Spin crossover of a Fe(II) mononuclear complex induced by intermolecular factors involving chloride and solvent ordering.

Two new salts of a mononuclear tripodal Fe(II) complex were prepared, using ClO and Cl. The ClO sample (1) remained HS at low temperatures, similar to the previously reported BF analogue. Crystallising with the Cl anion (2) led to a markedly different crystal packing arrangement, and engendered SCO activity.

Investigating the Conformations of a Family of [ML] Helicates Using Single Crystal X-ray Diffraction.

We present five new dinuclear triple helicate compounds of types [Mn](ClO), [Co](BF), [Ni](BF), [Cu](BF), and [Zn](BF), where is a previously reported semi-rigid ligand incorporating two α-diimine primary donor groups and two secondary 4-pyridyl donor groups. All complexes have been characterized in both solution and the solid state. Single crystal X-ray diffraction studies were used to probe the variation in the respective helical structures as the coordinated metal ion was altered, including the effect on the orientations of the secondary binding domains.

Highly Tunable 4-Phosphoryl Pyrazolone Receptors for Selective Rare-Earth Separation.

Highly selective rare-earth separation has become increasingly important due to the indispensable role of these elements in various cutting-edge technologies including clean energy. However, the similar physicochemical properties of rare-earth elements (REEs) render their separation very challenging, and the development of new selective receptors for these elements is potentially of very considerable economic and environmental importance. Herein, we report the development of a series of 4-phosphoryl pyrazolone receptors for the selective separation of trivalent lanthanum, europium, and ytterbium as the representatives of light, middle, and heavy REEs, respectively.

Selective Separation of Lithium, Magnesium and Calcium using 4-Phosphoryl Pyrazolones as pH-Regulated Receptors.

Ensuring continuous and sustainable lithium supply requires the development of highly efficient separation processes such as LLE (liquid-liquid extraction) for both primary sources and certain waste streams. In this work, 4-phosphoryl pyrazolones are used in an efficient pH-controlled stepwise separation of Li from Ca , Mg , Na and K . The factors affecting LLE process, such as the substitution pattern of the extractant, diluent/water distribution, co-ligand, pH, and speciation of the metal complexes involved, were systematically investigated.

Spin Crossover Induced by Changing the Identity of the Secondary Metal Ion from Pd to Ni in a Face-Centered Fe M Cubic Cage.

Discrete spin crossover (SCO) heteronuclear cages are a rare class of materials which have potential use in next-generation molecular transport and catalysis. Previous investigations of cubic cage [Fe Pd L ] constructed using semi-rigid metalloligands, found that Fe centers of the cage did not undergo spin transition. In this work, substitution of the secondary metal center at the face of the cage resulted in SCO behavior, evidenced by magnetic susceptibility, Mössbauer spectroscopy and single crystal X-ray diffraction.

Synergistic Strengthening in Graphene Oxide and Oxidized Single-walled Carbon Nanotube Hybrid Material for use as Electrolytes in Proton Exchange Membrane Fuel Cells.

Herein, we report an efficient proton exchange membrane formed from a synergistic combination of graphene oxide (GO) and oxidized single-walled carbon nanotube (CNTOX) by the freeze-drying route that gives rise to enhanced fuel cell power density. At 25 °C and 100% relative humidity (RH), the 3DGO-CNTOX hybrid shows remarkably high out-of-plane and in-plane proton conductivities of 6.64×10 and 5.

High Proton Conductivity of 3D Graphene Oxide Intercalated with Aromatic Sulfonic Acids.

The development of efficient proton conductors that are capable of high power density, sufficient mechanical strength, and reduced gas permeability is challenging. Herein, we report the development of a series of aromatic sulfonic acid/graphene oxide hybrid membranes incorporating benzene sulfonic acid (BS), naphthalene sulfonic acid (NS), naphthalene disulfonic acid (DS) or pyrene sulfonic acid (PS) using a facile freeze dried method. For out-of-plane proton conductivity, the 3DGO-BS and 3DGO-NS yielded proton conductivities of 4.

