Tag: water oxidation

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)n clusters (bpy = 2,2′-bipyridine, tpy =2,2′:6′2″-terpyridine, n = 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.

DOI:  10.1021/acs.jpca.6b07668

Shuang Xu†, James E. T. Smith‡, and J. Mathias Weber‡

† JILA and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440, United States
‡ JILA and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0440, United States

Ligand Influence on the Electronic Spectra of Dicationic Ruthenium-Bipyridine-Terpyridine Complexes

We report electronic spectra of a series of ruthenium polypyridine complexes of the form [(trpy)(bipy)RuII–L]2+ (bipy = 2,2′-bipyridine and trpy = 2,2′:6′,2″-terpyridine), where L represents a small molecular ligand that occupies the last coordination site. Species with L = H2O, CO2, CH3CN, and N2 were investigated in vacuo using photodissociation spectroscopy. All species exhibit bright metal-to-ligand charger transfer (MLCT) bands in the visible and near UV, but with different spectral envelopes and peak energies, encoding the influence of the ligand L on the electronic structure of the complex. Several individual electronic bands can be resolved for L = H2O and CO2, while the spectra for L = N2 and CH3CN are more congested, even at low ion temperatures. The experimental results are discussed in the framework of time-dependent density functional theory.

DOI: 10.1021/acs.jpca.6b02926

Shuang Xu†, James E. T. Smith‡, and J. Mathias Weber‡

† JILA and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440, United States
‡ JILA and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0440, United States

Absorption Spectrum of a Ru(II)-Aquo Complex in Vacuo: Resolving Individual Charge-Transfer Transitions

Ruthenium(II) complexes are of great interest as homogeneous catalysts and as photosensitizers; however, their absorption spectra are typically very broad and offer only little insight into their electronic structure. We present the electronic spectrum of the aquo complex [(trpy)(bipy)RuII–OH2]2+ measured by photodissociation spectroscopy of mass-selected ions in vacuo (bipy = 2,2′-bipyridine and trpy = 2,2′:6′,2″-terpyridine). In the visible and near-UV, [(trpy)(bipy)RuII–OH2]2+ has several electronic bands that are not resolved in absorption spectra of this complex in solution but are partially resolved in vacuo. The experimental results are compared with results from time-dependent density functional theory calculations.
 
 
Shuang Xu†‡ and J. Mathias Weber*†§
† JILA, University of Colorado, 440 UCB, Boulder, Colorado 80309, United States
‡ Department of Physics, University of Colorado, Boulder, Colorado 80309, United States
§ Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States