Abstract The determination of the orientations of the individual DyIII anisotropy axes in polynuclear complexes is challenging but crucial for the understanding of systems showing Single Molecule Magnet or Single Molecule Toroic behavior. In particular, the experimental proof of a toroidal ground state from magnetization data often remains ambiguous. Here, we report the coordination cluster [CoIII 3DyIII 3(µ3-OH)4(O2C-C6H4-p-Me)6(pmide)3(H2O)3]Cl2 · 10MeCN (1) (H2pmide = N-2-pyridylmethyldiethanolamine) which crystallizes with threefold symmetry and contains an equilateral DyIII 3 triangle surrounded by a triangle of diamagnetic CoIII ions. We also report a multi-technique investigation of its toroidal magnetic spin structure, including 161Dy Synchrotron Mössbauer Spectroscopy which shows an abrupt transition from a non-magnetic to a magnetic state. The experimental orientations of the individual DyIII magnetic axes were assessed using torque magnetometry and micro-SQUID measurements and both experiments converged on a spin structure that is in very good agreement with ab initio calculations. Such a multi-technique approach, including 161Dy Synchrotron Mössbauer Spectroscopy, provides a roadmap for the unambiguous identification of such toroidal states.

The nitrophorins (NPs) comprise an unusual group of heme proteins with stable ferric heme iron nitric oxide (Fe-NO) complexes. They are found in the salivary glands of the blood-sucking kissing bug Rhodnius prolixus, which uses the NPs to transport the highly reactive signaling molecule NO. Nuclear resonance vibrational spectroscopy (NRVS) of both isoform NP2 and a mutant NP2(Leu132Val) show, after addition of NO, a strong structured vibrational band at around 600 cm-1, which is due to modes with significant Fe-NO bending and stretching contribution. Based on a hybrid calculation method, which uses density functional theory and molecular mechanics, it is demonstrated that protonation of the heme carboxyl groups does influence both the vibrational properties of the Fe-NO entity and its electronic ground state. Moreover, heme protonation causes a significant increase of the gap between the highest occupied and lowest unoccupied molecular orbital by almost one order of magnitude leading to a stabilization of the Fe-NO bond.

Within this work, we report the results of nuclear inelastic scattering experiments of the low-spin phase of the iron(II) mononuclear SCO complex Fe[HBpz 3 ] 2 and density functional theory based calculations performed on a model molecule of the complex. We show that the calculated partial density of vibrational states based on the structure of a single iron(II) center which is linked by three pyrazole rings to borat is in good accordance with the experimentally obtained 57 Fe-pDOS and assign the molecular vibrations to the prominent optical phonons.

The article was published with erroneous values in Table 1. Please find in this document the correct version of Table 1 that should be regarded as the final version by the reader

Synchrotron-based nuclear resonance vibrational spectroscopy (NRVS) using the Mossbauer isotope Dy-161 has been employed for the first time to study the vibrational properties of a single-molecule magnet (SMM) incorporating Dy-III, namely [Dy(Cy3PO)(2)(H2O)(5)]Br-3.2 (Cy3PO).2 H2O .2 EtOH. The experimental partial phonon density of states (pDOS), which includes all vibrational modes involving a displacement of the Dy-III ion, was reproduced by means of simulations using density functional theory (DFT), enabling the assignment of all intramolecular vibrational modes. This study proves that Dy-161 NRVS is a powerful experimental tool with significant potential to help to clarify the role of phonons in SMMs.

AbstractErstmalig wurde Synchrotron‐basierte nukleare inelastische Streuung (NIS) unter Nutzung des Mößbauer‐Isotops 161Dy für die Untersuchung der vibronischen Eigenschaften eines DyIII‐basierten Einzelmolekülmagneten, [Dy(Cy3PO)2(H2O)5]Br3⋅2 (Cy3PO)⋅2 H2O⋅2 EtOH, eingesetzt. Die experimentelle partielle Phononen‐Zustandsdichte, die alle Schwingungen mit einer Auslenkung des DyIII‐Ions enthält, wurde mit Hilfe von auf Dichtefunktionaltheorie (DFT) basierenden Simulationen reproduziert, was die Zuordnung aller intramolekularen Schwingungsmoden des Moleküls ermöglicht. Diese Studie zeigt, dass 161Dy‐NIS als eine experimentelle Methode ein hohes Potential besitzt, um zur Klärung der Rolle von Phononen in Einzelmolekülmagneten beizutragen.