Insights at the molecular level into the formation of oxo-bridged trinuclear uranyl complexes.

Reaction of 1,3,4,6-tetra--acetyl--(2-hydroxy)-naphthylidene glucosamine (HL(Ac)) with uranyl acetate in ethanol leads to formation of dinuclear [(UO)(L)] (1). In a second step 1 is quantitatively transferred into the trinuclear oxo-bridged complex [(UO)(μ-O)(L)] (2) deprotonation and coordination of a water molecule. This transformation was followed by NMR and UV/Vis spectroscopy and it proved possible to selectively introduce O into the μ-bridge.

A Ferroelectric Metallomesogen Exhibiting Field-Induced Slow Magnetic Relaxation.

Magnetoelectric (ME) materials exhibiting coupled electric and magnetic properties are of significant interest because of their potential use in memory storage devices, new sensors, or low-consumption devices. Herein, we report a new category of ME material that shows liquid crystal (LC), ferroelectric (FE), and field-induced single molecule magnet (SMM) behaviors. Co(II) complex incorporating alkyl chains of type [Co(3C -bzimpy) ](BF ) (1; 3C -bzimpy=2,2'-(4-hexadecyloxy-2,6-diyl)bis(1-hexadecyl-1H-benzo[d]imidazole)) displayed a chiral smectic C mesophase in the temperature range 321 K-458 K, in which distinct FE behavior was observed, with a remnant polarization (88.

Engineering ferromagnetism in Ni(OH) nanosheets using tunable uniaxial pressure in graphene oxide/reduced graphene oxide.

The interlayer spaces in two dimensional (2D) layered materials such as graphene, metal oxides and metal chalcogenides can be used in a number of roles that include the trapping of gases, for ion transfer and for water purification applications. In such spaces, "inner" pressure occurs on guest species enclosed between the layers and its variation can, in principal, be used for precisely controlling particular guest properties. In this study, a mixture of two 2D materials including graphene oxide (GO) and nickel hydroxide (Ni(OH)), was employed to yield an anisotropic GO-Ni(OH) hybrid 2D sheet.

4-Phosphoryl Pyrazolones for Highly Selective Lithium Separation from Alkali Metal Ions.

Effective receptors for the separation of Li from a mixture with other alkali metal ions under mild conditions remains an important challenge that could benefit from new approaches. In this study, it is demonstrated that the 4-phosphoryl pyrazolones, HL -HL , in the presence of the typical industrial organophosphorus co-ligands tributylphosphine oxide (TBPO), tributylphosphate (TBP) and trioctylphosphine oxide (TOPO), are able to selectively recognise and extract lithium ions from aqueous solution. Structural investigations in solution as well as in the solid state reveal the existence of a series of multinuclear Li complexes that include dimers (TBPO, TBP) as well as rarely observed trimers (TOPO) and represent the first clear evidence for the synergistic role of the co-ligands in the extraction process.

Lethal Interactions of SARS-CoV-2 with Graphene Oxide: Implications for COVID-19 Treatment.

The rapid transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-driven infection signifies an ultimate challenge to global health, and the development of effective strategies for preventing and/or mitigating its effects are of the utmost importance. In the current study, an in-depth investigation for the understanding of the SARS-CoV-2 inactivation route using graphene oxide (GO) is presented. We focus on the antiviral effect of GO nanosheets on three SARS-CoV-2 strains: Wuhan, B.

Hydrogen bond-induced abrupt spin crossover behaviour in 1-D cobalt(II) complexes - the key role of solvate water molecules.

