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Angle-dependent high-field electron-paramagnetic-resonance data collected for single-crystal samples of Mn12-Ac is reported. None of the fine structures seen for Mn12-Ac are found for the recently discovered Mn12 complexes, thus confirming that the solvent significantly influences the magnetization dynamics in Mn12-Ac.

In this work we report a modified one-pot thermal decomposition method for the synthesis of NaLnF4 nanoparticles (Ln = Gd, Yb). This modified method allows fine-tuning of the α and β crystalline phases for both light (Gd) and heavy (Yb) lanthanides and also an easy route to the hierarchical nanostructuration of nanoparticles. The core@shell nanostructuration obtained via a step-by-step addition of the shell precursor was demonstrated by HRTEM and STEM/EDS analysis and it greatly improves the upconversion luminescence intensity of the nanoparticles. Under NIR irradiation, the visible Er3+ emission shows high thermal sensitivity in the temperature range of 83 to 323 K, reaching 9.52% K−1 at 83 K for the β-NaGd0.94Pr0.02Er0.02Yb0.02F4@3NaY0.8Yb0.2F4 sample. This is one of the highest values reported so far for upconversion thermal sensing using NaLnF4 nanoparticles. We report for the first time, a comparison between the magnetic properties of α and β-NaGdF4:Pr:Er:Yb nanoparticles. This comparison shows that the α-NaLnF4 samples systematically presented higher magnetization values than the β-NaLnF4. Our work provides a controlled method of synthesis that resulted in NaLnF4 nanoparticles with a high sensitivity for nanothermometry applications at low temperatures. The observed dependence of the magnetic properties on the crystalline phase demonstrated here clearly shows that further studies on the magnetic properties of these fluorides should be encouraged. [ABSTRACT FROM AUTHOR]

We report angle-dependent high-field electron-paramagnetic-resonance data collected for single-crystal samples of Mn12-Ac. The spectra reveal fine structures associated with various Mn12 species corresponding to different disordered local environments. Each of the fine structures exhibits a distinct dependence on the field orientation, thereby highlighting the discrete nature of the disorder. We compare these data with the spectra obtained for two recently discovered analogs of Mn12-Ac, differing only in their ligand and solvent molecules. None of the fine structures seen for Mn12-Ac are found for the recently discovered Mn12 complexes, thus confirming that the solvent significantly influences the magnetization dynamics in Mn12-Ac. [ABSTRACT FROM AUTHOR]

Two analogous tetranuclear lanthanide complexes have been synthesized with the general formula [Ln4(vht)4(MeOH)8](NO3)4·aMeOH·bH2O, where H2vht = (3,6-bis(vanillidenehydrazinyl)-1,2,4,5-tetrazine) and Ln = DyIII (1), GdIII (2). These complexes are characterized by several techniques; including single-crystal X-ray diffraction, SQUID magnetometry and single-crystal micro-SQUID hysteresis loop measurements. Elucidation of the crystal structure of the complexes shows that the lanthanide ions are bridged by a tetrazine ring, a rare bridging moiety for lanthanide ions. Magnetic studies reveal that both 1 and 2 exhibit weak ferromagnetic exchange interactions between Ln ions, and 1 displaying Single-Molecule Magnet (SMM) behaviour with a magnetisation reversal barrier of Ueff = 158 K (τ0 = 1.06 × 10−7 s). [ABSTRACT FROM AUTHOR]

A family of three dinuclear dysprosium complexes have been successfully synthesized and studied in terms of their magnetic properties. Complexes 1 and 2 share the formula [Dy2(ovph)2Cl2(solvent)2], where H2ovph = pyridine-2-carboxylic acid [(2-hydroxy-3-methoxyphenyl)methylene] hydrazide, and solvent = DMF (1), i-PrOH (2), while complex 3, [Dy2(ovph)2Cl2(H2O)3(EtOH)], exhibits differences in terms of the identity and number of coordinated solvent molecules. Thus, we investigate the impact of terminally bonded solvent molecules on the slow relaxation dynamics of {Dy2} SMMs, a parameter which can sometimes be overlooked in the quest to attain higher energy barriers. Notably, the exchange of DMF for i-PrOH, both of which coordinate through a single oxygen atom, results in a near 2-fold increase in Ueff, from 58 to 98 K, for 1 and 2, respectively. [ABSTRACT FROM AUTHOR]

