Isolation of 1,4,5,8-tetraazanaphthalene radicals.

The first radicals of 1,4,5,8-tetraazanaphthalene have been synthesised and proven by crystallography, EPR spectroscopy and DFT calculations. As confirmed by four-probe conductivity measurements, the radicals are semiconducting.

Slow Magnetic Relaxation in a Rare, Neutral, Formally Divalent Terbium Bis(amide) Complex.

Neutral organometallic complexes containing a formally divalent terbium ion are especially scarce, owing to the highly negative Tb/Tb reduction potential and the thermodynamic stability of the Tb ion. In fact, there are only two crystallographically characterized neutral terbium(II) complexes known to date. Here, we present the synthesis of the unprecedented heteroleptic Tb(III) bis(amide) chloride complex, (NHAr*)TbCl () (where Ar* = 2,6-(Ar')CH, Ar' = 2,4,6-(Pr)CH), which was chemically reduced using the strong reducing agent, KC, to yield a new member of this small family of highly reactive Tb compounds, namely, the homoleptic terbium bis(amide) complex, (NHAr*)Tb ().

Magnetic Hysteresis in a Dysprosium Bis(amide) Complex.

Here, we present the synthesis and characterization of two mononuclear dysprosium molecules. The first complex is neutral and contains two triarylamide ligands coordinating to a Dy ion that is additionally ligated to a chloride anion, in the form of (NHAr*)DyCl (). Treatment of with Tl[BArF] prompted the removal of the chloride as TlCl from the first coordination sphere to afford the mononuclear Dy complex, [(NHAr*)Dy][BArF] (), with a cationic [(NHAr*)Dy] core.

An Organometallic Erbium Bismuth Cluster Complex Comprising a Bi Zintl Ion.

An organometallic erbium bismuth cluster complex, [K(THF)][Cp*ErBi] (), featuring a heterometallocubane core was isolated. The cube emerges from the rare Bi Zintl ion, bridging two erbium centers for the first time. SQUID magnetometry and calculations uncovered dominant antiferromagnetic coupling enabled through the chair-like hexabismuth anion.

Stabilization of the Compressed Planar Benzene Dianion in Inverse-Sandwich Rare Earth Metal Complexes.

For the first time, the capture of the planar antiaromatic parent benzene dianion in between two trivalent rare earth (RE) metal cations (RE), each stabilized by two guanidinate ligands, is reported. The synthesized inverse-sandwich complexes [{(MeSi)NC(NPr)}RE](μ-η : η-CH), (RE=Y (1), Dy (2), and Er (3)) were crystallized from aprotic solvents and feature a remarkably planar parent benzene dianion, previously not encountered for any metal ion prone to low or absent covalency. The -2 charge localization at the benzene ligand was deduced from the results obtained by single-crystal X-ray diffraction analyses, spectroscopy, magnetometry, and Density Functional Theory (DFT) calculations.

Isolation of Elusive Fluoflavine Radicals in Two Differing Oxidation States.

Facile access and switchability between multiple oxidation states are key properties of many catalytic applications and spintronic devices yet poorly understood due to inherent complications arising from isolating a redox system in multiple oxidation states without drastic structural changes. Here, we present the first isolable, free fluoflavine (flv) radical flv() as a bottleable potassium compound, [K(crypt-222)](flv), , and a new series of organometallic rare earth complexes [(Cp*Y)(μ-flv)]X, (where Cp* = pentamethylcyclopentadienyl, X = [Al(OC{CF})] (z = -1), ; X = 0 (z = -2), ; [K(crypt-222)] (z = -3), ) comprising the flv ligand in three different oxidation states, two of which are paramagnetic flv and flv. Excitingly, , , and constitute the first isolable flv and flv radical complexes and, to date, the only isolated flv radicals of any oxidation state.

Implementation of 2,2'-azobispyridine radical mono- and dianions in dinuclear rare earth metal complexes.

The seminal isolation of a dinuclear rare earth metal complex comprising a bridging 2,2'-azobispyridyl radical anion, [(CpY)(μ-abpy˙)](BPh), is presented, which was obtained from a one-electron chemical oxidation of [(CpY)(μ-abpy)]. The unprecedented compounds were characterized by crystallography, spectroscopy and DFT computations. The radical character was proven by EPR spectroscopy.

Construction of intermolecular σ-hole interactions in rare earth metallocene complexes using a 2,3,4,5-tetraiodopyrrolyl anion.

The generation of noncovalent intermolecular interactions represents a powerful method to control molecular vibrations and rotations. Combining these with the axial ligand field enforced by the metallocene ligand scaffold provides a dual-pronged approach in controlling the magnetic-relaxation pathways for dysprosium-based single-molecule magnets (SMMs). Here, we present the first implementation of 2,3,4,5-tetraiodopyrrole (TIPH) in its anionic form [TIP] as a ligand in three isostructural rare-earth metal complexes Cp*RE(TIP) (1-RE, RE = Y, Gd, and Dy; Cp* = pentamethylcylopentadienyl), where the TIP ligand binds through the nitrogen and one iodine atom κ(N,I) to the metal centre.

