On the Hydrogen Oxalate Binding Motifs onto Dinuclear Cu and Ag Metal Phosphine Complexes

We report the binding geometries of the isomers that are formed when the hydrogen oxalate ((CO$_{2}$)$_{2}$H=HO$_{x}$) anion attaches to dinuclear coinage metal phosphine complexes of the form [M$_{1}$M$_{2}$dcpm$_{2}$(HOx)]$^{+}$ with M=Cu, Ag and dcpm=bis(dicyclohexylphosphino)methane, abbreviated [MM]$^{+}$. These structures are established by comparison of isomer-selective experimental vibrational band patterns displayed by the cryogenically cooled and N$_{2}$-tagged cations with DFT calculations of the predicted spectra for various local minima. Two isomeric classes are identified that feature either attachment of the carboxylate oxygen atoms to the two metal centers (end-on docking) or attachment of oxygen atoms on different carbon atoms asymmetrically to the metal ions (side-on docking). Within each class, there are additional isomeric variations according to the orientation of the OH group. This behavior indicates that HOx undergoes strong and directional coordination to [CuCu]$^{+}$ but adopts a more flexible coordination to [AgAg]$^{+}$. Infrared spectra of the bare ions, fragmentation thresholds and ion mobility measurements are reported to explore the behaviors of the complexes at ambient temperature

Cryo Kinetics of N2N_2 Adsorption to Isolated Cationic Iron Clusters and Cryo IR Spectroscopy of the N2N_2 Adsorbates

This thesis comprises investigations on the interaction of $N_2$ adsorbate molecules with size-selected iron metal clusters under cryo conditions. All investigations were performed at the customized fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer FRITZ. This setup serves a laser vaporization (LVAP) source to generate the investigated iron cluster ions. Cryo kinetic studies investigate the stepwise $N_2$ adsorption on size selected $Fe_n^+$ clusters under well-defined isothermal conditions. The adsorption behavior and the adsorption limits lead to information about the cluster structure and its reactivity. By coupling a tunable IR laser in the ICR cell, it is possible to perform cryo infrared photon dissociation (IR-PD) spectroscopy experiments. This provides information on binding motifs of the $N_2$ adsorbates and the cluster structure. Combining both methods with quantum chemical calculations via density functional theory (DFT) substantiates the experimental results and deepens the fundamental insights into the cluster structure, their reactivity, and the metal-adsorbate bonding

Cryo Kinetics of N2N_2 Adsorption to Isolated Cationic Iron Clusters and Cryo IR Spectroscopy of the N2N_2 Adsorbates

This thesis comprises investigations on the interaction of $N_2$ adsorbate molecules with size-selected iron metal clusters under cryo conditions. All investigations were performed at the customized fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer FRITZ. This setup serves a laser vaporization (LVAP) source to generate the investigated iron cluster ions. Cryo kinetic studies investigate the stepwise $N_2$ adsorption on size selected $Fe_n^+$ clusters under well-defined isothermal conditions. The adsorption behavior and the adsorption limits lead to information about the cluster structure and its reactivity. By coupling a tunable IR laser in the ICR cell, it is possible to perform cryo infrared photon dissociation (IR-PD) spectroscopy experiments. This provides information on binding motifs of the $N_2$ adsorbates and the cluster structure. Combining both methods with quantum chemical calculations via density functional theory (DFT) substantiates the experimental results and deepens the fundamental insights into the cluster structure, their reactivity, and the metal-adsorbate bonding

Cryo-IR spectroscopy and cryo-kinetics of cluster N2 adsorbate complexes of tantalum cluster cations Ta5-8+

We present an IR-PD study of tantalum cluster adsorbate complexes [Tan(N2)m]+, abbreviated (n,m), n = 5–8. We utilize infrared spectroscopy of isolated and size selected clusters as prepared and characterized by a cryogenic tandem ion trap setup, and we augment our experiments with quantum chemical simulations at the level of density functional theory. The cluster adsorbate complexes (n,m) reveal vibrational bands above 2000 cm−1, which indicate end-on coordinated μ1-N2 oscillators, and bands below 2000 cm−1, which indicate side-on μ2-κN:κN,N coordinated ones. We observe a general increase in spectral complexity and an inhomogeneous broadening, mainly towards the red, at certain points of N2 loading m, which originates from an increasingly higher amount of double and triple N2 coordination at Ta sites, eventually at all of them. Other than the small tantalum clusters Tan+, n = 2–4, the IR-PD spectra of the initial N2 adsorbate species (n,1), n = 5–8, provide strong evidence for a lack of spontaneous N2 cleavage. Spontaneous N2 cleavage by Tan+, n = 5–8, seems suppressed. Therefore, the ability of a small Ta cluster to cleave dinitrogen disappears with one more tantalum core atom. The study of stepwise N2 adsorption on size selected Tan+, n = 5–8 clusters revealed adsorption limits m(max) of [Tan(N2)m]+ that are independent of cluster size within this size range. Cryo-adsorption kinetics at 26 K allowed for kinetic fits to consecutive N2 adsorption steps, and the fits revealed significant N2 desorption rates upon higher N2 loads, and the cluster adsorbate complexes eventually reached equilibrium. Some enhanced N2 desorption rates point towards likely adsorbate shell reorganization, and there is also some evidence for the coexistence of isomeric cluster adsorbate complexes

