Ming-Liang Tong

Hydroxylation of N‐Heterocycle Ligands Observed in Two Unusual Mixed‐Valence CuI/CuII Complexes

The chelate ligands 2,2 -bipyridine (bpy), 1,10-phenanthroline (phen), and their substituted derivatives have played an important role in the development of coordination chemistry,[1, 2] and over the decades a number of so-called anomalies have been reported in reactions of their metal complexes. To rationalize the anomalous properties of complexes such as [M(bpy)3] and [M(phen)3] , Gillard borrowed the idea of TMcovalent hydrates∫ from the organic literature and proposed an interesting mechanism,[3] the core of which is nucleophilic attack of a hydroxide ion on a coordinated heterocyclic ligand to form a covalent hydrate (CH); this may react further by intramolecular shift of OH or H2O onto the metal before the formation of the final products (Scheme 1). The mechanism

Symmetry-Supported Magnetic Blocking at 20 K in Pentagonal Bipyramidal Dy(III) Single-Ion Magnets

Single-molecule magnets (SMMs) that can be trapped in one of the bistable magnetic states separated by an energy barrier are among the most promising candidates for high-density information storage, quantum processing, and spintronics. To date, a considerable series of achievements have been made. However, the presence of fast quantum tunnelling of magnetization (QTM) in most SMMs, especially in single-ion magnets (SIMs), provides a rapid relaxation route and often sets up a limit for the relaxation time. Here, we pursue the pentagonal bipyramidal symmetry to suppress the QTM and present pentagonal bipyramidal Dy(III) SIMs [Dy(Cy3PO)2(H2O)5]Cl3·(Cy3PO)·H2O·EtOH (1) and [Dy(Cy3PO)2(H2O)5]Br3·2(Cy3PO)·2H2O·2EtOH (2), (Cy3PO = tricyclohexyl phosphine oxide). Magnetic characterizations reveal their fascinating SMM properties with high energy barriers as 472(7) K for 1 and 543(2) K for 2, along with a record magnetic hysteresis temperature up to 20 K for 2. These results, combined with the ab initio calculations, offer an illuminating insight into the vast possibility and potential of what the symmetry rules can achieve in molecular magnetism.

Switching the anisotropy barrier of a single-ion magnet by symmetry change from quasi-D5h to quasi-Oh

A reversible single-crystal-to-single-crystal transformation is used to dramatically change the relaxation behavior of a single-ion magnet. The coordination geometry of the DyIII site of a [Zn–Dy–Zn] complex changes from pentagonal–bipyramid (quasi-D5h) to octahedron (quasi-Oh), inducing an energy barrier change from 305 cm−1 (439 K) to a negligible value, respectively. Ab initio calculations reveal that the ideal D5h–DyIII is of perfect axiality with a substantial energy barrier in accordance with the experimental result.

Silver(I)–hexamethylenetetramine molecular architectures: from self-assembly to designed assembly

Abstract The investigations on the construction of silver(I)–hexamethylenetetramine coordination networks containing different additional ligands and counter anions have been reviewed. The interesting topologies, synthetic approaches and the important factors that influence the structures, as well as some designed assembly approaches are described.

A Dysprosium Metallocene Single‐Molecule Magnet Functioning at the Axial Limit

Abstraction of a chloride ligand from the dysprosium metallocene [(Cpttt )2 DyCl] (1Dy Cpttt =1,2,4-tri(tert-butyl)cyclopentadienide) by the triethylsilylium cation produces the first base-free rare-earth metallocenium cation [(Cpttt )2 Dy]+ (2Dy ) as a salt of the non-coordinating [B(C6 F5 )4 ]- anion. Magnetic measurements reveal that [2Dy ][B(C6 F5 )4 ] is an SMM with a record anisotropy barrier up to 1277 cm-1 (1837 K) in zero field and a record magnetic blocking temperature of 60 K, including hysteresis with coercivity. The exceptional magnetic axiality of 2Dy is further highlighted by computational studies, which reveal this system to be the first lanthanide SMM in which all low-lying Kramers doublets correspond to a well-defined MJ value, with no significant mixing even in the higher doublets.