Modulation of Fe-Fe distance and spin in diiron complexes using tetradentate ligands with different flanking donors.

Here we report the synthesis and characterization of diiron complexes containing triaryl N and NS ligands derived from -phenylenediamine. The complexes display significant differences in Fe-Fe distances and magnetic properties that depend on the identity of the flanking NMe and SMe donor groups.

Introducing the Bis(mesitoyl)phosphide Ligand into Dinuclear Trivalent Rare Earth Metal Coordination Chemistry.

Anionic ancillary ligands play a critical role in the construction of rare earth (RE) metal complexes due to the large influence on the stability of the molecule and engendering emergent electronic properties that are of interest in a plethora of applications. Supporting ligands comprising oxygen donor atoms are highly pursued in RE chemistry owing to the high oxophilicity innate to these ions. The scarcely employed bis(acyl)phosphide (BAP) ligands feature oxygen coordination sites and contain a phosphide backbone rendering it attractive for RE-coordination chemistry.

Linear, Electron-Rich Erbium Single-Molecule Magnet with Dibenzocyclooctatetraene Ligands.

Judicious design of ligand scaffolds to highly anisotropic lanthanide ions led to substantial advances in molecular spintronics and single-molecule magnetism. Erbium-based single-molecule magnets (SMMs) are rare, which is attributed to the prolate-shaped Er ion requiring an equatorial ligand field for enhancing its single-ion magnetic anisotropy. Here, we present an electron-rich mononuclear Er SMM, [K(crypt-222)][Er(dbCOT)], (where dbCOT = dibenzocyclooctatetraene), that was obtained from a salt metathesis reaction of ErCl and KdbCOT.

Guanidinate Yttrium Complexes Containing Bipyridyl and Bis(benzimidazolyl) Radicals.

Ancillary ligand scaffolds that sufficiently stabilize a metal ion to allow its coordination to an open-shell ligand are scarce, yet their development is essential for next-generation spin-based materials with topical applications in quantum information science. To this end, a synthetic challenge must be met: devising molecules that enable the binding of a redox-active ligand through facile displacement and clean removal of a weakly coordinating anion. Here, we probe the accessibility of unprecedented radical-containing rare-earth guanidinate complexes by combining our recently discovered yttrium tetraphenylborate complex [{(MeSi)NC(NPr)}Y][(μ-η-Ph)(BPh)] with the redox-active ligands 2,2'-bipyridine (bpy) and 2,2'-bis(benzimidazole) (Bbim), respectively, under reductive conditions.

From an Isolable Bismolyl Anion to an Yttrium-Bismolyl Complex with μ-Bridging Bismuth(I) Centers and Polar Covalent Y-Bi Bonds.

Invited for the cover of this issue is the group of Selvan Demir at the Michigan State University. The cover art depicts the helicopter landing of the first crystallographically characterized bismolyl anion potassium salt in a desert oasis landscape with pyramids of elemental bismuth. Read the full text of the article at 10.

Isolation of an organometallic yttrium bismuth cluster and elucidation of its electronic structure.

A rare organometallic yttrium bismuth cluster complex with a heterometallocubane structure at the core was isolated and characterised by single-crystal X-ray diffraction analysis and UV-Vis spectroscopy. The anionic Bi core is best described as a Zintl ion. Computational exploration of its electronic structure reveals polarised Y-Bi bonds alongside delocalisation of the Bi-Bi bonds.

From an Isolable Bismolyl Anion to an Yttrium-Bismolyl Complex with μ-Bridging Bismuth(I) Centers and Polar Covalent Y-Bi Bonds.

The synthesis and first structural characterization of the [K(18-crown-6)] bismolyl Bi (C Me Bi) contact ion pair (1) is presented. Notably, according to Natural Resonance Theory calculations, the Bi anion of 1 features two types of leading mesomeric structures with localized anionic charge and two lone pairs of electrons at the Bi center, as well as delocalized anionic charge in the π-conjugated C Bi ring. The lone pairs at Bi enable a unique bridging coordination mode of the bismolyl ligand, as shown for the first rare earth metal bismolyl complex (Cp Y) (μ-η -Bi ) (2).

Pyrrolyl-Bridged Metallocene Complexes: From Synthesis, Electronic Structure, to Single-Molecule Magnetism.

The π- and σ-basicity of the pyrrolyl ligand affords several coordination modes. A sterically encumbering coordination sphere around metal centers may foster new coordination modes for the pyrrolyl ligand. Here, we present three dinuclear rare earth complexes [Cp*RE(μ-pyr)], [RE = Y (), La (), Dy (); Cp* = pentamethylcyclopentadienyl, pyr = pyrrolyl], which were synthesized through a protonolysis reaction between allyl complexes and H-pyrrole.

