Jakob K. Staab

The reactions of ytterbium(III) bromide or iodide with the N3O2 Schiff base 2,6-bis(2-hydroxyphenyliminomethyl)pyridine (H2L) afford the complexes [Yb(L)Br(CH3CH2OH)]·CH3OH (1·CH3OH) and [Yb(L)(H2O)3]I·CH3CH2OH·H2O (2·CH3CH2OH·H2O), respectively, as single crystals. X-ray diffraction reveals markedly different geometries around the Yb3+ ions. Thus, 1 features a seven-coordinate pentagonal-bipyramidal arrangement, whereas 2 exhibits a triangular dodecahedral environment. Magnetic studies indicate that both compounds exhibit field-induced single-ion magnet (SIM) behavior, with magnetization relaxation governed by quantum tunneling of the magnetization (QTM) and Raman processes. Furthermore, temperature-dependent luminescence measurements demonstrate that both complexes can function as nanoscale luminescent thermometers, resulting in bifunctional magnetic–thermometric molecular materials. Notably, the auxiliary ligands exert a pronounced influence on the thermometric performance while only moderately affecting the magnetic behavior. Complex 1 displays superior thermometric properties, reaching a relative sensitivity of 3.7% K–1 at 60 K, which represents the highest value reported to date for mononuclear Yb3+ field-induced single-ion magnets, together with a minimum temperature uncertainty of 0.2 K. Ab initio calculations provide a theoretical interpretation of both the observed magnetic relaxation dynamics and the luminescence properties.

Here, we investigate the magnetic exchange coupling and magnetic anisotropy of a Co(II)–Cu(II) complex using ab initio multiconfigurational calculations. This is one of the simplest cases of magnetic exchange coupling involving an orbitally degenerate metal center: a pseudo-octahedral 3d7 Co(II) ion and a spin-only 3d9 Cu(II) ion. Electronic structure calculations were performed using CASSCF and CASPT2/NEVPT2 methods, and the resulting electronic states were further analyzed via model Hamiltonians to extract physically meaningful parameters, including crystal field splitting, spin–orbit coupling, and exchange coupling. The CASPT2/NEVPT2 calculations improved the agreement with experiment compared to that of CASSCF by correcting the overestimation of ferromagnetic coupling. Our calculations highlight that spin–orbit exchange coupling (i.e., spin-other-orbit coupling) is just as important as spin–spin exchange coupling for an accurate description of exchange coupling.

Mixed-valence complexes featuring lanthanide-lanthanide bonding have recently been shown to act as single-molecule magnets with unprecedented operating temperatures and magnetic coercivities. Here, we present the synthesis and detailed examination of the electronic structure, bonding, and magnetic properties of mixed-valence trinuclear clusters (C₅ⁱPr₅)₃Ln₃H₃I₂ (Ln = Tb, Dy, Ho, Er, and Tm). Near-infrared and X-ray absorption spectra, together with computational results, confirm these clusters possess a three-center, one-electron σ bond. This metal-metal bonding leads to strong intermetal exchange coupling, resulting in magnetic behaviors that starkly contrast with typical multinuclear lanthanide complexes. Notably, structural, spectroscopic, and computational studies of the thulium cluster reveal valence delocalization through a bonding orbital of 5d-parentage between the three Tm centers. This observation represents the first example of a nontraditional electronic structure for thulium involving 5d rather than 4f orbitals. Magnetic analysis reveals a complex interplay between single-ion magnetic anisotropy and ferromagnetic exchange, governing the overall magnetic anisotropy of these clusters. Magnetic susceptibility measurements for Ln = Tb-Er indicate thermally well-isolated high-moment ground states arising from strong magnetic coupling, although the maximum values are lower than those expected for complete parallel alignment of the σ and 4f electrons. Computational analyses suggest that collinear alignment of the local anisotropy axes results in out-of-plane anisotropy for Ln = Er and Tm, whereas noncollinear alignment induces in-plane anisotropy for Ln = Tb, Dy, leading to distinct magnetic relaxation properties. Together, the results highlight the diverse magnetic behaviors that can be realized through lanthanide-lanthanide bonding and outline a synthetic path forward toward maximizing the magnetic anisotropy in f-element clusters.

The trihydrogen cation, H ₃ ⁺ , is unique in the Universe. One of the features that enable its uniqueness is an antiaromatic destabilization in its lowest electronically excited states.

Calculation of phonons, phonon scattering, spin–phonon coupling and magnetic relaxation rates for a dysprosocenium single-molecule magnet show that strong scattering of low-energy modes is a significant contribution to their high-performance.

Generic frozen solution embedding enables the ab initio prediction of condensed-phase spin-dynamics under realistic conditions for molecules without crystal structures, giving insight into the impact of intramolecular bridging on magnetic relaxation.

Electron–phonon coupling is important in many physical phenomena, e.g. photosynthesis, catalysis and quantum information processing, but its impacts are difficult to grasp on the microscopic level. One area attracting wide interest is that of single-molecule magnets, which is motivated by searching for the ultimate limit in the miniaturisation of binary data storage media. The utility of a molecule to store magnetic information is quantified by the timescale of its magnetic reversal processes, also known as magnetic relaxation, which is limited by spin–phonon coupling. Several recent accomplishments of synthetic organometallic chemistry have led to the observation of molecular magnetic memory effects at temperatures above that of liquid nitrogen. These discoveries have highlighted how far chemical design strategies for maximising magnetic anisotropy have come, but have also highlighted the need to characterise the complex interplay between phonons and molecular spin states. The crucial step is to make a link between magnetic relaxation and chemical motifs, and so be able to produce design criteria to extend molecular magnetic memory. The basic physics associated with spin–phonon coupling and magnetic relaxation was outlined in the early 20th century using perturbation theory, and has more recently been recast in the form of a general open quantum systems formalism and tackled with different levels of approximations. It is the purpose of this Tutorial Review to introduce the topics of phonons, molecular spin–phonon coupling, and magnetic relaxation, and to outline the relevant theories in connection with both the traditional perturbative texts and the more modern open quantum systems methods.

In this article the recent developments of the open-source OpenMolcas chemistry software environment, since spring 2020, are described, with the main focus on novel functionalities that are accessible in the stable branch of the package and/or via interfaces with other packages. These community developments span a wide range of topics in computational chemistry, and are presented in thematic sections associated with electronic structure theory, electronic spectroscopy simulations, analytic gradients and molecular structure optimizations, ab initio molecular dynamics, and other new features. This report represents a useful summary of these developments, and it offers a solid overview of the chemical phenomena and processes that OpenMolcas can address, while showing that OpenMolcas is an attractive platform for state-of-the-art atomistic computer simulations.