The magnetic properties and structural aspects of the 1-D cobalt(ii) complexes, [Co(pyterpy)Cl2]·2H2O (1·2H2O; pyterpy = 4'-(4'''-pyridyl)-2,2':6',2''-terpyridine) and [Co(pyethyterpy)Cl2]·2H2O (2·2H2O; pyethyterpy = 4'-((4'''-pyridyl)ethynyl)-2,2':6',2''-terpyridine) are reported. In each complex the central cobalt(ii) ion displays an octahedral coordination environment composed of three nitrogen donors from the terpyridine moiety, a nitrogen donor from a pyridyl group and two chloride ligands which occupy the axial sites. 1·2H2O exhibits abrupt spin-crossover (SCO) behaviour (T1/2↓ = 218 K; T1/2↑ = 227 K) along with a thermal hysteresis loop, while 2·2H2O and the dehydrated species 1 and 2 exhibit high-spin (HS) states at 2-300 K as well as field-induced single-molecule magnet (SMM) behaviour attributed to the presence of magnetic anisotropic HS cobalt(ii) species (S = 3/2).

Saccharified Uranyl Ions: Self-Assembly of UO into Trinuclear Anionic Complexes by the Coordination of Glucosamine-Derived Schiff Bases.

The reaction of UO (OAc)  ⋅ 2H O with the biologically inspired ligand 2-salicylidene glucosamine (H L ) results in the formation of the anionic trinuclear uranyl complex [(UO ) (μ -O)(L ) ] (1 ), which was isolated in good yield as its Cs-salt, [Cs] 1. Recrystallization of [Cs] 1 in the presence of 18-crown-6 led to formation of a neutral ion pair of type [M(18-crown-6)] 1, which was also obtained for the alkali metal ions Rb and K (M=Cs, Rb, K). The related ligand, 2-(2-hydroxy-1-naphthylidene) glucosamine (H L ) in a similar procedure with Cs gave the corresponding complex [Cs(18-crown-6)] [(UO ) (μ -O)(L ) ([Cs(18-crown-6)] 2).

Spin crossover phenomena in long chain alkylated complexes.

Soft materials represented by polymers, liquid crystals, and colloids are a class of materials that exhibit a variety of unique functionalities which derive from their non-rigid structures. In particular, soft metal complexes incorporating flexible long alkyl chains in their structures have been shown to display synergy between the structural dynamics of the long alkyl chain moieties and the electron dynamics occurring at the metal centre. This review presents a discussion of such soft metal complexes with a focus on spin crossover (SCO) behaviours that are associated with a structural phase transition, including a liquid crystal (LC) transition, arising from the flexible natures of the respective complexes.

Ferroelectric and Spin Crossover Behavior in a Cobalt(II) Compound Induced by Polar-Ligand-Substituent Motion.

Ferroelectric spin crossover (SCO) behavior is demonstrated to occur in the cobalt(II) complex, [Co(FPh-terpy) ](BPh ) ⋅3ac (1⋅3 ac; FPh-terpy=4'-((3-fluorophenyl)ethynyl)-2,2':6',2''-terpyridine) and is dependent on the degree of 180° flip-flop motion of the ligand's polar fluorophenyl ring. Single crystal X-ray structures at several temperatures confirmed the flip-flop motion of fluorobenzene ring and also gave evidence for the SCO behavior with the latter behavior also confirmed by magnetic susceptibility measurements. The molecular motion of the fluorobenzene ring was also revealed using solid-state F NMR spectroscopy.

Magnetism in a helicate complexes arising with the tetradentate ligand.

The synthesis of [M(dimphen)(NCS)] (1; M = Fe), (2; M = Co), (3; M = Mn) and [Fe(dimphen)(NCSe)] (4), where dimphen = [1,2-bis(9-methyl-1,10-phenanthrolin-2-yl)ethane], are reported. The crystal packing structures of 1-3, show intermolecular π-π stacking and NCSSCN interactions. The complex 1 shows ferromagnetic interaction, and the complex 2 displays single-molecular magnet behaviour.

Exocyclic Coordination of Thiamacrocycles Leading to - and -Palladium(II) Complexes and a Tripalladium(II) Complex Incorporating Acetimidic Anhydride.

