Photochromic Dysprosium Single-Molecule Magnet Featuring Reversible Redox Transformation of Polyoxomolybdate Moiety.

A photochromic dysprosium-based single-molecule magnet [Dy(CyPhPO)(HO)](PMoO) ⋅ 3CyPhPO⋅HO (1-Dy) is synthesized via cocrystal engineering of a polyoxomolybdate (POMo) anion and an Ising-type cation with pseudo pentagonal bipyramidal geometry. Upon ultraviolet irradiation, Mo-to-Mo single-electron photoreduction occurs in the POMo moiety, resulting in significant changes of optical and magnetic properties. The emergence of intervalence charge-transfer transitions in heteropoly blue state 1-Dy* facilitates photothermal conversion in near-infrared region.

Two 2D spin-crossover coordination polymers constructed by [Pd(SCN)] building blocks.

Two new two-dimensional (2D) coordination polymers, [Fe(L){Pd(SCN)}] (L = 2-methoxypyrazine, 1; and L = ()-3-(phenyldiazenyl)pyridine, 2), were successfully constructed by using square-planar [Pd(SCN)] building blocks. Complex 1 exhibits complete and one-step spin-crossover (SCO) behavior, while 2 exhibits incomplete and two-step SCO behavior. Further structural insight into this synergy reveals that the flat/flexing [Fe{Pd(SCN)}] sheets in 1 and 2 are stabilized by interlayered/intralayered supramolecular interactions.

Integrating Polyoxometalate into Dy(III)-based Single-molecule Magnets with Pentagonal Bipyramidal Symmetry.

Polyoxometalates (POMs) with various coordination fashions are versatile ligands for constructing single-ion magnets (SIMs), but enforcing POM-SIMs with a specific geometry remains a synthetic challenge. Herein, we synthesized a POM-cocrystallized Dy-SIM [Dy(OPPh)(HO)][PWO]·4EtOH () and a POM-ligated Dy-SIM [{Dy(OPPh)(HO)}{PWO}]·PhPO·HO () with pentagonal bipyramidal local coordination geometry. Magnetic measurements indicate that displays field-induced single-molecule magnet (SMM) behavior and the relaxation is dominated by under-barrier processes.

Phase Transition Control in Molecular Solids via Complementarity of Hydrogen-Bond Strength.

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 Co compounds were isolated and systematically investigated by modifying the ligand terminal groups (X=S, Se) and substituents (Y=Cl, Br).

Spin-State Control in Dysprosium(III) Metallacrown Magnets via Thioacetal Modification.

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 [DyNi(quinha)(sal)(py)](ClO) ⋅ 4HO (Hquinha=quinaldichydroxamic acid, Hsal=5-chlorosalicylaldehyde) wherein a square planar Ni is stabilized by chemical stacking. Thioacetal modification was employed via post-synthetic ligand substitutions and yielded [DyNi(quinha)(saldt)(py)](ClO) ⋅ 3HO (Hsaldt=4-chloro-2-(1,3-dithiolan-2-yl)phenol).

Two-dimensional spin-crossover coordination polymers based on the 1,1,2,2-tetra(pyridin-4-yl)ethene ligand.

A series of two-dimensional (2D) spin-crossover coordination polymers (SCO-CPs) [Fe(TPE)(NCX)]·solv (1: X = BH, solv = HO·2CHOH·DMF; 2: X = Se, solv = HO·2CHOH·0.5DMF; 3: X = S, solv = HO·2CHOH·0.5DMF) were synthesized by employing 1,1,2,2-tetra(pyridin-4-yl)ethene (TPE) and pseudohalide (NCX) coligands.

Cyanometallic charge engineering in spin crossover metal-organic frameworks.

In this study, we successfully synthesize cationic/neutral/anionic inverse-Hofmann-type spin crossover (SCO) frameworks with 1,1,2,2-tetrakis(4-(pyridine-4-yl)phenyl)-ethene ligand by means of cyanometallic charge engineering strategy. The cationic and neutral frameworks exhibit single-step thermally induced spin transition behaviors, while the SCO capability of anionic framework can be aroused by partial desolvation. This strategy provides a new idea to construct ionic SCO frameworks and extends the toolkit for SCO materials.

Single-Crystal Transformation Engineering the Spin Change of Metal-Organic Frameworks via Cluster Deconstruction.

Spin crossover (SCO) materials with new architectures will expand and enrich the research in the SCO field. Here, we report two metal-organic frameworks (MOFs) containing tetradentate organic ligands and hexatopic linkers [Ag X (CN) ] (X=Br and I), which represents the first SCO MOF with clusters as building blocks. The silver halide cluster can be further removed after reacting with lithium tetracyanoquinodimethan (LiTCNQ).

