. Density functional theory calculations of the anions and neutrals were performed to help elucidate the spectroscopic assignments and observed periodic trends.