UV Spectra of Tris(2,2′-bipyridine)–M(II) Complex Ions in Vacuo (M = Mn, Fe, Co, Ni, Cu, Zn)

We present electronic spectra in the π–π* region of a series of tris­(bpy)–M­(II) complex ions (bpy = 2,2′-bipyridine; M = Mn, Fe, Co, Ni, Cu, Zn) in vacuo for the first time. By applying photodissociation spectroscopy to cryogenically cooled and mass selected [M^II(bpy)₃]²⁺ ions, we obtain the intrinsic spectra of these ions at low temperature without perturbation by solvent interaction or crystal lattice shifts. This allows spectroscopic analysis of these complex ions in greater detail than possible in the condensed phase. We interpret our experimental data by comparison with time-dependent density functional theory

Hydration of a Binding Site with Restricted Solvent Access: Solvatochromic Shift of the Electronic Spectrum of a Ruthenium Polypyridine Complex, One Molecule at a Time

We report the electronic spectra of mass selected [(bpy)­(tpy)­Ru–OH₂]²⁺·(H₂O)<i>_n</i> clusters (bpy = 2,2′-bipyridine, tpy =2,2′:6′2″-terpyridine, <i>n</i> = 0–4) in the spectral region of their metal-to-ligand charge transfer bands. The spectra of the mono- and dihydrate clusters exhibit partially resolved individual electronic transitions. The water network forming at the aqua ligand leads to a rapid solvatochromic shift of the peak of the band envelope: addition of only four solvent water molecules can recover 78% of the solvatochromic shift in bulk solution. The sequential shift of the band shows a clear change in behavior with the closing of the first hydration shell. We compare our experimental data to density function theory (DFT) calculations for the ground and excited states

Electronic Spectra of Tris(2,2′-bipyridine)-M(II) Complex Ions in Vacuo (M = Fe and Os)

We measured the electronic spectra of mass-selected [M­(bpy)₃]²⁺ (M = Fe and Os, bpy = 2,2′-bipyridine) ions in vacuo by photodissociation spectroscopy of their N₂ adducts, [M­(bpy)₃]²⁺·N₂. Extensive band systems in the visible (predominantly charge transfer) and near-ultraviolet (ππ*) spectral regions are reported. The [M­(bpy)₃]²⁺·N₂ target ions were prepared by condensing N₂ onto electrosprayed ions in a cryogenic ion trap at ca. 25 K and then mass-selected by time-of-flight mass spectrometry. The electronic photodissociation spectra of the cold, gas-phase ions closely reflect their intrinsic properties, i.e., without perturbation by solvent effects. The spectra are interpreted using time-dependent density functional theory calculations both with and without accounting for relativistic effects