Two heads are better than one:improving magnetic relaxation in the dysprosium metallocene DyCp*₂BPh₄ upon dimerization by use of an exceptionally weakly-coordinating anion

Abstract Partial metathesis between two weakly-coordinating anions in the archetypical dysprosium metallocene DyCp*₂BPh₄ results in the first example of [BPh₄]⁻ as a bridging ligand in 4f metals, with a unique η₂,η₂:η₂,η₂-bridge. Magnetic susceptibility and relaxation dynamics studies along with ab initio calculations reveal improved slow relaxation of the magnetization in [Dy₂Cp*₄(μ-BPh₄)][Al(OC(CF₃)₃)₄] over its mononuclear congener, resulting in an energy barrier of 490 K/340 cm⁻¹ and waist-restricted hysteresis up to 6.5 K

Harnessing the Synergy between Upconverting Nanoparticles and Lanthanide Complexes in a Multiwavelength-Responsive Hybrid System

We prepared a hybrid system composed of a continuous film of a dinuclear lanthanide complex [Ln(2) bpm(tfaa)(6)] (Ln = Tb or Eu) and upconverting nanoparticles (UCNPs) using a straightforward drop-cast methodology. The system displayed visible emission under near-infrared (NIR) excitation, simultaneously stemming from sub-10 nm UCNPs and [Ln(2)] complexes, the latter species being otherwise directly excitable only using UV-blue radiation. In light of the results of steady-state including power-dependent and time-resolved optical measurements, we identified the radiative, primarily ligand-mediated nature of the energy transfer from Tm3+ ions in the UCNPs to Ln(3+) ions in the complexes. Hyperspectral mapping and electron microscopy observations of the surface of the hybrid system confirmed the continuous and concomitant distribution of UCNPs and lanthanide complexes over the extensive composite films. Key features of the hybrid system are the simultaneous UV-blue and NIR light harvesting capabilities and their ease of preparation. These traits render the presented hybrid system a formidable candidate for the development of photoactivated devices capable of operating under multiple excitation wavelengths and to transduce the absorbed light into narrow, well-defined spectral regions

Oxygen-17 NMR Spectroscopy of Water Molecules in Solid Hydrates

Oxygen-17 solid-state NMR studies of waters of hydration in crystalline solids are presented. The 17O quadrupolar coupling and chemical shift (CS) tensors, and their relative orientations, are measured experimentally at room temperature for ď Ą-oxalic acid dihydrate, barium chlorate monohydrate, lithium sulfate monohydrate, potassium oxalate monohydrate, and sodium perchlorate monohydrate. The 17O quadrupolar coupling constants (CQ) range from 6.6 to 7.35 MHz and the isotropic chemical shifts range from -17 to 19.7 ppm. The oxygen CS tensor spans vary from 25 to 78 ppm. These represent the first complete CS and electric field gradient tensor measurements for water coordinated to metals in the solid state. Gauge-including projector-augmented wave density functional theory calculations overestimate the values of CQ, likely due to librational dynamics of the water molecules. Computed CS tensors only qualitatively match the experimental data. The lack of strong correlations between the experimental and computed data, and between these data and any single structural feature is attributed to motion of the water molecules and to the relatively small overall range in the NMR parameters relative to their measurement precision. Nevertheless, the isotropic chemical shift, quadrupolar coupling constant, and CS tensor span clearly differentiate between the samples studied, and establish a â fingerprintâ 17O spectral region for water coordinated to metals in solids.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Radical bridged Ln₄ metallocene complexes with strong magnetic coupling and large coercive field

Abstract Inducing magnetic coupling between 4f elements is an ongoing challenge. To overcome this formidable difficulty, we incorporate highly delocalized tetrazinyl radicals, which strongly couple with f-block metallocenes to form discrete tetranuclear complexes. Synthesis, structure, magnetic properties of two tetranuclear [(Cp*₂Ln)₄(tz•)₄]·3(C₆H₆) (Cp* = pentamethylcyclopentadienyl; tz = 1,2,4,5-tetrazine; Ln = Dy, Gd) complexes are reported. An in-depth examination of their magnetic properties through magnetic susceptibility measurements, as well as computational studies, support a highly sought-after radical-induced “giant-spin” model. Strong exchange interactions between the LnIII ions and tz• radicals lead to a strong magnet-like behaviour in this molecular magnet with a giant coercive field of 30 kOe

