How the spin state tunes the slow magnetic relaxation field dependence in spin crossover cobalt(II) complexes.

A novel family of cobalt(II) compounds with tridentate pyridine-2,6-diiminephenyl type ligands featuring electron-withdrawing substituents of general formula [Co(-XPhPDI)](ClO)·S [-XPhPDI = 2,6-bis(-halophenylformimidoyl)pyridine with = 4 (1-3) and 3 (4); X = I (1), Br (2 and 4) and Cl (3); S = MeCN (1 and 2) and EtOAc (3)] has been synthesised and characterised by single-crystal X-ray diffraction, electron paramagnetic resonance, and static (dc) and dynamic (ac) magnetic measurements combined with theoretical calculations. The structures of 1-4 consist of mononuclear bis(chelating) cobalt(II) complex cations, [Co(-XPhPDI)], perchlorate anions, and acetonitrile (1 and 2) or ethyl acetate (3) molecules of crystallisation. This unique series of mononuclear six-coordinate octahedral cobalt(II) complexes displays both thermally-induced low-spin (LS)/high-spin (HS) transition and field-induced slow magnetic relaxation in both LS and HS states.

pH-Switching of the luminescent, redox, and magnetic properties in a spin crossover cobalt(ii) molecular nanomagnet.

The ability of mononuclear first-row transition metal complexes as dynamic molecular systems to perform selective functions under the control of an external stimulus that appropriately tunes their properties may greatly impact several domains of molecular nanoscience and nanotechnology. This study focuses on two mononuclear octahedral cobalt(ii) complexes of formula {[Co(HL)][Co(HL)L]}(ClO)·9HO (1) and [CoL]·5HO (2) [HL = 4'-(4-carboxyphenyl)-2,2':6',2''-terpyridine], isolated as a mixed protonated/hemiprotonated cationic salt or a deprotonated neutral species. This pair of pH isomers constitutes a remarkable example of a dynamic molecular system exhibiting reversible changes in luminescence, redox, and magnetic (spin crossover and spin dynamics) properties as a result of ligand deprotonation, either in solution or solid state.

A tetracobalt(II) cluster with a two vertex truncated dicubane topology endogenously supported by carboxylate-based (2-pyridyl)methylamine ligands: magneto-structural and DFT studies.

A reaction between CoCl and L-(CO) (2 : 1 stoichiometry) in CHOH affords a discrete complex [CoII4-{L-(CO)}(μ-OCH)(CHOH)(HO)Cl] (1) [L-(CO) = 3-[-{2-(pyridin-2-yl)methyl}amino]-bis(propionate)]. The structure of 1 reveals two terminal mononuclear Co{L-(CO)}Cl units connected by a dimeric CoII2(μ-OCH)(CHOH)(HO) unit present in the centre through two methoxo (μ-OCH)- and two carboxylate (μ-1,1-OCO-) bridges affording a tetranuclear coordination cluster of Co(II) with a defective dicubane topology. In 1, Co1 (terminal) has distorted octahedral CoNOCl and the central Co2 has CoO coordination.

Field-Induced Single-Ion Magnet Behavior in Nickel(II) Complexes with Functionalized 2,2':6'-2″-Terpyridine Derivatives: Preparation and Magneto-Structural Study.

Two mononuclear nickel(II) complexes of the formula [Ni(terpyCOOH)](ClO)∙4HO () and [Ni(terpyepy)](ClO) MeOH () [terpyCOOH = 4'-carboxyl-2,2':6',2″-terpyridine and terpyepy = 4'-[(2-pyridin-4-yl)ethynyl]-2,2':6',2″-terpyridine] have been prepared and their structures determined by single-crystal X-ray diffraction. Complexes and are mononuclear compounds, where the nickel(II) ions are six-coordinate by the six nitrogen atoms from two tridentate terpy moieties. The mean values of the equatorial Ni-N bond distances [2.