Cryo IR spectroscopy and cryo kinetics of dinitrogen activation and cleavage by small tantalum cluster cations

We investigate small tantalum clusters Tan+, n = 2–4, for their capability to cleave N2 adsorption spontaneously. We utilize infrared photon dissociation (IR-PD) spectroscopy of isolated and size selected clusters under cryogenic conditions within a buffer gas filled ion trap, and we augment our experiments by quantum chemical simulations (at DFT level). All Tan+ clusters, n = 2–4, seem to cleave N2 efficiently. We confirm and extend a previous study under ambient conditions on Ta2+ cluster [Geng et al., Proc. Natl. Acad. Sci. U. S. A. 115, 11680–11687 (2018)]. Our cryo studies and the concomitant DFT simulations of the tantalum trimer Ta3+ suggest cleavage of the first and activation of the second and third N2 molecule across surmountable barriers and along much-involved multidimensional reaction paths. We unravel the underlying reaction processes and the intermediates involved. The study of the N2 adsorbate complexes of Ta4+ presented here extends our earlier study and previously published spectra from (4,m), m = 1–5 [Fries et al., Phys. Chem. Chem. Phys. 23(19), 11345–11354 (2021)], up to m = 12. We confirm the priory published double activation and nitride formation, succeeded by single side-on N2 coordination. Significant red shifts of IR-PD bands from these side-on coordinated μ2-κN:κN,N N2 ligands correlate with the degree of tilting towards the second coordinating Ta center. All subsequently attaching N2 adsorbates onto Ta4+ coordinate in an end-on fashion, and we find clear evidence for co-existence of end-on coordination isomers. The study of stepwise N2 adsorption revealed adsorption limits m(max) of [Tan(N2)m]+ which increase with n, and kinetic fits revealed significant N2 desorption rates upon higher N2 loads. The enhanced absolute rate constants of the very first adsorbate steps kabs(n,0) of the small Ta3+ and Ta4+ clusters independently suggest dissociative N2 adsorption and likely N2 cleavage into Ta nitrides

Cryo infrared spectroscopy of N2 adsorption onto bimetallic rhodium–iron clusters in isolation

We investigated the N2 adsorption behavior of bimetallic rhodium–iron cluster cations [RhiFej(N2)m]+ by means of InfraRed MultiplePhotoDissociation (IR-MPD) spectroscopy in comparison with density functional theory (DFT) modeling. This approach allows us to refine our kinetic results [Ehrhard et al., J. Chem. Phys. (in press)] to enhance our conclusions. We focus on a selection of cluster adsorbate complexes within the ranges of i = j = 3–8 and m = 1–10. For i = j = 3, 4, DFT suggests alloy structures in the case of i = j = 4 of high (D2d) symmetry: Rh–Fe bonds are preferred instead of Fe–Fe bonds or Rh–Rh bonds. N2 adsorption and IR-MPD studies reveal strong evidence for preferential adsorption to Rh sites and mere secondary adsorption to Fe. In some cases, we observe adsorption isomers. With the help of modeling the cluster adsorbate complex [Rh3Fe3(N2)7]+, we find clear evidence that the position of IR bands allows for an element specific assignment of an adsorption site. We transfer these findings to the [Rh4Fe4(N2)m]+ cluster adsorbate complex where the first four N2 molecules are exclusively adsorbed to the Rh atoms. The spectra of the larger adsorbates reveal N2 adsorption onto the Fe atoms. Thus, the spectroscopic findings are well interpreted for the smaller clusters in terms of computed structures, and both compare well to those of our accompanying kinetic study [Ehrhard et al., J. Chem. Phys. (in press)]. In contrast to our previous studies of bare rhodium clusters, the present investigations do not provide any indication for a spin quench in [RhiFej(N2)m]+ upon stepwise N2 adsorption