High-stability spherical lanthanide nanoclusters for magnetic resonance imaging.

High-nuclear lanthanide clusters have shown great potential for the administration of high-dose mononuclear gadolinium chelates in magnetic resonance imaging (MRI). The development of high-nuclear lanthanide clusters with excellent solubility and high stability in water or solution has been challenging and is very important for expanding the performance of MRI. We used -methylbenzimidazole-2-methanol (HL) and LnCl·6HO to synthesize two spherical lanthanide clusters, Ln (Ln = Ho, Ho; and Ln = Gd, Gd), which are highly stable in solution.

Lanthanide-radical single-molecule magnets: current status and future challenges.

In the field of molecular magnetism, the lanthanide-radical (Ln-Rad) method has become one of the most appealing tactics for introducing strong magnetic interactions and has spurred on the booming development of heterospin single-molecule magnets (SMMs). The article is a timely retrospect on the research progress of Ln-Rad heterospin systems and special attention is invested on low dimensional Ln-Rad compounds with SMM behavior, primarily concerning with nitrogen-based radicals, semiquinone and nitroxide radicals. Rational design, molecular structures, magnetic behaviors and magneto-structural correlations are highlighted.

Magnetic and Luminescent Dual Responses of Photochromic Hexaazamacrocyclic Lanthanide Complexes.

Herein, hexaazamacrocyclic ligand L was employed to construct a series of photochromic rare-earth complexes, [Ln(L)(NO)](BPh) [, Ln = Dy, Tb, Eu, Gd, Y; L = (3,5,10,12)-3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane-3,5,10,12-tetraene]. The behavior of photogenerated radicals of hexaazamacrocyclic ligands was revealed for the first time. Upon 365 nm light irradiation, complexes exhibit photochromic behavior induced by photogenerated radicals according to EPR and UV-vis analyses.

Redox-Programmable Spin-Crossover Behaviors in a Cationic Framework.

Metal-organic frameworks (MOFs) provide versatile platforms to construct multi-responsive materials. Herein, by introducing the neutral tetradentate ligand and the linear dicyanoaurate(I) anion, we reported a rare cationic MOF [Fe(TPB){Au(CN)}]I·4HO·4DMF (TPB = 1,2,4,5-tetra(pyridin-4-yl)benzene) with hysteretic spin-crossover (SCO) behavior near room temperature. This hybrid framework with an open metal site (Au) exhibits redox-programmable capability toward dihalogen molecules.

Single-Crystal to Single-Crystal Transformation of a Spin-Crossover Hybrid Perovskite via Thermal-Induced Cyanide Linkage Isomerization.

Linkage isomers involving changes in the bonding mode of ambidentate ligands have potential applications in data storage, molecular machines, and motors. However, the observation of the cyanide-linkage-isomerism-induced spin change (CLIISC) effect characterized by single-crystal X-ray diffraction remains a considerable challenge. Meanwhile, the high-spin and low-spin states can be reversibly switched in spin-crossover (SCO) compounds, which provide the potential for applications to data storage, switches, and sensors.

Fascinating interlocked triacontanuclear giant nanocages.

We report herein three air, thermal and solvent stable interlocked triacontanuclear giant nanocages, generated using a node and spacer concept. Interestingly, the crystal structures of the cages are not only nano-dimensional but also exist in the nano-dimension range, which was corroborated with microscopic images. The combination of microscopic and crystallographic data, in effect, led us to a unique advantageous situation of generating nanomaterials with hard-to-come-by structural information at the molecular level.

Tuning luminescence of didysprosium single-molecule magnets with a π-conjugated/non-conjugated bridging ligand.

Herein, we reported two didysprosium single-molecule magnets constructed with {Dy(bbpen)(MeOH)} subunits and a π-conjugated tpb or non-conjugated tpcb bridging ligand. The former exhibits extremely weak luminescence that makes it difficult to simulate its emission spectra. However, the later shows obviously enhanced and well-resolved luminescence, which helps us to gain knowledge about the magneto-optical correlation and the relevant magnetic energy levels.

A spin-crossover phenomenon in a 2D heterometallic coordination polymer with [Pd(SCN)] building blocks.

Two new two-dimensional (2D) coordination polymers, [Fe(L){Pd(SCN)}] (L = 3-(9-anthracenyl)-pyridine (1) and L = 4-(9-anthracenyl)-pyridine (2)), were constructed by employing square-planar [Pd(SCN)] building blocks. Compound 1 exhibits a complete spin-crossover (SCO) behaviour under normal atmospheric pressure, and represents the first SCO example in a 2D system containing [Pd(SCN)] units. In contrast, compound 2 only shows paramagnetic behaviour at measured temperatures.