Lanthanide luminescent complexes are active and thriving in various research fields due to their unique optical properties, while optical materials across a wide spectral range and with multiple functions in one were rarely reported. In this work, a new class of Ln 3+ /Al 3+ metallacrowns (MCs) were constructed with excellent luminescence properties in both the visible and near-infrared regions, and the elaborate luminescence modulation can be achieved by doping with different Ln 3+ ions. Strikingly, the powder of LnMC was developed as a luminescent nanomaterial for the detection of latent fingerprints (LFPs), and even the third level details of fingerprints can be clearly recognized, which provides a reference for the identification of fingerprints in the field of criminal investigation. More importantly, TbMC and Tb 0.1 Sm 0.9 MC can be successfully used as luminescent thermometers with sensitivities of 2.51% °C -1 and 2.33% °C -1 , respectively, higher than most reported values. Meanwhile, TbMC was developed as a luminescent probe for Fe 3+ and 2,6-pyridinedicarboxylic acid (DPA) with low limits of detection (LOD) of 0.51 μM and 4.26 μM, respectively, representing the first example of MC with luminescence sensing. Also of note is that SmMC, Tb 0.1 Sm 0.9 MC and TbMC can be functionalized as luminescent inks and films due to their clear recognizable colours in the visible range, suggesting a new strategy for high-level anti-counterfeiting. In short, the LnMC luminescent material has wide application prospects in many fields, especially rare for multifunctional applications of small-molecule complexes with non-metal-organic frameworks., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Solar-driven hydrogen production is regarded as one of the most ideal methods to achieve a sustainable society. In order to artificially establish efficient photosynthetic systems, efforts have been made to develop single-molecular photocatalysts capable of serving both as a photosensitizer (PS) and a catalyst (Cat) in hydrogen evolution reaction (HER). Although examples of such hybrid molecular photocatalysts have been demonstrated in the literature, their solar energy conversion efficiencies still remain quite limited. Here we demonstrate that a new dinuclear platinum(II) complex Pt 2 (bpia)Cl 3 (bpia=bis(2-pyridylimidoyl)amido) serves as a single-molecular photocatalyst for HER with its performance significantly higher than that of the PtCl(tpy)- and PtCl 2 (bpy)-type photocatalysts developed in our group (tpy=2,2':6',2''-terpyridine, bpy=2,2'-bipyridine). The outstanding feature is that Pt 2 (bpia)Cl 3 can produce H 2 even by irradiating the lower-energy light above 500 nm, which is rationalized due to the direct population of triplet states via singlet-to-triplet transitions (i.e., S-T transitions) accelerated by the diplatinum core. To the best of our knowledge, Pt 2 (bpia)Cl 3 is the first example of a single-molecular photocatalyst enabling hydrogen production from water via the S-T transitions using lower-energy light (>580 nm)., (© 2025 Wiley-VCH GmbH.)

Competing Interests: Competing interests: The authors declare no competing interests.

The magnetic and magneto-optical properties of a tetrazinyl radical-bridged Er III metallocene, [(Cp* 2 Er III ) 2 (bpytz •- )][BPh 4 ] ( 1 ; Cp* = pentamethylcyclopentadienyl, bpytz = 3,6-bis(3,5-dimethyl-pyrazolyl)-1,2,4,5-tetrazine), are reported. As confirmed by these studies strong Ln-rad coupling is achieved, with 1 exhibiting slow magnetic relaxation under a 1000 Oe dc field. The optical and magneto-optical profile of 1 is completed by both near-infrared (NIR) luminescence and magnetic circularly polarized luminescence (MCPL), representing the first example of NIR MCPL with Er III .