The vibronic properties of two dimeric iron (II) high-spin complexes [5CpFeX]2 (5Cp = Pentaisopropyl-cyclopentadienyl, X = OH-(1), Br-(2)) have been studied using nuclear inelastic scattering (NIS). In order to assign the experimentally observed bands to the particular modes, theoretical calculations using density functional theory (DFT) have been performed based on the structural data obtained by X-ray crystallography. The calculated partial density of vibrational states (pDOS) reproduces the experimental data. Thus, we were able to assign almost each of the experimentally observed NIS bands to their corresponding molecular vibrational modes.

Angewandte ChemieVolume 132, Issue 23 p. 8813-8832 Graphisches InhaltsverzeichnisFree Access Graphisches Inhaltsverzeichnis: Angew. Chem. 23/2020 First published: 25 May 2020 https://doi.org/10.1002/ange.202082311AboutPDF ToolsRequest permissionAdd to favorites ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume132, Issue23June 2, 2020Pages 8813-8832 This is the German version of Angewandte Chemie. Note for articles published since 1962: Do not cite this version alone. Take me to the International Edition version with citable page numbers, DOI, and citation export. We apologize for the inconvenience. RelatedInformation

The vibrational dynamics of the iron centres in 1D and 3D spin crossover Fe(II) 4-alkyl-urea triazole chains have been investigated by synchrotron based nuclear inelastic scattering. For the 1D system, the partial density of phonon states has been modelled with density functional theory methods. Furthermore, spin dependent iron ligand distances and vibrational modes were obtained. The previously introduced intramolecular cooperativity parameter H-coop (Rackwitz et al, Phys. Chem. Chem. Phys. 2013, 15, 15450) has been determined to -31 kJ mol(-1) for [Fe(n-Prtrzu)(3)(tosylate)(2)] and to +27 kJ mol(-1) for [Fe(n-Prtrzu)(3)(BF4)(2)]. The change of sign in H-coop is in line with the incomplete and gradual character of the spin transition for the former as well as with the sharp transition for the latter reported previously (Rentschler and von Malotki, Inorg. Chem., Act. 2008, 361, 3646). This effect can be ascribed to the networks of intramolecular interactions in the second coordination sphere of the polymer chains, depending on the spin state of the iron centres. In addition, we observe a decreased coupling and coherence when comparing the system which displays a sharp spin transition to the system with an incomplete soft transition by analyzing molecular modes involving a movement of the iron centres.

AbstractFe–N–C catalysts are very promising materials for fuel cells and metal–air batteries. This work gives fundamental insights into the structural composition of an Fe–N–C catalyst and highlights the importance of an in‐depth characterization. By nuclear‐ and electron‐resonance techniques, we are able to show that even after mild pyrolysis and acid leaching, the catalyst contains considerable fractions of α‐iron and, surprisingly, iron oxide. Our work makes it questionable to what extent FeN4 sites can be present in Fe–N–C catalysts prepared by pyrolysis at 900 °C and above. The simulation of the iron partial density of phonon states enables the identification of three FeN4 species in our catalyst, one of them comprising a sixfold coordination with end‐on bonded oxygen as one of the axial ligands.

AbstractTime‐domain synchrotron Mössbauer spectroscopy (SMS) based on the Mössbauer effect of 161Dy has been used to investigate the magnetic properties of a DyIII‐based single‐molecule magnet (SMM). The magnetic hyperfine field of [Dy(Cy3PO)2(H2O)5]Br3⋅2 (Cy3PO)⋅2 H2O⋅2 EtOH is with B0=582.3(5) T significantly larger than that of the free‐ion DyIII with a 6H15/2 ground state. This difference is attributed to the influence of the coordinating ligands on the Fermi contact interaction between the s and 4f electrons of the DyIII ion. This study demonstrates that 161Dy SMS is an effective local probe of the influence of the coordinating ligands on the magnetic structure of Dy‐containing compounds.

Iron(II) spin crossover complexes display a reversible transition from low-spin (LS) state to high-spin (HS) state by e.g. variation of temperature, pressure or by irradiation with light. Therefore, these systems are promising candidates for information storage materials. In view of practical device applications thin films of these materials are needed. The SCO-compound [Fe(Htrz)2(trz)] (BF4) (1) switches between the LS and the HS state with a 50 K wide thermal hysteresis loop above room temperature. We have prepared thin films of 1 on a SiO2 substrate by spin coating. The spin states of the films have been characterized by Mössbauer spectroscopy in reflection mode using a MIMOS II spectrometer. A low quadrupole splitting (LS state) at 300 K and a high quadrupole splitting (HS state) at 400 K were found for the film, as well as for bulk powder of 1. This confirms that a spin crossover occurs above room temperature. Furthermore, synchrotron based nuclear resonance scattering measurements from 80 K to 400 K indicate that the hyperfine parameters are similar to those of the bulk powder of 1. DFT calculations reproduce the experimentally determined Fe-vibrational density of states of the bulk and of the thin film sample of 1. These results indicate that a higher fraction of HS Fe atoms is present in the film of 1. Therefore, we conclude different SCO properties of the thin film and the bulk material of 1.

