14 research outputs found
Bright Luminescence in Three PhasesâA Combined Synthetic, Spectroscopic and Theoretical Approach
Combining phase-dependent photoluminescence (PL) measurements and quantum chemical calculations is a powerful approach to help understand the influence of the molecular surroundings on the PL properties. Herein, a phosphine functionalized amidinate was used to synthesize a recently presented bimetallic gold complex, featuring an unusual charge separation. The latter was subsequently used as metalloligand to yield heterotetrametallic complexes with an Au-M-M-Au âmolecular wireâ arrangement (M=Cu, Ag, Au) featuring metallophilic interactions. All compounds show bright phosphorescence in the solid state, also at ambient temperature. The effect of the molecular environment on the PL was studied in detail for these tetrametallic complexes by comparative measurements in solution, in the solid state and in the gas phase and contrasted to time-dependent density functional theory computations
Magnetic doping of the golden cage cluster \u3ci\u3eM\u3c/i\u3e@Au\u3csub\u3e16\u3c/sub\u3e\u3csup\u3eâ\u3c/sup\u3e (\u3ci\u3eM\u3c/i\u3e=Fe,Co,Ni)
Structural, electronic, and magnetic properties of the golden cage doped with a transition-metal atom, MAu16- (M =Fe,Co,Ni), are investigated using trapped ion electron diffraction, photoelectron spectroscopy, and density-functional theory. The best agreement to experiment is obtained for endohedral M@Au16- structures but with considerable distortions to the parent Au16- cage. Fe@Au16- and Co@Au16- are found to have similar structures with C2 symmetry while a C1 structure is obtained for Ni@Au16-. The 4s electrons are observed to transfer to the Au16 cage, whereas atomiclike magnetism due to the unpaired 3d electrons is retained for all the doped clusters
Structures of small bismuth cluster cations
The structures of bismuth cluster cations in the range between 4 and 14 atoms have been assigned by a combination of gas phase ion mobility and trapped ion electron diffraction measurements together with density functional theory calculations. We find that above 8 atoms the clusters adopt prolate structures with coordination numbers between 3 and 4 and highly directional bonds. These open structures are more like those seen for clusters of semiconducting-in-bulk elements (such as silicon) rather than resembling the compact structures typical for clusters of metallic-in-bulk elements. An accurate description of bismuth clusters at the level of density functional theory, in particular of fragmentation pathways and dissociation energetics, requires taking spin-orbit coupling into account. For n = 11 we infer that low energy isomers can have fragmentation thresholds comparable to their structural interconversion barriers. This gives rise to experimental isomer distributions which are dependent on formation and annealing histories
Effect of Proton Substitution by Alkali Ions on the Fluorescence Emission of Rhodamine B Cations in the Gas Phase
The
photophysics of chromophores is strongly influenced by their
environment. Solvation, charge state, and adduct formation significantly
affect ground and excited state energetics and dynamics. The present
study reports on fluorescence emission of rhodamine B cations (RhBH<sup>+</sup>) and derivatives in the gas phase. Substitution of the acidic
proton of RhBH<sup>+</sup> by alkali metal cations, M<sup>+</sup>,
ranging from lithium to cesium leads to significant and systematic
blue shifts of the emission. The gas-phase structures and singlet
transition energies of RhBH<sup>+</sup> and RhBM<sup>+</sup>, M =
Li, Na, K, Rb, and Cs, were investigated using HartreeâFock
theory, density functional methods, second-order MøllerâPlesset
perturbation theory, and the second-order approximate coupled-cluster
model CC2. Comparison of experimental and theoretical results highlights
the need for improved quantum chemical methods, while the hypsochromic
shift observed upon substitution appears best explained by the Stark
effect due to the inhomogeneous electric field generated by the alkali
ions
Gas-Phase Photoluminescence Characterization of Stoichiometrically Pure Nonanuclear Lanthanoid Hydroxo Complexes Comprising Europium or Gadolinium
Gas-phase
photoluminescence measurements involving mass-spectrometric techniques
enable determination of the properties of selected molecular systems
with knowledge of their exact composition and unaffected by matrix
effects such as solvent interactions or crystal packing. The resulting
reduced complexity facilitates a comparison with theory. Herein, we