Preferential formation of - or -palladium(II) complexes controlled via the exocyclic binding sites embedded in dithiamacrocycles ( = -S(CH)S-; = -S(CH)O(CH)S-) is reported. From the reaction with KPdCl, the shorter sulfur-to-sulfur separation in preferentially leads to the formation of -[Pd()Cl] (), while , incorporating a larger sulfur-to-sulfur separation, coordinates in a trans fashion to form a cyclic dimer, -[Pd()Cl] (). The observed results illustrate the possibility for the controlled formation of cis/trans square-planar complexes through binding-site design.

Water Molecule-Induced Reversible Magnetic Switching in a Bis-Terpyridine Cobalt(II) Complex Exhibiting Coexistence of Spin Crossover and Orbital Transition Behaviors.

The development of molecule-based switchable materials remains an important challenge in the field of molecular science. Achievement of a structural phase transition induced by adsorption/desorption of guest molecules in spin crossover (SCO) Co(II) compounds is of significant interest because of the possibility that the spin state of the magnetic anisotropic high-spin (HS, = 3/2) and low-spin (LS, = 1/2) states can be switched via the induced changes in associated intermolecular interactions. In this study, we demonstrated a reversible magnetic switching associated with spin state conversion, along with a single-crystal to single-crystal (SCSC) phase transition induced by dehydration/rehydration.

Solvent vapor-induced polarity and ferroelectricity switching.

Vapor-induced crystal to crystal transformation between non-polar [Fe(sap)(acac)(sol)] (Hsap = 2-salicylideneaminophenol, acac = acethylacetate, sol = MeOH, pyridine) and polar [Fe(sap)(acac)(DMSO)] was demonstrated. It provides an example of switchable ferroelectric behaviour attributted to the structural phase transition triggered by solvent vapour.

Solvent-Dependent Bending Ability of Salen-Derived Organic Crystals.

The formation of plastic or brittle organic crystals of salen derivatives that depend on the solvents employed for crystallization is demonstrated. Large yellow crystals (ranging from mm to cm size) of ten different salen derivatives were obtained and investigated. Among them, (bis(2-hydroxyacetophenone)ethylenediimine) 2, which was recrystallized from dichloromethane, tetrahydrofuran or chloroform, exhibited plastic deformation behaviour when mechanical force was applied to the (001) face.

Luminescent ionic liquid formed from a melted rhenium(v) cluster.

Recently, non-crystalline coordination materials have been shown to represent a versatile class of functional materials. However, such materials incorporating metal complex clusters have remained largely unexplored. Herein, we demonstrate that a luminescent tetranuclear ReV cluster melts at 489 K, with the cluster structure being maintained in the corresponding supercooled ionic liquid phase.

Double-layered honeycomb architectures constructed via hierarchical self-assembly of hexagonal spin crossover cobalt(ii) metallacycles.

A hexagonal cobalt(ii) metallacycle and its "lipid packaged" derivatives, [Co(R-bisterpy)]X (R = H, OCH, OCH; X = BF, C-Glu), have been synthesized and characterized. The compounds incorporating BF anions formed sphere-like aggregates while the compounds with C-Glu lipid anions gave double-layered honeycomb architectures composed of hexagonal stacked tubular structures, which exhibit spin crossover behaviour.

Ion conduction switching between H and OH induced by pH in graphene oxide.

Ion conduction through graphene oxide (GO) nanosheets that is pH-switchable between H (in acid) and OH (in base) ions is demonstrated. This finding is the first observation of this type for ion conductive materials and demonstrates an example of stimuli-driven ion-conduction switching.

CO -Induced Spin-State Switching at Room Temperature in a Monomeric Cobalt(II) Complex with the Porous Nature.

CO -responsive spin-state conversion between high-spin (HS) and low-spin (LS) states at room temperature was achieved in a monomeric cobalt(II) complex. A neutral cobalt(II) complex, [Co (COO-terpy) ]⋅4 H O (1⋅4 H O), stably formed cavities generated via π-π stacking motifs and hydrogen bond networks, resulting in the accommodation of four water molecules. Crystalline 1⋅4 H O transformed to solvent-free 1 without loss of porosity by heating to 420 K.