Misfolded α-Synuclein Assessment in the Skin and CSF by RT-QuIC in Isolated REM Sleep Behavior Disorder.

Background And Objectives: Real-time quaking-induced conversion (RT-QuIC) assay detects misfolded α-synuclein (AS) in the skin and CSF of patients with the synucleinopathies Parkinson disease and dementia with Lewy bodies. Isolated REM sleep behavior disorder (IRBD) constitutes the prodromal stage of these synucleinopathies. We aimed to compare the ability of RT-QuIC to identify AS in the skin and CSF of patients with IRBD.

Ni tetracubane cores with slow relaxation of magnetization and efficient charge utilization for photocatalytic hydrogen evolution.

We report two Ni multicubane topologies enclosed in the polyanions [Ni(OH)(WO)(PO)(B-α-PWO)]{NiW} and [Ni(OH)(HPO)(PO)(B-α-PWO)(A-α-PWO)]{NiW} that magnetically behave as Ni units clearly distinguishing them from typical Ni cubanes as shown by magnetic studies together with high field and frequency electron paramagnetic resonance (HFEPR). Beyond the unprecedented static properties, {NiW} shows the unusual coexistence of slow relaxation of the magnetization and a diamagnetic ground state ( = 0), providing the unique opportunity of studying the essentially elusive magnetic relaxation behavior in excited states. The cubane-topology dependent activity of {NiW} and {NiW} as homogeneous HER photocatalysts unveils the structural key features significant for the design of photocatalysts with efficient charge utilization exemplified by high quantum yields (QY) of 10.

Single-molecule magnet behaviour and catalytic properties of tetrahedral Co(II) complexes bearing chloride and 1,2-disubstituted benzimidazole as ligands.

Five cobalt(II) complexes of formula [CoCl(L)] [1 with L1 = 1-benzyl-2-phenyl-1-benzimidazole, 2 with L2 = 2-(furan-2-yl)-1-(furan-2-ylmethyl)-1-benzimidazole, 3 with L3 = 1-(4-chlorobenzyl)-2-(4-chlorophenyl)-1-benzimidazole, 4 with L4 = 1-(2-methoxybenzyl)-2-(2-methoxyphenyl)-1-benzimidazole and 5 with L5 = 2-(thiophen-2-yl)-1-(thiophen-2-ylmethyl)-1-benzimidazole] have been synthesised, spectroscopically characterised and cryomagnetically investigated. The crystal structures of 1, 3, 4 and 5 have been determined by X-ray diffraction on single crystals. Each cobalt(II) ion is four-coordinate in a distorted tetrahedral environment built by two chloride anions and two benzimidazole ligands.

Slow magnetic relaxation for cobalt(II) complexes in axial bipyramidal environment: an = 1/2 spin case.

A new family of magnetically mononuclear cobalt(II) complexes with formula [{Ni(L)Co(HO)(MeOH)}{Ni(L)}](ClO) where HL1 = bis(,'-bis(3-methoxysalicylidene)ethylene-1,2-diamine) (1), HL2 = bis(,'-bis(3-methoxysalicylidene)propane-1,2-diamine) (2) and [{Cu(L4)}Co](ClO) (3) where HL4 = bis(,'-bis(3-ethoxysalicylidene)cyclohexane-1,2-diamine) have been obtained employing non chiral or enantiomerically pure Schiff bases. The structural studies have been carried out by single crystal X-ray and powder diffraction. Dynamic magnetic studies indicate that some members of this family present field induced slow relaxation of the magnetization and its response has been compared with the magnetically diluted [ZnCo] complex 1D.

Data-Driven Phenotyping of Central Disorders of Hypersomnolence With Unsupervised Clustering.