Cryo spectroscopy of N2 on cationic iron clusters

Infrared photodissociation (IR-PD) spectra of iron cluster dinitrogen adsorbate complexes [Fen(N2)m]+ for n = 8–20 reveal slightly redshifted IR active bands in the region of 2200–2340 cm−1. These bands mostly relate to stretching vibrations of end-on coordinated N2 chromophores, a μ1,end end-on binding motif. Density Functional Theory (DFT) modeling and detailed analysis of n = 13 complexes are consistent with an icosahedral Fe13+ core structure. The first adsorbate shell closure at (n,m) = (13,12)—as recognized by the accompanying paper on the kinetics of N2 uptake by cationic iron clusters—comes with extensive IR-PD band broadening resulting from enhanced couplings among adjacent N2 adsorbates. DFT modeling predicts spin quenching by N2 adsorption as evidenced by the shift of the computed spin minima among possible spin states (spin valleys). The IR-PD spectrum of (17,1) surprisingly reveals an absence of any structure but efficient non-resonant fragmentation, which might indicate some weakly bound (roaming) N2 adsorbate. The multiple and broad bands of (17,m) for all other cases than (17,1) and (17,7) indicate a high degree of variation in N2 binding motifs and couplings. In contrast, the (17,7) spectrum of six sharp bands suggests pairwise equivalent N2 adsorbates. The IR-PD spectra of (18,m) reveal additional features in the 2120–2200 cm−1 region, which we associate with a μ1,side side-on motif. Some additional features in the (18,m) spectra at high N2 loads indicate a μ1,tilt tilted end-on adsorption motif

Kinetics of stepwise nitrogen adsorption by size-selected iron cluster cations: Evidence for size-dependent nitrogen phobia

We present a study of stepwise cryogenic N2 adsorption on size-selected Fen+ (n = 8–20) clusters within a hexapole collision cell held at T = 21–28 K. The stoichiometries of the observed adsorption limits and the kinetic fits of stepwise N2 uptake reveal cluster size-dependent variations that characterize four structural regions. Exploratory density functional theory studies support tentative structural assignment in terms of icosahedral, hexagonal antiprismatic, and closely packed structural motifs. There are three particularly noteworthy cases, Fe13+ with a peculiar metastable adsorption limit, Fe17+ with unprecedented nitrogen phobia (inefficient N2 adsorption), and Fe18+ with an isomeric mixture that undergoes relaxation upon considerable N2 uptake

Hospital Admission and Discharge: Lessons Learned from a Large Programme in Southwest Germany

Introduction: In the context of a GP-based care programme, we implemented an admission, discharge and follow-up programme. Description: The VESPEERA programme consists of three sets of components: pre-admission interventions, in-hospital interventions and post-discharge interventions. It was aimed at all patients with a hospital stay participating in the GP-based care programme and was implemented in 7 hospitals and 72 general practices in southwest Germany using a range of strategies. Its’ effectiveness was evaluated using readmissions within 90 days after discharge as primary outcome. Questionnaires with staff were used to explore the implementation process. Discussion: A statistically significant effect was not found, but the effect size was similar to other interventions. Intervention fidelity was low and contextual factors affecting the implementation, amongst others, were available resources, external requirements such as legal regulations and networking between care providers. Lessons learned were derived that can aid to inform future political or scientific initiatives. Conclusion: Structured information transfer at hospital admission and discharge makes sense but the added value in the context of a GP-based programme seems modest. Primary care teams should be involved in pre- and post-hospital care. Abstrakt Einleitung: Im Rahmen der hausarztzentrierten Versorgung wurde ein Programm zur Verbesserung von Krankenhausaufnahmen und -entlassungen sowie der Nachsorge implementiert. Beschreibung: Das VESPEERA-Programm bestand aus verschiedenen Komponenten, die vor der Aufnahme, während des Krankenhausaufenthalts sowie nach der Entlassung durchgeführt wurden. Das Programm richtete sich an alle Patienten mit einem Krankenhausaufenthalt, die an der hausarztzentrierten Versorgung teilnahmen und wurde in 7 Krankenhäusern und 72 Hausarztpraxen in Südwestdeutschland unter Anwendung einer Reihe von Strategien implementiert. Seine Wirksamkeit wurde anhand des primären Endpunkts “Rehospitalisierungen innerhalb von 90 Tagen nach der Entlassung” bewertet. Anhand einer Fragebogenbefragung beim Personal wurde der Implementierungsprozess untersucht. Diskussion: Ein statistisch signifikanter Effekt konnte nicht gefunden werden, die Effektgröße war jedoch ähnlich wie bei anderen Interventionen. Die Interventionstreue war gering. Kontextfaktoren, die die Implementierung beeinflussten, waren unter anderem verfügbare Ressourcen, externe Anforderungen wie gesetzliche Vorschriften und die Vernetzung von Leistungserbringern. Es wurden Schlussfolgerungen gezogen, die für künftige politische oder wissenschaftliche Initiativen hilfreich sein können. Schlussfolgerung: Eine strukturierte Informationsweitergabe bei der Aufnahme und Entlassung aus dem Krankenhaus ist sinnvoll, doch scheint der zusätzliche Nutzen im Rahmen der hausarztzentrierten Versorgung begrenzt. Teams der Primärversorgung sollten in die prä- und poststationäre Versorgung einbezogen werden. Schlagwörter: Übergänge in der Versorgung; Einweisungsmanagement; Nachsorge nach Entlassung; Krankenhauswiederaufnahmen; Versorgungskontinuität; starke Primärversorgung; integrierte Versorgun