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Integrating controllable spin states into single‐molecule magnets (SMMs) enables precise manipulation of magnetic interactions at a molecular level, but remains a synthetic challenge. Herein, we developed a 3d–4f metallacrown (MC) magnet [DyNi5(quinha)5(Clsal)2(py)8](ClO4) ⋅ 4H2O (H2quinha=quinaldichydroxamic acid, HClsal=5‐chlorosalicylaldehyde) wherein a square planar NiII is stabilized by chemical stacking. Thioacetal modification was employed via post‐synthetic ligand substitutions and yielded [DyNi5(quinha)5(Clsaldt)2(py)8](ClO4) ⋅ 3H2O (HClsaldt=4‐chloro‐2‐(1,3‐dithiolan‐2‐yl)phenol). Thanks to the additional ligations of thioacetal onto the NiII site, coordination‐induced spin state switching (CISSS) took place with spin state altering from low‐spin S=0 to high‐spin S=1. The synergy of CISSS effect and magnetic interactions results in distinct energy splitting and magnetic dynamics. Magnetic studies indicate prominent enhancement of reversal barrier from 57 cm−1 to 423 cm−1, along with hysteresis opening and an over 200‐fold increment in coercive field at 2 K. Ab initio calculations provide deeper insights into the exchange models and rationalize the relaxation/tunnelling pathways. These results demonstrate here provide a fire‐new perspective in modulating the magnetization relaxation via the incorporation of controllable spin states and magnetic interactions facilitated by the CISSS approach. [ABSTRACT FROM AUTHOR]

Phase transitions in molecular solids involve synergistic changes in chemical and electronic structures, leading to diversification in physical and chemical properties. Despite the pivotal role of hydrogen bonds (H‐bonds) in many phase‐transition materials, it is rare and challenging to chemically regulate the dynamics and to elucidate the structure‐property relationship. Here, four high‐spin CoII compounds were isolated and systematically investigated by modifying the ligand terminal groups (X=S, Se) and substituents (Y=Cl, Br). S−Cl and Se−Br undergo a reversible structural phase transition near room temperature, triggering the rotation of 15‐crown‐5 guests and the swing between syn‐ and anti‐conformation of NCX− ligands, accompanied by switchable magnetism. Conversely, S−Br and Se−Cl retain stability in ordered and disordered phases, respectively. H‐bonds geometric analysis and ab initio calculations reveal that the electronegativity of X and Y affects the strength of NY‐ap−H⋅⋅⋅X interactions. Entropy‐driven structural phase transitions occur when the H‐bond strength is appropriate; otherwise, the phase stays unchanged if it is too strong or weak. This work highlights a phase transition driven by H‐bond strength complementarity – pairing strong acceptor with weak donor and vice versa, which offers a straightforward and effective approach for designing phase‐transition molecular solids from a chemical perspective. [ABSTRACT FROM AUTHOR]

The relaxation time under zero field reflects the memory retention capabilities of single‐molecule magnets (SMMs) when used as storage devices. Intermolecular magnetic dipole interaction is ubiquitous in aggregates of magnetic molecules and can greatly influence relaxation times. However, such interaction is often considered harmful and challenging to manipulate in molecular solids, especially for high‐performance lanthanide single‐ion magnets (SIMs). By an elaborately designed combination of ion pairing and hydrogen bonding, we have synthesized two pseudo‐D5h SIMs with supramolecular arrangements of magnetic dipoles in staggered and side‐by‐side patterns, the latter of which exhibits a 104‐fold slower zero‐field relaxation time at 2 K. Intriguingly, the side‐by‐side complex exhibits a significantly accelerated magnetic relaxation upon diamagnetic dilution, contrary to the general trend observed in the staggered complex. This strongly reveals the presence of aggregation‐induced suppression of quantum tunneling in a side‐by‐side arrangement, which has not been observed in mononuclear SMMs. By leveraging ion‐pairing aggregation and converting to a side‐by‐side pattern, this study successfully demonstrates an approach to transform a harmful intermolecular dipole interaction into a beneficial one, achieving a τQTM of 980 s ranking among the best‐performance SMMs. [ABSTRACT FROM AUTHOR]

By incorporating diprotonated terpyridine cations and hexacyanometalate(III) anions into supramolecular hybrid salts, formulated as (HTPY)(H2TPY)[MIII(CN)6]·5H2O where TPY = 2,2′:6′,2′′-terpyridine, M = Fe (1), Co(2), room temperature photoinduced electron transfer (PET) was achieved with the involvement of a [MIII(CN)6]3− ion. Characterization of the intrinsic nature unfolded unprecedented light-induced off→on magnetization and slow magnetic relaxation behaviour occurring for the M = Co analogue, which paves a promising way for photo-responsive multifunctional molecular materials. [ABSTRACT FROM AUTHOR]

Magnetically switchable molecular solids with stimuli-responsive ON/OFF characteristics are promising candidates for smart switches and magnetic storage. In addition to conventional spin-crossover/charge-transfer materials whose magnetic responses arise from changes in the electronic structure of the metal centers, peripheral chemical entities that exhibit tunability provide an alternative and promising tactic for the construction of magnetic multi-stable materials. Temperature changes can trigger a reversible structural phase transition that can affect the coordination environment of a transition-metal center because of the thermal-induced motion of ligands, counterions, neutral guests, and/or changes in coordination number, thus potentially realizing magnetic bistability which can arise from a concomitant spin state change or the modulation of orbital angular momentum. Perspectives and challenges are also highlighted to provide insights into its development. [ABSTRACT FROM AUTHOR]