Background And Objectives: Recent studies fueled doubts as to whether all currently defined central disorders of hypersomnolence are stable entities, especially narcolepsy type 2 and idiopathic hypersomnia. New reliable biomarkers are needed, and the question arises of whether current diagnostic criteria of hypersomnolence disorders should be reassessed. The main aim of this data-driven observational study was to see whether data-driven algorithms would segregate narcolepsy type 1 and identify more reliable subgrouping of individuals without cataplexy with new clinical biomarkers.

Trinuclear Cobalt(II) Triple Helicate with a Multidentate Bithiazolebis(oxamate) Ligand as a Supramolecular Nanomagnet.

The cobalt(II)-mediated self-assembly of the potentially tris(chelating) ,'-2,2'-(4,4'-bithiazole)bis(oxamate) (dabtzox) ligand gives a new metal-organic supramolecular nanomagnet of formula KCo(dabtzox)·8HO·MeOH () featuring a unique linear triple-stranded trinuclear structure of the helicate type.

Field-induced mononuclear cobalt(II) single-molecule magnet (SMM) based on a benzothiadiazole--vanillin ligand.

A unique π-conjugated benzothiadiazole--vanillin ligand (HL), characterized by single crystal X-ray diffraction and DFT calculations, has been prepared by condensation between 4-amino-benzothiadiazole (BTD) and -vanillin. Its reaction with cobalt(II) acetate afforded the complex of formula [CoL]·CHCl (1), for which the coordination environment of the cobalt centre is a distorted octahedron and the ligand acts as a monoanionic tridentate chelate in its phenolate form. Intermolecular π-π stacking interactions between the π-conjugated BTD units provide an antiferromagnetic coupling pathway, as indicated by the analysis of the dc magnetic measurements of a crystalline sample of the complex and supported by DFT type calculations.

A rare isostructural series of 3d-4f cyanido-bridged heterometallic squares obtained by assembling [Fe{HB(pz)}(CN)] and Ln ions: synthesis, X-ray structure and cryomagnetic study.

A new series of cyanido-bridged {FeLn} neutral molecular squares of general formula [Fe{HB(pz)}(CN)(μ-CN)Ln(NO)(pyim)(PhPO)]·2CHCN [Ln = Ce (1), Pr (2), Nd (3), Gd (4), Tb (5), Dy (6) and Er (7); {HB(pz)} = hydrotris(pyrazolyl)borate, pyim = 2-(1-imidazol-2-yl)pyridine and PhPO = triphenylphosphine oxide] were obtained by reacting the low-spin [Fe{HB(pz)}(CN)] species with the preformed [Ln(pyim)(NO)(pyim)(PhPO)] complex anions (generated by mixing the nitrate salt of each Ln(III) ion with pyim and PhPO molecules). Single-crystal X-ray diffraction studies show that 1-7 are isostructural compounds that crystallize in the triclinic 1̄ space group. Their crystal structures consist of centrosymmetric cyanido-bridged {FeLn} molecular squares where two [Fe{HB(pz)}(CN)] units adopt bis-monodentate coordination modes towards two [Ln(pyim)(NO)(pyim)(PhPO)] moieties.

Unexpected formation of a dodecanuclear {CoII6CuII6} nanowheel under ambient conditions: magneto-structural correlations.

We report the unique heterobimetallic dodecanuclear oxamate-based {CoII6CuII6} nanowheel obtained using an environmentally friendly synthetic protocol. The effective Hamiltonian methodology employed herein allows the rationalisation of magnetic isotropic or anisotropic metal clusters, being a significant advance for future studies of exciting properties only observed at low and ultralow temperatures.

Holmium(III) Single-Ion Magnet for Cryomagnetic Refrigeration Based on an MRI Contrast Agent Derivative.

The coexistence of field-induced blockage of the magnetization and significant magnetocaloric effects in the low-temperature region occurs in a mononuclear holmium(III) diethylenetriamine-,,',″,″-pentaacetate complex, whose gadolinium(III) analogue is a commercial MRI contrast agent. Both properties make it a suitable candidate for cryogenic magnetic refrigeration, thus enlarging the variety of applications of this simple class of multifunctional molecular nanomagnets.