Apd1,a cytosolic yeast protein, and Aim32, its counterpart in the mitochondrialmatrix, have a C-terminal thioredoxinlike ferredoxin domain and a widelydivergent N-terminal domain. These proteins are found in bacteria, plants,fungi and unicellular pathogenic eukaryotes, but not in Metazoa. Ourchemogenetic experiments demonstrate that the highly conserved cysteine andhistidine residues within the C-X8-C-X24-75-H-X-G-G-H motif of the TLF domainof Apd1 and Aim32 proteins are essential for viability upon treatment of yeastcells with the redox potentiators gallobenzophenone or pyrogallol,respectively. UV-Vis, EPR and Mössbauer spectroscopy of purified wild type Apd1and three His to Cys variants demonstrated that Cys207 and Cys216 are theligands of the ferric ion and His255 and His259 are the ligands of thereducible iron ion of the [2Fe-2S]2+/1+ cluster. The [2Fe-2S] center of Apd1(Em,7 = -164±5 mV, pKox1,2=7.9±0.1 and 9.7±0.1) differs from both dioxygenase(Em,7 ≈ -150 mV, pKox1,2=9.8 and 11.5) and cytochromebc1/b6f Rieske clusters (Em,7 ≈+300 mV, pKox1,2= 7.7 and 9.8). Apd1 and its engineered variants represent anunprecedented flexible system for which a stable [2Fe-2S] cluster with twohistidine ligands, (two different) single histidine ligands or only cysteinylligands is possible in the same protein fold. Our results define a remarkableexample of convergent evolution of [2Fe-2S] cluster containing proteins withbis-histidinyl coordination and proton-coupled electron transfer.

Einzelmolekülmagnete lassen sich mit 161Dy-Zeitdomänen-Mößbauer-Spektroskopie analysieren. In ihrer Zuschrift auf S. 3482 beschreiben L. Scherthan, A. K. Powell, V. Schünemann und Mitarbeiter, wie anhand des 161Dy-Kerns die magnetischen Eigenschaften Dy-haltiger Verbindungen ermittelt werden können – direkt aus der Sicht des Lanthanoidions.

161 Dy time-domain synchrotron Mössbauer spectroscopy (SMS), just recently presented as a novel tool to investigate Dy(III)-based single-molecule magnets (SMMs), has now been applied on two polynuclear Dy 6 -based wheel compounds possessing special features of single-molecule toroics (SMTs). The magnitude of the magnetic hyperfine field revealed for the Dy 6 ring system [Dy 6 (teaH) 6 (NO 3 ) 6 ]·8MeOH is with B 0 = 574.3(5) T characteristic for Dy(III) with a 6 H 15/2 ground state. The ligand substituted compound [Dy 6 (Me-teaH) 6 (NO 3 ) 6 ]·6MeCN possesses within the experimental errors the same magnetic hyperfine characteristics ( B 0 = 574.9(5) T). Consequently, the herein studied organic ligand variation has no perceptible influence on the magnetic hyperfine field sensed by the 161 Dy(III) nuclei in these particular homometallic Dy(III) 6 -wheels.

Single-molecule magnets can be investigated by means of 161Dy time-domain Mössbauer spectroscopy. In their Communication on page 3444 ff., L. Scherthan, A. K. Powell, V. Schünemann, and co-workers report how the 161Dy nucleus can be used to probe the magnetic properties of Dy-containing compounds directly from the viewpoint of the lanthanide ions.

The partial density of vibrational states (pDOS) of the low-spin isomer of the tosylate salt of [Fe{(N-Propyl)-N′-(1,2,4-triazole-4-yl-urea)}3]2+ was determined by nuclear inelastic scattering experiments performed at 8 K. The pDOS features a rich band structure from 320 to 500 cm−1, characteristic of the low spin state of the complex. Density functional theory calculations (B3LYP/CEP-31G) were used to assign molecular modes to the experimentally observed peak in the pDOS.