Lanthanide-based Single-Molecule Magnets (SMMs) with optical and magnetic properties provide a means to understand intrinsic energy levels of 4f ions and their influence on optical and magnetic behaviour. Fundamental understanding of their luminescent and slow relaxation of the magnetization behaviour is critical for targeting and designing SMMs with multiple functionalities. Herein, we seek to investigate the role of Dy III coordination environment and fine electronic structure on the slow magnetic relaxation and luminescence thermometry. Our findings are illustrated through two distinct Dy III complexes, [Dy 2 (bpm)(hexd) 6 ] (1) and [Dy 2 (bpm)(hpd) 6 ] (2), (bpm = 2,20-bipyrimidine, hexd = 2,4-hexanedione, hpd = 3,5-heptanedione), by comparing their features with a family of Dy III dinuclear species bridged by bpm. These findings highlight that the hexd - and hpd - ligands exhibit a similar effective barrier to the reversal of magnetization (280-290 K). The values are among the highest for dinuclear Dy III complexes bridged by bpm, due to the low distortion of the Dy III coordination polyhedra and the long Dy-N equatorial bonds. Furthermore, the luminescence performance is affected by the triplet state energy of the terminal ligand, influencing ligand-to-Dy III energy transfer. The hpd - ligand's higher T 1 state energy leads to poor ligand-to-Dy III energy transfer, limiting the use of 2 for luminescence thermometry. Conversely, this issue is absent in 1, which offers a relative thermal sensitivity of 0.1 to 0.7% K -1 (10 to 60 K) with a temperature uncertainty below 1 K. These findings contribute to our understanding of lanthanide-based SMMs and facilitate the design of multifunctional materials with tailored magnetic and luminescent properties for molecular electronics and beyond.

Discrete molecular organometallic europium(II) complexes are promising functional materials due to their ability to behave as highly sensitive band-shift luminescence thermometers. Furthering our understanding of the design principles salient to the emission behavior of such systems is important for developing them in this emerging application. To this end, a series of pseudo- C 4 v -symmetric organometallic europium(II) complexes bearing systematically varying ligand sets were synthesized and characterized to probe the influence of subtle structural modification on their optical properties. Opto-structural correlation analyses via variable-temperature single-crystal X-ray diffraction and photoluminescence spectroscopy reveal a remarkable variability in properties among structurally similar complexes and a convoluted dependence of the emission characteristics on the stereoelectronic properties of the ligands. A few factors of particular influence are nevertheless identified, including the distance between the europium(II) ion and the basal plane of the square-pyramidal coordination polyhedron, the presence of pendant electron density that might further interact with the excited-state 5d orbitals, and, qualitatively, the metal-ligand flexibility of the construct. These results help to elucidate principles that govern the luminescence properties of organometallic europium(II) complexes with an eye to enabling the rational design of high-performance luminescence thermometers of this genre.

Over the years, polynuclear cyclic or torus complexes have attracted increasing interest due to their unique metal topologies and properties. However, the isolation of polynuclear cyclic organometallic complexes is extremely challenging due to their inherent reactivity, which stems from the labile and reactive metal-carbon bonds. In this study, the pyrazine ligand undergoes a radical-radical cross-coupling reaction leading to the formation of a decanuclear [(Cp*) 20 Dy 10 (L1) 10 ] ⋅ 12(C 7 H 8 ) (1; where L1 = anion of 2-prop-2-enyl-2H-pyrazine; Cp* = pentamethylcyclopentadienyl) complex, where all Dy III metal centres are bridged by the anionic L1 ligand. Amongst the family of polynuclear Ln organometallic complexes bearing Cp R 2 Ln x units (Cp R = substituted cyclopentadienyl), 1 features the highest nuclearity obtained to date. In-depth computational studies were conducted to elucidate the proposed reaction mechanism and formation of L1, while probing of the magnetic properties of 1, revealed slow magnetic relaxation upon application of a static dc field., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The rational engineering of molecules is a powerful chemistry tool of pivotal importance in the fields of molecular magnetism and luminescence. Hence, systems that can be modulated via molecular engineering and composition control are expected to present extra versatility regarding the tunability of their properties. This is the case with molecular cluster aggregates (MCAs), high nuclearity molecular compounds. Herein, we demonstrate how the union of both strategies, namely, composition control and molecular engineering, can be employed to enhance molecular upconversion in MCAs. This was achieved by doping a {Gd 8 Er 2 Yb 10 } MCA with Ce III ions. By replacement of the optically silent Gd III ions with Ce III , the upconversion mechanism is modified due to Ce III -mediated cross-relaxation. In addition to this effect, we could also engineer the degree of metal site distortion due to the larger size of Ce III ions, relaxing the selection rules and impacting the upconversion quantum yield and luminescent thermometry. Opto-structural correlations demonstrate that the presented molecular engineering strategy can be used to enhance the performance of molecular upconverters.