Field-induced slow magnetic relaxation and magnetocaloric effects in an oxalato-bridged gadolinium(iii)-based 2D MOF.

The coexistence of field-induced slow magnetic relaxation and moderately large magnetocaloric efficiency in the supra-Kelvin temperature region occurs in the 2D compound [Gd(ox)(HO)]·4nHO (1), a feature that can be exploited in the proof-of-concept design of a new class of slow-relaxing magnetic materials for cryogenic magnetic refrigeration.

Electroswitching of the single-molecule magnet behaviour in an octahedral spin crossover cobalt(ii) complex with a redox-active pyridinediimine ligand.

Thermal-assisted spin crossover and field-induced slow magnetic relaxation coexist in the solid state for the mononuclear cobalt(ii) complex with the non-innocent 2,6-bis(N-4-methoxyphenylformimidoyl)pyridine ligand. One-electron oxidation of the paramagnetic low-spin Co ion (S = 1/2) to the diamagnetic low-spin Co ion (S = 0) leads to the electroswitching of the slow magnetic relaxation in acetonitrile solution.

Single-Ion Magnetic Behaviour in an Iron(III) Porphyrin Complex: A Dichotomy Between High Spin and 5/2-3/2 Spin Admixture.

A mononuclear iron(III) porphyrin compound exhibiting unexpectedly slow magnetic relaxation, which is a characteristic of single-ion magnet behaviour, is reported. This behaviour originates from the close proximity (≈550 cm ) of the intermediate-spin S=3/2 excited states to the high-spin S=5/2 ground state. More quantitatively, although the ground state is mostly S=5/2, a spin-admixture model evidences a sizable contribution (≈15 %) of S=3/2 to the ground state, which as a consequence experiences large and positive axial anisotropy (D=+19.

Field-induced slow magnetic relaxation in mixed valence di- and tri-nuclear Co-Co complexes.

Two novel mixed valence Co-Co complexes, namely [CoCo(L1)(ab)(mb)(HO)]·dmf (1) and [CoCo(L2)(HO)]·2HO (2) [HL1 = (E)-2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol, ab = 2-amino-butan-1-ol anion, mb = p-methyl benzoate, HL2 = 3-((2-hydroxy-3-methoxy-benzylidene)-amino)-propionic acid, and dmf = N,N-dimethyl-formamide], were synthesized and characterized by single crystal X-ray diffraction and magnetic studies at low temperature. The structure determination reveals that both complexes belong to the monoclinic system with P21/c (1) and I2/a (2) space groups. Complex 1 is a dinuclear CoCo compound with distorted octahedral cobalt centers showing different coordination environments.

Slow magnetic relaxation and water oxidation activity of dinuclear CoCo and unique triangular CoCoCo mixed-valence complexes.

Construction of efficient multifunctional materials is one of the greatest challenges of our time. We herein report the magnetic and catalytic characterization of dinuclear [CoIIICoII(HL1)2(EtOH)(H2O)]Cl·2H2O (1) and trinuclear [CoIIICoII2(HL2)2(L2)Cl2]·3H2O (2) mixed valence complexes. Relevant structural features of the complexes have been mentioned to correlate with their magnetic and catalytic properties.

Synthesis, structural characterization and electrochemical and magnetic studies of M(hfac) (M = Cu, Co) and Nd(hfac) complexes of 4-amino-TEMPO.

Three mononuclear complexes [M(hfac)x(ATEMPO)y], where M = Cu (11) and Co (12), x = y = 2; M = Nd (13), x = 4, y = 1, and two polynuclear complexes [{Cu(hfac)2(ATEMPO)}n], where n = 2 (14) and 4 (15), were obtained by the reaction of M(hfac)x (M = CuII, CoII, NdIII; x = 2, 3) with 4-amino-TEMPO (4-amino-2,2,6,6-tetramethylpiperidin-N-oxyl) in good yields and their structural, electrochemical and magnetic properties were examined. In all cases, the radical is coordinated to the metal through the amino group, except 15, and the metal ions have an octahedral geometry, except 13. Different coordination architectures of the copper complexes were obtained as a function of the stoichiometry and solvents used.

