Tag: gas phase

Intrinsic photophysics of nitrophenolate ions studied by cryogenic ion spectroscopy

The intrinsic photophysics of nitrophenolate isomers (meta, para, and ortho) was studied at low temperature using photodissociation mass spectrometry in a cryogenic ion trap instrument. Each isomer has distinct photophysics that affects the excited state lifetimes, as observed experimentally in their spectroscopic linewidths. Visible-light-induced excitation of m-nitrophenolate gives rise to well-resolved vibronic features in the spectrum of the S1 state. The para and ortho isomers have broad spectra – even at cryogenic temperatures – due to their shorter excited state lifetimes and spectral congestion. We present computational evidence for mixing of the first and second excited states of o-nitrophenolate, leading to significant additional broadening in the experimental spectrum.

DOI: 10.1039/C8CP06078A

Leah G. Dodson,a  Wyatt Zagorec-Marks,b  Shuang Xu,c  James E. T. Smithb  and  J. Mathias Weberb  

aJILA and NIST, University of Colorado, 0440 UCB, Boulder, USA
bJILA and Department of Chemistry, University of Colorado, 0440 UCB, Boulder, USA
cJILA and Department of Physics, University of Colorado, 0440 UCB, Boulder, USA

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.

DOI: 10.1021/acs.inorgchem.7b00620

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

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 [MII(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.

DOI: 10.1021/acs.inorgchem.6b02054

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

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

The electronic spectrum of cryogenic ruthenium-tris-bipyridine dications in vacuo

We report the electronic spectrum of the prototypical ruthenium coordination complex Ru(bpy) 2+ (bpy = 2, 2′-bipyridine) by messenger tagging with N in a cryogenic ion trap and photodissociation spectroscopy of mass selected Ru(bpy) 2+ ⋅ N ions. We observe individual electronic bands and groups of bands with unprecedented detail, particularly in the usually unresolved metal-to-ligand charge transfer region of thespectrum. By comparing our experimental results with time-dependent density functional theory, both with and without spin-orbit interaction [Heully , J. Chem. Phys. , 184308 (2009)], we are able to assign the spectrum of the isolated ion.

DOI:  10.1063/1.4955262

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