The unique electronic nature of the 1,2,4,5-tetrazine or s -tetrazine (tz) ring has sparked tremendous scientific interest over the last few years. Tetrazines have found numerous applications, and their ability to coordinate to metal ions has opened the possibility of exploring their chemistry in both molecular systems and extended networks. The rich redox chemistry of s -tetrazines allows them to exchange electrons and switch between their dihydro (H 2 tz), neutral (tz), and radical (tz˙ - ) forms. Previous reports in the literature have observed electrochemically that a second electron can potentially be stored in the tetrazinyl ring and form a dianionic species. However, due to its extremely reactive nature, this has not been isolated before. Herein, the combination of strictly anhydrous and inert conditions, strong reducing agents, non-acidic solvents and most importantly blocking the accessibility of the nitrogen atoms by coordinating them to lanthanide ions allowed for the stabilization of a dianionic tetrazine in a lanthanocene complex. Three dinuclear metallocene complexes are reported, [(Cp* 2 Ln) 2 (tz˙ - )(THF) 2 ](BPh 4 ) (Ln = Y (1-Y); Cp* = pentamethylcyclopentadienyl; THF = tetrahydrofuran) and [(Cp* 2 Ln) 2 (tz 2- )(THF) 2 ]·2THF (Ln = Gd (2-Gd), or Y (2-Y)), which utilize the unsubstituted tz as the ligand. In 1-Ln, the tz ligand is reduced to the radical anion (tz˙ - ), while in 2-Ln, the tz ligand is in the -2 charge state. These complexes are the first structurally and physically characterized complexes bearing the dianion radical of an s -tetrazine. Detailed structural analysis, ab initio calculations, and physical characterization support that the tz 2- ligand is a closed-shell planar dianion with unique structural features vastly different from those of the tz, tz˙ - and H 2 tz species., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Molecular systems known as single-molecule magnets (SMMs) exhibit magnet-like behaviour of slow relaxation of the magnetisation and magnetic hysteresis and have potential application in high-density memory storage or quantum computing. Often, their intrinsic magnetic properties are plagued by low-energy molecular vibrations that lead to phonon-induced relaxation processes, however, there is no straightforward synthetic approach for molecular systems that would lead to a small amount of low-energy vibrations and low phonon density of states at the spin-resonance energies. In this work, we apply knowledge accumulated over the last decade in molecular magnetism to nanoparticles, incorporating Er 3+ ions in an ultrasmall sub-3 nm diamagnetic NaYF 4 nanoparticle (NP) and probing the slow relaxation dynamics intrinsic to the Er 3+ ion. Furthermore, by increasing the doping concentration, we also investigate the role of intraparticle interactions within the NP. The knowledge gained from this study is anticipated to enable better design of magnetically high-performance molecular and bulk magnets for a wide variety of applications, such as molecular electronics., (© 2024. The Author(s).)

Single-ion anisotropy is vital for the observation of Single-Molecule Magnet (SMM) properties (i.e., a slow dynamics of the magnetization) in lanthanide-based systems. In the case of europium, the occurrence of this phenomenon has been inhibited by the spin and orbital quantum numbers that give way to J = 0 in the trivalent state and the half-filled population of the 4f orbitals in the divalent state. Herein, by optimizing the local crystal field of a quasi-linear bis(silylamido) Eu II complex, the [Eu II (N{SiMePh 2 } 2 ) 2 ] SMM is described, providing an example of a europium complex exhibiting slow relaxation of its magnetization. This behavior is dominated by a thermally activated (Orbach-like) mechanism, with an effective energy barrier of approximately 8 K, determined by bulk magnetometry and electron paramagnetic resonance. Ab initio calculations confirm second-order spin-orbit coupling effects lead to non-negligible axial magnetic anisotropy, splitting the ground state multiplet into four Kramers doublets, thereby allowing for the observation of an Orbach-like relaxation at low temperatures., (© 2024. The Author(s).)