Aufbau vs. non-Aufbau ground states in two-coordinate d⁷ single-molecule magnets

Abstract Single-molecule magnets (SMMs) with d⁷ electronic configurations often require designer ligands to satisfy the metals electronic conditions to achieve large angular momentum. Herein, the slow relaxation of the magnetization in two d⁷ metal complexes in near identical ligand fields is achieved from divergent origins. The two compounds, [CoII{N(SiMePh₂)₂}₂] and [K(2,2,2-crypt)][FeI{N(SiMePh₂)₂}₂] (2,2,2-crypt = 2,2,2-cryptand), display unusual electronic configurations giving rise to SMM behavior originating either from 3d–4s orbital mixing or a non-Aufbau ground state. The chracteristics contributing to the rare non-Aufbau ground state configurations are illuminated by the use of a highly donating amido-ligand, which would be expected to significantly split the respective orbitals. Magnetic circular dichroism provides experimental support for ab initio determined electronic structures. Moreover, computational models reveal that the relative electronic configurations are largely retained independently of coordination geometry, provided that some degree of pseudo-linearity is retained. Thus, providing generalized design principles in the pursuit of linear d⁷ SMMs

A Luminescent Thermometer Exhibiting Slow Relaxation of the Magnetization : Toward Self-Monitored Building Blocks for Next-Generation Optomagnetic Devices

The development and integration of Single-Molecule Magnets (SMMs) into molecular electronic devices continue to be an exciting challenge. In such potential devices, heat generation due to the electric current is a critical issue that has to be considered upon device fabrication. To read out accurately the temperature at the submicrometer spatial range, new multifunctional SMMs need to be developed. Herein, we present the first self-calibrated molecular thermometer with SMM properties, which provides an elegant avenue to address these issues. The employment of 2,2′-bipyrimidine and 1,1,1-trifluoroacetylacetonate ligands results in a dinuclear compound, [Dy2(bpm)(tfaa)6], which exhibits slow relaxation of the magnetization along with remarkable photoluminescent properties. This combination allows the gaining of fundamental insight in the electronic properties of the compound and investigation of optomagnetic cross-effects (Zeeman effect). Importantly, spectral variations stemming from two distinct thermal-dependent mechanisms taking place at the molecular level are used to perform luminescence thermometry over the 5–398 K temperature range. Overall, these properties make the proposed system a unique molecular luminescent thermometer bearing SMM properties, which preserves its temperature self-monitoring capability even under applied magnetic fields.peerReviewe

Triplet-State Position and Crystal-Field Tuning in Opto‐Magnetic Lanthanide Complexes : Two Sides of the Same Coin

Lanthanide complex‐based luminescence thermometry and single‐molecule magnetism are two effervescent research fields, owing to the great promise they hold from an application standpoint. The high thermal sensitivity achievable, their contactless nature, along with sub‐micrometric spatial resolution make these luminescent thermometers appealing for accurate temperature probing in miniaturized electronics. To that end, single‐molecule magnets (SMMs) are expected to revolutionize the field of spintronics, thanks to the improvements made in terms of their working temperature – now surpassing that of liquid nitrogen – and manipulation of their spin state. Hence, the combination of such opto‐magnetic properties in a single molecule is desirable in the aim of overcoming, among others, addressability issues. Yet, improvements have to be made through design strategies for the realization of the aforementioned goal. Moving forward from these considerations, we present a thorough investigation of the effect that changes in the ligand scaffold of a family of terbium complexes have on their performance as luminescent thermometers and SMMs. In particular, an increased number of electron withdrawing groups yields modifications of the metal coordination environment and a lowering of the triplet state of the ligands. These effects are tightly intertwined, thus, resulting in concomitant variations of the SMM and the luminescence thermometry behaviour of the complexes.peerReviewe