Incorporation of Cr into a Keggin Polyoxometalate as a Chemical Strategy to Stabilize a Labile {CrO} Tetrahedral Conformation and Promote Unattended Single-Ion Magnet Properties.

Polyoxometalates (POMs) provide rigid and highly symmetric coordination sites and can be used as a strategy for the stabilization of magnetic ions. Herein, we report a new member of the Keggin archetype, the Cr-centered Keggin anion [α-CrWO] (CrW), with the unusual tetrahedral coordination of Cr reported for the first time in POMs conferring unattended magnetic properties. POM chemistry has recently presented excellent examples of single-molecule and single-ion magnets (SMMs and SIMs) as well as molecular spin qubits; however, the majority of POM-based SIMs reported to date contain lanthanoid ions.

Coligand Effects on the Field-Induced Double Slow Magnetic Relaxation in Six-Coordinate Cobalt(II) Single-Ion Magnets (SIMs) with Positive Magnetic Anisotropy.

Two mononuclear cobalt(II) compounds of formula [Co(dmphen)(OOCPh)]ClO·1/2HO·1/2CHOH () and [Co(dmbipy)(OOCPh)]ClO () (dmphen = 2,9-dimethyl-1,10-phenanthroline, dmbipy = 6,6'-dimethyl-2,2'-bipyridine and HOOCPh = benzoic acid) are prepared and magnetostructurally investigated. Each cobalt(II) ion is six-coordinate with a distorted octahedral CoNO environment. The complex cations are interlinked leading to supramolecular chains () and pairs () that grow along the crystallographic -axis with racemic mixtures of (Δ,Λ)-Co units.

Influence of the pyrazine substituent on the structure and magnetic properties of dicyanamide-bridged cobalt(ii) complexes.

Substituted pyrazines were successfully used to prepare two new coordination polymers of formulas {[Co(dca)2(NH2pyz)2]·H2O}n (1) and [Co3(dca)6(HOpyz)5(H2O)2]n (2) [dca = dicyanamide, NH2pyz = 2-aminopyrazine and HOpyz = 2-hydroxypyrazine] whose structures were determined by single-crystal X-ray crystallography. The structure of 1 consists of a two-dimensional rhombus grid of cobalt(ii) ions where the dca ligand adopts the μ1,5 bridging mode with trans-positioned monodentate NH2pyz molecules completing the six-coordination around each metal ion. Compound 2 exhibits a stair-like two-dimensional structure where the intralayer connections are performed by the dca and HOpyz groups exhibiting μ1,5 and bis-monodentate coordination modes, respectively.

Magnetic Molecular Conductors Based on Bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and the Tris(chlorocyananilato)ferrate(III) Complex.

Electrocrystallization of the bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) organic donor in the presence of the [Fe(ClCNAn)] tris(chlorocyananilato)ferrate(III) paramagnetic anion in different stoichiometric ratios and solvent mixtures afforded two different hybrid systems formulated as [BEDT-TTF][Fe(ClCNAn)]·3HO () and [BEDT-TTF][Fe(ClCNAn)]·2CHCN () (An = anilato). Compounds and present unusual structures without the typical segregated organic and inorganic layers, where layers of are formed by Λ and Δ enantiomers of the anionic paramagnetic complex together with mixed-valence BEDT-TTF tetramers, while layers of are formed by Λ and Δ enantiomers of the paramagnetic complex together with dicationic BEDT-TTF dimers and monomers. Compounds and show semiconducting behaviors with room-temperature conductivities of ca.