Atomically defined large metal clusters have applications in new reaction development and preparation of materials with tailored properties. Expanding the synthetic toolbox for reactive high nuclearity metal complexes, we report a new class of Fe clusters, Tp* 4 W 4 Fe 13 S 12 , displaying a Fe 13 core with M-M bonds that has precedent only in main group and late metal chemistry. M 13 clusters with closed shell electron configurations can show significant stability and have been classified as superatoms. In contrast, Tp* 4 W 4 Fe 13 S 12 displays a large spin ground state of S=13. This compound performs small molecule activations involving the transfer of up to 12 electrons resulting in significant cluster rearrangements., (© 2023 Wiley-VCH GmbH.)

Reaction of the 1,2,4,5-tetrazine (tz˙ - ) radical and {Cp* 2 Tb} + has yielded a tetranuclear radical-bridged Tb III single-molecule magnet. The strong Ln-radical coupling and the electronic differences of the Tb III ions in [(Cp* 2 Tb) 4 (tz˙ - ) 4 ]·3C 6 H 6 (1) are probed via magnetic, magneto-optical and computational studies.

A proof-of-concept for magneto-optical barcodes is demonstrated for the first time. The dual-signalled spectrum observed via magnetic circular dichroism spectroscopy can be used to develop anti-counterfeiting materials with extra layers of security when compared with the widely studied luminescent barcodes.

The impact of composition control and energy transfer on luminescence thermometry was investigated in a Tb III /Eu III dual-emitting molecular cluster-aggregate, known as {Ln 20 }. The study of lifetime dynamics sheds new light on how one can take advantage of rational planning to enhance thermometric performance and gaining insights into intriguing optical properties.

Remote temperature probing at the cryogenic range is of utmost importance for the advancement of future quantum technologies. Despite the notable achievements in luminescent thermometers, accurately measuring temperatures below 10 K remains a challenging endeavor. In this study, we propose a novel magneto-optical thermometric approach based on the magnetic-circular dichroism (MCD) technique, which offers unprecedented capabilities for meticulous temperature variation analysis at cryogenic temperatures. The inherent temperature sensitivity of the MCD C-term, in conjunction with both positive and negative signals, enables highly sensitive magneto-optical temperature probing. Additionally, a groundbreaking relative thermal sensitivity value of 95.3 % K -1 at 2.54 K can be achieved using a mononuclear lanthanide complex, [[Ho(acac) 3 (phen)], in the presence of a 0.25 T applied magnetic field and using a combination of multiparametric thermal read-out with multiple regression. These results unequivocally demonstrate the viability and effectiveness of our methodology for cryogenic temperature sensing., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Composition control is a powerful tool for obtaining high-performance lanthanide (Ln) luminescent materials with adjustable optical outputs. This strategy is well-established for hierarchically structured nanoparticles, but it is rarely applied to molecular compounds due to the limited number of metal centers within a single unit. In this work, we present a series of molecular cluster-aggregates (MCAs) with an icosanuclear core {Ln 2 Eu 2 Tb 16 } (Ln = Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Tm, and Yb) in which we explore composition control, akin to nanoparticles, to modulate the optical output. More specifically, we target to understand how the presence of a third Ln III doping ion would impact the well-known Tb III → Eu III energy transfer and the ratiometric optical thermometry performance based on the Tb III /Eu III pair. Photophysical properties at room and at varying temperatures were investigated. Based on experimental data and well-established intrinsic features, such as spin-orbit coupling strength and Ln III 4 f energy levels' structure, we discuss the possible luminescent processes present in each MCA and provide insight into qualitative trends that can be rationally correlated throughout the series.