Polynuclear and polymeric gadolinium acetate derivatives with large magnetocaloric effect.

Two ferromagnetic μ-oxo(acetate)-bridged gadolinium complexes [Gd(2)(OAc)(2)(Ph(2)acac)(4)(MeOH)(2)] (1) and [Gd(4)(OAc)(4)(acac)(8)(H(2)O)(4)] (2) and two polymeric Gd(III) chains [Gd(OAc)(3)(MeOH)](n) (3) and [Gd(OAc)(3)(H(2)O)(0.5)](n) (4) (Ph(2)acacH = dibenzoylmethane; acacH = acetylacetone) are reported. The magnetic studies reveal that the tiny difference in the Gd-O-Gd angles (Gd···Gd distances) in these complexes cause different magnetic coupling. There exist ferromagnetic interactions in 1-3 due to the presence of the larger Gd-O-Gd angles (Gd···Gd distances), and antiferromagnetic interaction in 4 when the Gd-O-Gd angle is smaller. Four gadolinium acetate derivatives display large magnetocaloric effect (MCE). The higher magnetic density or the lower M(W)/N(Gd) ratio they have, the larger MCE they display. Complex 4 has the highest magnetic density and exhibits the largest MCE (47.7 J K(-1) kg(-1)). In addition, complex 3 has wider temperature and/or field scope of application in refrigeration due to the dominant ferromagnetic coupling. Moreover, the statistical thermodynamics on entropy was successfully applied to simulate the MCE values. The results are quite in agreement with those obtained from experimental data.

A six-coordinate ytterbium complex exhibiting easy-plane anisotropy and field-induced single-ion magnet behavior.

The field-induced blockage of magnetization behavior was first observed in an Yb(III)-based molecule with a trigonally distorted octahedral coordination environment. Ab initio calculations and micro-SQUID measurements were performed to demonstrate the exhibition of easy-plane anisotropy, suggesting the investigated complex is the first pure lanthanide field-induced single-ion magnet (field-induced SIM) of this type. Furthermore, we found the relaxation time obeys a power law instead of an exponential law, indicating that the relaxation process should be involved a direct process rather than an Orbach process.

A Heterometallic FeII–DyIII Single‐Molecule Magnet with a Record Anisotropy Barrier

A record anisotropy barrier (319 cm(-1) ) for all d-f complexes was observed for a unique Fe(II) -Dy(III) -Fe(II) single-molecule magnet (SMM), which possesses two asymmetric and distorted Fe(II) ions and one quasi-D5h Dy(III) ion. The frozen magnetization of the Dy(III) ion leads to the decreased Fe(II) relaxation rates evident in the Mössbauer spectrum. Ab initio calculations suggest that tunneling is interrupted effectively thanks to the exchange doublets.

The First {Dy4} Single-Molecule Magnet with a Toroidal Magnetic Moment in the Ground State

A toroidal magnetic moment in the absence of a conventional total magnetic moment was first observed in a novel tetranuclear dysprosium cluster with nonmagnetic ground state. The toroidal state is quite robust with respect to variations of the exchange parameters.

A novel three-dimensional coordination polymer constructed with mixed-valence dimeric copper(i,ii) unitsElectronic supplementary information (ESI) available: synthesis and data for 1. See http://www.rsc.org/suppdata/cc/b2/b210914j/

A novel three-dimensional coordination polymer with a mixed-valence localized copper(I,II) dimeric unit, [Cu2(4-pya)3]n (4-pya = 4-pyridinecarboxylate), was hydrothermally synthesized via a simultaneous in-situa redox and hydrolysis reaction of Cu(II) and 4-cyanopyridine and crystallographically characterized to be a twofold interpenetrated three-dimensional coordination network with a cubic [Cu16(4-pya)12] building unit.