The spectra emitted by highly charged ions, which are abundant in laboratory plasma and stellar systems, cover a wide range of wavelengths from near-infrared to x-rays. Measurements on such spectral lines can provide plasma information such as the electron temperature, electron/ion density, chemical composition, and the evolution of these parameters. To simulate the x-ray emission from comets and other celestial bodies irradiated by solar wind ions in the laboratory, we established an experimental platform for x-ray measurements at Institute of Modern Physics, Chinese Academy of Sciences, and measured the x-ray emission spectra from a series of metal and silicate minerals bombarded by slow highly charged nitrogen and oxygen ions. In this paper, we describe the x-ray measurement platform in detail and report the x-ray emission caused by the interaction of 1.5–20 keV/q Oq+ (q = 3, 5, 6) and Nq+ (q = 3, 5) ions with nickel surface. It is discovered that the measured x-ray yield and production cross section increase rapidly as increasing the impact energy, but have no discernible dependence on the charge state of incident ions. The experimental results reveal that the incident ions have been neutralized and achieved charge state equilibration before the K-shell electron is ionized. When the incident energy is greater than 5 keV/q, the Binary Encounter Approximation calculations are consistent well with the experimental data, indicating that the K-shell ionization of incident ions is due to direct Coulomb excitation processes that occur below the target surface. However, the experimental ionization cross sections clearly deviate from the Binary Encounter Approximation calculations when the impact energy is less than 5 keV/q. The discrepancy at the low collision energy is discussed and explained based on a multi-electron excitation model. [ABSTRACT FROM AUTHOR]

Introducing magnetic switchability into artificial molecular machines is fascinating for precise control of magnetism via external stimuli. Herein, a field‐induced CoII single‐molecule magnet was found to exhibit the reversible switch of Jahn–Teller distortion near room temperature, along with thermal conformational motion of the 18‐crown‐6 rotor, which pulls the coordinated H2O to rotate through intermolecular hydrogen bonds and triggers a single‐crystal‐to‐single‐crystal phase transition with Twarm=282 K and Tcool=276 K. Interestingly, the molecular magnetic anisotropy probed by single‐crystal angular‐resolved magnetometry revealed the reorientation of easy axis by 14.6°. Moreover, ON/OFF negative magnetodielectric effects were respectively observed in the high‐/low‐temperature phase, which manifests the spin‐lattice interaction in the high‐temperature phase could be stronger, in accompanied by the hydrogen bonding between the rotating 18‐crown‐6 and the coordinated H2O. [ABSTRACT FROM AUTHOR]

Through a mixed-ligand strategy, the structural change from a discrete dinuclear DyIII cluster to a one-dimensional polymeric chain was achieved, maintaining the two magnetic entities with the same {Dy(dppbO2)2(H2O)5} (dppbO2 = 1,4-butylenebis(diphenylphosphine oxide)) core structure. Since the hydrogen bonding between the equatorial coordinated water molecules and the guests/solvents/anions is distinct, the local geometry and the equatorial planarity of the first coordination sphere of the central DyIII ion become slightly different caused by the second coordination sphere. As a result, the dinuclear compound shows typical butterfly-shaped hysteresis loops, while it significantly opens at zero magnetic field up to 11 K for the 1D polymer, which is unprecedented in coordination polymers. Our experimental observations and theoretical analysis indicate that the hydrogen bonding leads to the fine-tuning of certain bond lengths and angles of the coordination environment, as well as the crystal field to a certain extent, revealing that the second coordination sphere affects the first coordination sphere by hydrogen bonding. [ABSTRACT FROM AUTHOR]

Due to the small differences in the chemical properties of facial (fac) and meridional (mer) stereoisomers, selective synthesis of one of the isomers is challenging, especially for lanthanide complexes. By using a flexible bidentate phosphine oxide ligand, we managed to isolate three stereoisomeric 2D and 3D coordination polymers, in which six-coordinate Dy(III) ions possess fac- or mer-Cl3O3 coordination environments. Structural studies indicate that the stereochemistry differences result from their various supramolecular interactions (e.g., hydrogen bonding and π⋯π stacking). Magnetic property measurements reveal the different static and dynamic magnetic behaviours of the three stereoisomers. Ab initio CASSCF calculations were then performed which indicated that their distinct magnetic behaviours arise from their fac/mer configurations. Compared to fac-Dy(III), mer-Dy(III) possesses more axial ground-state KDs and higher first excited KDs. [ABSTRACT FROM AUTHOR]

In this paper, K-shell X-ray spectra of nitrogen are measured by the interaction of Nq+ (q = 3, 5) ions with Al and Cu surfaces in the impact energy range of 25–100 keV. K-shell X-ray yields per incident ion and then ionization cross sections are deduced from the measured K-X-ray spectra. It is found that both the yields and cross sections increase quickly with increasing impact energy, but have no apparent dependence on the target material and the charge state of the incident ion. The experimental results reveal that the incident Nq+ (q = 3, 5) ions have been neutralized and achieved a charge-state equilibration before the K-shell electron is ionized. The experimental ionization cross sections are compared with those from the plane wave Born approximation (PWBA) and the classical binary encounter approximation (BEA) theory. The BEA calculations are better consistent with the experimental data than the PWBA. It means that the K-shell ionization of the incident Nq+ (q = 3, 5) ions is due to the direct Coulomb excitation processes that occurred below the target surface. K-shell ionization cross sections of Nq+ ions incident on an Al target. The theoretical calculations of BEA and PWBA models are also shown for comparison [ABSTRACT FROM AUTHOR]