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1. Strong enhancement of magnetic ordering temperature and structural/valence transitions in EuPd ₃ S ₄ under high pressure

   https://doi.org/10.1073/pnas.2310779120  

   Huyan, Shuyuan; Ryan, Dominic H.; Slade, Tyler J.; Lavina, Barbara; Jose, Greeshma; Wang, Haozhe; Wilde, John M.; Ribeiro, Raquel A.; Zhao, Jiyong; Xie, Weiwei; et al (December 2023, Proceedings of the National Academy of Sciences)

   We present a comprehensive study of the inhomogeneous mixed-valence compound, EuPd₃S₄, by electrical transport, X-ray diffraction, time-domain¹⁵¹Eu synchrotron Mössbauer spectroscopy, and X-ray absorption spectroscopy measurements under high pressure. Electrical transport measurements show that the antiferromagnetic ordering temperature,T_N, increases rapidly from 2.8 K at ambient pressure to 23.5 K at ~19 GPa and plateaus between ~19 and ~29 GPa after which no anomaly associated withT_Nis detected. A pressure-induced first-order structural transition from cubic to tetragonal is observed, with a rather broad coexistence region (~20 GPa to ~30 GPa) that corresponds to theT_Nplateau. Mössbauer spectroscopy measurements show a clear valence transition from approximately 50:50 Eu²⁺:Eu³⁺to fully Eu³⁺at ~28 GPa, consistent with the vanishing of the magnetic order at the same pressure. X-ray absorption data show a transition to a fully trivalent state at a similar pressure. Our results show that pressure first greatly enhancesT_N, most likely via enhanced hybridization between the Eu 4fstates and the conduction band, and then, second, causes a structural phase transition that coincides with the conversion of the europium to a fully trivalent state. 

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2. [Ga ³⁺ ₈ Sm ³⁺ ₂ , Ga ³⁺ ₈ Tb ³⁺ ₂ ] Metallacrowns are Highly Promising Ratiometric Luminescent Molecular Nanothermometers Operating at Physiologically Relevant Temperatures

   https://doi.org/10.1002/chem.202003239  

   Salerno, Elvin_V; Zeler, Justyna; Eliseeva, Svetlana_V; Hernández‐Rodríguez, Miguel_A; Carneiro_Neto, Albano_N; Petoud, Stéphane; Pecoraro, Vincent_L; Carlos, Luís_D (September 2020, Chemistry – A European Journal)

   Abstract Nanothermometry is the study of temperature at the submicron scale with a broad range of potential applications, such as cellular studies or electronics. Molecular luminescent‐based nanothermometers offer a non‐contact means to record these temperatures with high spatial resolution and thermal sensitivity. A luminescent‐based molecular thermometer comprised of visible‐emitting Ga³⁺/Tb³⁺and Ga³⁺/Sm³⁺metallacrowns (MCs) achieved remarkable relative thermal sensitivity associated with very low temperature uncertainty ofS_r=1.9 % K⁻¹andδT<0.045 K, respectively, at 328 K, as an aqueous suspension of polystyrene nanobeads loaded with the corresponding MCs. To date, they are the ratiometric molecular nanothermometers offering the highest level of sensitivity in the physiologically relevant temperature range. 

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3. Detection of phosphates in water utilizing a Eu ³⁺ -mediated relay mechanism

   https://doi.org/10.1039/D1NJ04578D  

   Farshbaf, Sepideh; Dey, Kaustav; Mochida, Wakana; Kanakubo, Masashi; Nishiyabu, Ryuhei; Kubo, Yuji; Anzenbacher, Pavel (January 2022, New Journal of Chemistry)

   Three carboxamidequinoline ligands were synthesized and their complexes with Eu 3+ were used for recognition and detection of organic/inorganic phosphates in water. The signal transduction process is based on an “On–Off–On” switch in the fluorescence signal utilizing changes in the intramolecular charge transfer (ICT). The fluorescence emission of ligands is quenched upon exposure to the Eu 3+ (Off signal). Following the addition of the phosphate analytes the ligand–Eu 3+ complex disassembles, which results in the regeneration of the original emission of the ligand (On signal). In general, the Eu 3+ complexes show higher affinity towards adenosine 5′-triphosphate (ATP) and lower affinity to other phosphates, namely adenosine 5′-diphosphate (ADP), adenosine 5′-monophosphate (AMP), pyrophosphate (H 2 P 2 O 7 2− , PPi), and dihydrogenphosphate (H 2 PO 4 − , Pi). 

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4. High‐Resolution Photoelectron Imaging of IrB ₃ ⁻ : Observation of a π‐Aromatic B ₃ ⁺ Ring Coordinated to a Transition Metal

   https://doi.org/10.1002/anie.201902406  

   Czekner, Joseph; Cheung, Ling Fung; Kocheril, G. Stephen; Kulichenko, Maksim; Boldyrev, Alexander I.; Wang, Lai‐Sheng (May 2019, Angewandte Chemie International Edition)

   Abstract In a high‐resolution photoelectron imaging and theoretical study of the IrB₃⁻cluster, two isomers were observed experimentally with electron affinities (EAs) of 1.3147(8) and 1.937(4) eV. Quantum calculations revealed two nearly degenerate isomers competing for the global minimum, both with a B₃ring coordinated with the Ir atom. The isomer with the higher EA consists of a B₃ring with a bridge‐bonded Ir atom (C_s,²A′), and the second isomer features a tetrahedral structure (C_3v,²A₁). The neutral tetrahedral structure was predicted to be considerably more stable than all other isomers. Chemical bonding analysis showed that the neutralC_3visomer involves significant covalent Ir−B bonding and weak ionic bonding with charge transfer from B₃to Ir, and can be viewed as an Ir–(η³‐B₃⁺) complex. This study provides the first example of a boron‐to‐metal charge‐transfer complex and evidence of a π‐aromatic B₃⁺ring coordinated to a transition metal. 

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5. Lanthanide Identity Governs Guest‐Induced Dimerization in Ln ^III [15‐MC _N(L‐pheHA) ‐5]) ³⁺ Metallacrowns

   https://doi.org/10.1002/chem.202103263  

   Sgarlata, Carmelo; Schneider, Bernadette_L; Zito, Valeria; Migliore, Rossella; Tegoni, Matteo; Pecoraro, Vincent_L; Arena, Giuseppe (November 2021, Chemistry – A European Journal)

   Abstract Series of lanthanide‐containing metallic coordination complexes are frequently presented as structurally analogous, due to the similar chemical and coordinative properties of the lanthanides. In the case of chiral (Ln^III[15‐MC_N(L‐pheHA)‐5])³⁺metallacrowns (MCs), which are well established supramolecular hosts, the formation of dimers templated by a dicarboxylate guest (muconate) in solution of neutral pH is herein shown to have a unique dependence on the identity of the MC's central lanthanide. Calorimetric data and nuclear magnetic resonance diffusion studies demonstrate that MCs containing larger or smaller lanthanides as the central metal only form monomeric host‐guest complexes whereas analogues with intermediate lanthanides (for example, Eu, Gd, Dy) participate in formation of dimeric host‐guest‐host compartments. The driving force for the dimerization event across the series is thought to be a competition between formation of highly stable MCs (larger lanthanides) and optimally linked bridging guests (smaller lanthanides). 

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