Magnetic hysteresis and large coercivity in bisbenzimidazole radical-bridged dilanthanide complexes.

A judicious combination of radical ligands innate to diffuse spin orbitals with paramagnetic metal ions elicits strong magnetic exchange coupling which leads to properties important for future technologies. This metal-radical approach aids in effective magnetic communication of especially lanthanide ions as their 4f orbitals are contracted and not readily accessible. Notably, a high spin density on the donor atoms of the radical is required for strong coupling.

A rare isocyanide derived from an unprecedented neutral yttrium(ii) bis(amide) complex.

A room temperature stable complex formulated as Y(NHAr*) has been prepared, where Ar* = 2,6-(2,4,6-(Pr)CH)CH, by KC reduction of ClY(NHAr*). Based on EPR evidence, Y(NHAr*) is an example of a d Y(ii) complex with significant delocalization of the unpaired electron density from the metal to the ligand. The isolation of molecular divalent metal complexes is challenging for rare earth elements such as yttrium.

Taming Super-Reduced Bi Radicals with Rare Earth Cations.

Here, we report the synthesis of two new sets of dibismuth-bridged rare earth molecules. The first series contains a bridging diamagnetic Bi anion, (Cp*RE)(μ-η:η-Bi), (where Cp* = pentamethylcyclopentadienyl; RE = Gd (), Tb (), Dy (), Y ()), while the second series comprises the first Bi radical-containing complexes for any d- or f-block metal ions, [K(crypt-222)][(Cp*RE)(μ-η:η-Bi)]·2THF (, RE = Gd (), Tb (), Dy (), Y (); crypt-222 = 2.2.

Linear, Electron-Rich, Homoleptic Rare Earth Metallocene and Its Redox Activity.

The first homoleptic sandwich complex of dibenzocyclooctatetraene (dbCOT), representing a large cyclooctatetraene (COT) ligand with two fused benzene moieties, for any metal was accessed through salt metathesis of YCl with KdbCOT in the presence of 2.2.2-cryptand.

Isolation of the elusive bisbenzimidazole Bbim˙ radical anion and its employment in a metal complex.

The discovery of singular organic radical ligands is a formidable challenge due to high reactivity arising from the unpaired electron. Matching radical ligands with metal ions to engender magnetic coupling is crucial for eliciting preeminent physical properties such as conductivity and magnetism that are crucial for future technologies. The metal-radical approach is especially important for the lanthanide ions exhibiting deeply buried 4f-orbitals.

Heteroleptic Rare-Earth Tris(metallocenes) Containing a Dibenzocyclooctatetraene Dianion.

Isolable heteroleptic tris(metallocenes) containing five-membered and larger rings remain extremely scarce. The utilization of tripositive rare-earth-metal ions with ionic radii >1 Å allowed access to unprecedented and sterically congested dibenzocyclooctatetraenyl (dbCOT) metallocenes, [K(crypt-222)][CpRE(η-dbCOT)] (RE = Y (), Dy (); Cp = tetramethylcyclopentadienyl), through a salt metathesis reaction involving CpRE(BPh) and the potassium salt of the dbCOT dianion. The solid-state structures were investigated by single-crystal X-ray diffraction, magnetometry, and IR spectroscopy and provided evidence for the first crystallographically characterized (dbCOT) anion in a complex containing d- or f-block metals.

A rare earth metallocene containing a 2,2'-azopyridyl radical anion.

Introducing spin onto organic ligands that are coordinated to rare earth metal ions allows direct exchange with metal spin centres. This is particularly relevant for the deeply buried 4f-orbitals of the lanthanide ions that can give rise to unparalleled magnetic properties. For efficacy of exchange coupling, the donor atoms of the radical ligand require high-spin density.

Slow Magnetic Relaxation in Mono- and Bimetallic Lanthanide Tetraimido Sulfate S(NtBu) Complexes.

Invited for the cover of this issue are Selvan Demir and co-worker from the Michigan State University at East Lansing, and Dietmar Stalke and co-workers from the Georg-August Universität at Göttingen. The image illustrates the first coordination of a tetraimido sulfate ligand via two of its nitrogen donors to a lanthanide ion producing mono- and bimetallic lanthanide complexes where specifically the dysprosium congeners, benefitting from the intrinsic oblate-shaped electron density, feature single-molecular magnet behavior as indicated by the observed slow magnetic relaxation. Read the full text of the article at 10.

Slow Magnetic Relaxation in Mono- and Bimetallic Lanthanide Tetraimido-Sulfate S(NtBu) Complexes.

Lanthanide ions are particularly well-suited for the design of single-molecule magnets owing to their large unquenched orbital angular momentum and strong spin-orbit coupling that gives rise to high magnetic anisotropy. Such nanoscopic bar magnets can potentially revolutionize high-density information storage and processing technologies, if blocking temperatures can be increased substantially. Exploring non-classical ligand scaffolds with the aim to boost the barriers to spin-relaxation are prerequisite.