Opening Magnetic Hysteresis by Axial Ferromagnetic Coupling: From Mono-Decker to Double-Decker Metallacrown.

Combining Ising-type magnetic anisotropy with collinear magnetic interactions in single-molecule magnets (SMMs) is a significant synthetic challenge. Herein we report a Dy[15-MC -5] (1-Dy) SMM, where a Dy ion is held in a central pseudo-D pocket of a rigid and planar Cu metallacrown (MC). Linking two Dy[15-MC -5] units with a single hydroxide bridge yields the double-decker {Dy[15-MC -5]} (2-Dy) SMM where the anisotropy axes of the two Dy ions are nearly collinear, resulting in magnetic relaxation times for 2-Dy that are approximately 200 000 times slower at 2 K than for 1-Dy in zero external field.

Magnetic dynamics of an open-ring tridysprosium complex employing mixed ligands.

By employing mixed ligands, a new trinuclear dysprosium complex [Dy3(dbm)3(L)4](ClO4)2·CH2Cl2·2MeOH (1, Hdbm = dibenzoylmethane; HL = 2-methoxy-6-((quinolin-8-ylimino)methyl)phenol) was synthesized by a one-pot reaction. According to structural characterization, all the 8-coordinated Dy(iii) sites are well arranged with slightly distorted square antiprism (D4d) geometries. Magnetic measurements reveal that 1 exhibits typical single-molecule magnetic behavior at zero magnetic field and shows rarely open hysteresis loops up to 3 K among open-ring {Dy3} SMMs, where the relaxation time remains very stable under the protection from the Dy-Dy magnetic coupling in the open-ring arrangement of Ising spins.

Spin-crossover in an organic-inorganic hybrid perovskite.

The first spin-crossover (SCO) complex with an organic-inorganic hybrid perovskite structure (PPN)[Fe{Au(CN)}] (1) is reported, which displays three-step SCO behaviour. The light-induced excited spin-state trapping measurement gives T = 134 K for a three-dimensional FeL-type (L = bis-monodentate ligand) SCO complex. Moreover, spin-state dependent fluorescence is observed in 1.

Slow magnetic dynamics in centrosymmetric didysprosium and equilateral triangular tridysprosium molecules.

Single-molecule magnets (SMMs) with higher nuclearity provide opportunity for understanding the inherent nature of magnetic dynamics that are not limited to mononuclear SMMs. Herein, centrosymmetric [Dy2(L)2(9-AC)4(MeOH)2]·2CH2Cl2·2H2O (1, where 9-AC = anthracene-9-carboxylate) and equilateral triangular [Dy3(OH)(OMe)(L)3(dbm)3](OH)·3CH2Cl2·7H2O (2, where dbm = dibenzoylmethane anion) were isolated using the Schiff-base ligand 4-(anthracen-9-yl)-2-((quinolin-8-ylimino)methyl)phenol (HL). Static and dynamic magnetic measurements reveal that 1 and 2 display slow magnetic relaxation under zero and applied dc field, respectively.

Cyanometallate-Bridged Didysprosium Single-Molecule Magnets Constructed with Single-Ion Magnet Building Block.

The combination of magnetic interaction with high magnetic anisotropy provides a promising way for modulating/fine-tuning molecular magnetic behaviors. Here, we show the building block approach for the synthesis of a family of dilanthanide single-molecule magnets (SMMs) bridged with a cyanometallate starting from a monolanthanide SMM. Contingent on the central para-/diamagnetic [M(CN)] (M = Fe, Co) integrated between two highly anisotropic pentagonal-bipyramid Dy(III) subunits, the remanence of magnetization is OFF/ON below 15 K and they respectively display a record reversal barrier of 659 K among d-f SMMs and 975 K among cyano-bridged SMMs.

Chiral Erbium(III) Complexes: Single-Molecule Magnet Behavior, Chirality, and Nuclearity Control.

The reactions of chiral ligand ()/()-1,1'-binaphthyl-2,2'-diyl phosphate (-HL/-HL) and ErCl·6HO afford two pairs of di- and tetranuclear enantiomers [Er(/-L)(EtOH)]Cl·6.5EtOH (-, -) and [Er(PO)(/-L)(EtOH)(HO)]Cl(OH)·15EtOH·11HO (-, -). The nuclearity of these complexes is controllable and depends on the reaction temperature with a template effect.

A square antiprism dysprosium single-ion magnet with an energy barrier over 900 K.

Herein we report a stable and high-performance Dy(iii) single-ion magnet (SIM) showing an energy barrier of 944 K under zero dc field, with an open hysteresis loop up to 6 K. To the best of our knowledge, this is the highest energy barrier for a square antiprism as well as phosphine oxide based Dy-SIMs, reported so far.