provide a detailed report of the intrinsic luminescence properties
of nonanuclear europiumÂ(III) and gadoliniumÂ(III) 9-hydroxyÂphenalen-1-one
(HPLN) hydroxo complexes. Luminescence spectra of [Eu<sub>9</sub>(PLN)<sub>16</sub>(OH)<sub>10</sub>]<sup>+</sup> ions reveal an europium-centered
emission dominated by a 4-fold split Eu<sup>III</sup> hypersensitive
transition, while photoluminescence lifetime measurements for both
complexes support an efficient europium sensitization via a PLN-centered
triplet-state manifold. The combination of gas-phase measurements
with density functional theory computations and ligand-field theory
is used to discuss the antiprismatic core structure of the complexes
and to shed light on the energy-transfer mechanism. This methodology
is also employed to fit a new set of parameters, which improves the
accuracy of ligand-field computations of Eu<sup>III</sup> electronic
transitions for gas-phase species
Vibronic Coupling Analysis of the Ligand-Centered Phosphorescence of Gas-Phase Gd(III) and Lu(III) 9âOxophenalen-1-one Complexes
The gas-phase laser-induced
photoluminescence of cationic mononuclear
gadolinium and lutetium complexes involving two 9-oxophenalen-1-one
ligands is reported. Performing measurements at a temperature of 83
K enables us to resolve vibronic transitions. Via comparison to FranckâCondon
computations, the main vibrational contributions to the ligand-centered
phosphorescence are determined to involve rocking, wagging, and stretching
of the 9-oxophenalen-1-oneâlanthanoid coordination in the low-energy
range, intraligand bending, and stretching in the medium- to high-energy
range, rocking of the carbonyl and methine groups, and CâH
stretching beyond. Whereas FranckâCondon calculations based
on density-functional harmonic frequency computations reproduce the
main features of the vibrationally resolved emission spectra, the
absolute transition energies as determined by density functional theory
are off by several thousand wavenumbers. This discrepancy is found
to remain at higher computational levels. The relative energy of the
GdÂ(III) and LuÂ(III) emission bands is only reproduced at the coupled-cluster
singles and doubles level and beyond
Characterization of Nonanuclear Europium and Gadolinium Complexes by Gas-Phase Luminescence Spectroscopy
Gas-phase measurements
using mass-spectrometric techniques allow
determination of the luminescence properties of selected molecular
systems with knowledge of their exact composition. Furthermore, isolated
luminophores are unaffected by matrix effects like solvent interactions
or crystal packing. As a result, the system complexity is reduced
relative to the condensed phase and a direct comparison with theory
is facilitated. Herein, we report the intrinsic luminescence properties
of nonanuclear europiumÂ(III) and gadoliniumÂ(III) 9-hydroxyphenalen-1-one
(HPLN)âhydroxo complexes. Luminescence spectra of [Eu<sub>9</sub>(PLN)<sub>16</sub>(OH)<sub>10</sub>]<sup>+</sup> ions reveal an europium-centered
emission dominated by a 4-fold split EuÂ(III) hypersensitive transition.
The corresponding GdÂ(III) complex, [Gd<sub>9</sub>(PLN)<sub>16</sub>(OH)<sub>10</sub>]<sup>+</sup>, shows a broad emission from a ligand
based triplet state with an onset of about 1000 wavenumbers in excess
of the europium emission. As supported by photoluminescence lifetime
measurements for both complexes, we deduce an efficient europium sensitization
via PLN-based triplet states. The luminescence spectra of the complexes
are discussed in terms of a square antiprismatic europium/gadolinium
core structure as suggested by density functional computations
Substitutional Photoluminescence Modulation in Adducts of a Europium Chelate with a Range of Alkali Metal Cations: A Gas-Phase Study
We present gas-phase dispersed photoluminescence
spectra of europiumÂ(III) 9-hydroxyphenalen-1-one (HPLN) complexes
forming adducts with alkali metal ions ([EuÂ(PLN)<sub>3</sub>M]<sup>+</sup> with M = Li, Na, K, Rb, and Cs) confined in a quadrupole
ion trap for study. The mass selected alkali metal cation adducts
display a split hypersensitive <sup>5</sup>D<sub>0</sub> â <sup>7</sup>F<sub>2</sub> Eu<sup>3+</sup> emission band. One of the two
emission components shows a linear dependence on the radius of the
alkali metal cation whereas the other component displays a quadratic
dependence thereon. In addition, the relative intensities of both
components invert in the same order. The experimental results are
interpreted with the support of density functional calculations and
JuddâOfelt theory, yielding also structural information on
the isolated [EuÂ(PLN)<sub>3</sub>M]<sup>+</sup> chromophores