Month: November 2015

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
 

Ligand influence on the electronic spectra of monocationic copper–bipyridine complexes

We present photodissociation spectroscopy and computational analysis of three monocationic Cu–bipyridine complexes with one additional ligand of different interaction strength (N2, H2O and Cl) in the visible and UV. All three complexes show similar ππ* bands with origins slightly above 4 eV and vibrational band contours that are due to bipyridine ring deformation modes. Experiments at low temperature show that excited-state lifetime is the limiting factor for the width of the vibrational features. In the case of Cl as a ligand, there is a lower lying bright ligand-to-ligand charge-transfer state around 2.75 eV. The assignment of the transitions was made based on equation-of-motion coupled-cluster calculations. While the nature of the ligand does not significantly change the position of the bright ππ* state, it drastically changes the excited-state dynamics.
 

DOI: 10.1039/C5CP05063D

Shuang Xu,a   Samer Gozem,b   Anna I. Krylov,b  Casey R. Christopherc and   J. Mathias Weber*c
 aJILA and Department of Physics, University of Colorado, Boulder, USA
bDepartment of Chemistry, University of Southern California, Los Angeles, USA
cJILA and Department of Chemistry and Biochemistry, University of Colorado, Boulder, USA
* weberjm@jila.colorado.edu