Assembling Smallest Prussian Blue Analogs Using Chiral Hydrogen Bond-Donating Unit toward Complete Phase Transition.

Exploring methods for assembling functional materials at the molecular level may yield functional expressions derived from the assembly method. This study developed novel switchable molecular assemblies characterized by abrupt, complete phase transitions promoted via hydrogen bonding with a chiral carboxylic acid. These assemblies were prepared by aggregating discrete molecules that are unresponsive to external stimuli. Furthermore, enantiopure hydrogen-bond donor (HBD) molecules provide switchable compounds with cooperative and abrupt phase transitions, whereas the racemic mixture of the HBD provides a hydrogen-bonded one-dimensional compound with a broad and incomplete phase transition when structural disordering is observed. This study presents a novel strategy for observing metal-to-metal electron-transfer-coupled spin transitions via hydrogen-bond formation.

Physical and financial impacts caused by the COVID-19 pandemic exacerbate knee pain: A longitudinal study of a large-scale general population.

OBJECTIVES: This study aimed to evaluate the changes in knee pain, a dominant cause of physical disability, following the coronavirus disease (COVID-19) pandemic, and to identify factors affecting the changes in knee pain. METHODS: We analysed the pre- and post-COVID-19 longitudinal data set of the Nagahama Study. Knee pain was assessed using the Knee Society Score (KSS). The estimated KSS from the age and sex using regression model in the pre- and post-COVID-19 data set was compared. Factors including the activity score, educational level, and various impacts of COVID-19 were analysed for correlation analyses with changes in KSS. RESULTS: Data collected from 6409 participants showed statistically significant differences in KSS, pre- (mean = 22.0; SD = 4.4) and post-COVID-19 (mean = 19.5; SD = 6.4). Low activity score (p = .008), low educational level (p < .001), and undesirable financial impact (p = .030) were independently associated with knee pain exacerbation. CONCLUSION: The harmful effects of the COVID-19 pandemic on knee pain were suggested. People should be encouraged to engage in physical activities, such as walking, despite the state of emergency. Furthermore, social support for economically disadvantaged groups may improve healthcare access, preventing the acute exacerbations of knee pain.

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(3C16 -bzimpy)2 ](BF4 )2 (1; 3C16 -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 (88.3 nC cm-2 ). Complex 1 also exhibited field-induced slow magnetic relaxation behavior that reflects the large magnetic anisotropy of the Co(II) center. Furthermore, the dielectric property of 1 was able to be tuned by an external magnetic field occurring from both spin-lattice coupling and molecular orientational variation. Clearly, this multifunctional compound, combining LC, FE, and SMM properties, represents an entry to the development of a range of next-generation ME materials.

Magnetic Phase Switching Performance in an Fe-Tetraoxolene-Layered Metal-Organic Framework via Electrochemical Cycling.

The iron-based tetraoxolene honeycomb-layered compound (NPr4)2[Fe2(Cl2An)3] (1; NPr4+ = tetrapropylammonium cation; Cl2An2- = 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinonate) was used as the cathode material for lithium-ion batteries. We observed a charge-cycling performance (∼16 times) with three electrons/Li+ ion insertion and extraction, corresponding to the stoichiometry redox of Cl2An2- + e- ↔ Cl2An·3- and Fe3+ + e- ↔ Fe2+. The generation/annihilation of radicals, Cl2An·3-, enables the significant improvement/deterioration of the magnetic phase transition temperature with Tc = 100 K.

Ionicity Diagrams for Electron-Donor and -Acceptor Metal-Organic Frameworks: DA Chains and D2A Layers Obtained from Paddlewheel-Type Diruthenium(II,II) Complexes and Polycyano-Organic Acceptors.

Recent developments in research concerning metal-organic frameworks and coordination polymers have provided the successful design of charge-variable molecular frameworks. However, few comprehensive studies exist that investigate the control of charge states in series of molecular frameworks such as these. Herein, we discuss the ionicity diagrams of two series containing electron-donor (D) and -acceptor (A) units: one-dimensional DA chains and two-dimensional D2A layers. The series were obtained by reacting paddlewheel-type diruthenium(II,II) complexes ([Ru2II,II]), which served as D units, with the polycyano-organic acceptors N,N'-dicyanoquinodiimine (DCNQI) and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), which served as A units. Fifteen novel members of neutral charged DA chains were fabricated in this study to characterize the ionicity diagrams for DA and D2A systems.

Engineering ferromagnetism in Ni(OH)2 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)2), was employed to yield an anisotropic GO-Ni(OH)2 hybrid 2D sheet. The inner pressure associated with this material was able to be tuned by reduction of the GO (to yield rGO) and this in turn was shown to affect the magnetic behaviour of Ni(OH)2. The ferromagnetic transition temperature (Tc) for Ni(OH)2 decreases as the interlayer distance became shorter, which is opposite to the behaviour observed for the application of hydrostatic pressure to the hybrid sheet. The uniaxial pressure affecting the interlayer of the 2D material, and generated by the reduction of GO to rGO, has the potential to not only influence the behaviour of a range of magnetic materials, but also individual properties of other types of functional materials.

Solid-State Hydrogen-Bond Alterations in a [Co2 Fe2 ] Complex with Bifunctional Hydrogen-Bonding Donors.

A hydrogen-bonding donor-acceptor system, [Co2 Fe2 (bpy*)4 (CN)6 (tp*)2 ](PF6 )2 ⋅2ABA⋅4BN⋅2PE (1 solv ), was prepared by co-crystallization of an external stimuli-responsive cyanide-bridged tetranuclear [Co2 Fe2 ] complex and bifunctional hydrogen-bonding donors, p-aminobenzoic acid. Compound 1 solv exhibited a gradual electron-transfer-coupled spin transition (ETCST), and the removal of solvent molecules led to an abrupt thermal ETCST behavior with increased transition temperature. X-ray structural analysis revealed that the modification of ETCST was caused by a significant alteration of a hydrogen-bonding mode between the tetranuclear [Co2 Fe2 ]2+ cations and ABA molecules. Variable temperature IR measurements indicated that the desolvated form, 1 desolv , showed dynamic alteration of hydrogen-bonding interactions coupled with thermal ETCST behavior. These results suggested that the tetranuclear [Co2 Fe2 ] complex shows solid-state modulations of hydrogen-bond strengths by external stimuli.

Intramolecular Electron Transfers in a Series of [Co2Fe2] Tetranuclear Complexes.

Discrete cyanide-bridged Co-Fe multinuclear complexes can be considered as functional units of bulk Co-Fe Prussian blue analogues, and they have been recognized as a new class of switching molecules in the last decade. The switching property of the cyanide-bridged Co-Fe complexes is based on intramolecular electron transfers between Co and Fe ions, and we herein refer to this phenomenon as an electron transfer-coupled spin transition (ETCST). Although there have been numerous reports on the complexes exhibiting ETCST behavior, the systematic study of the substituent effects on the thermal ETCST equilibrium in solution has not been reported yet, and the rational control of the equilibrium temperature remains challenging. We report here the syntheses and thermal ETCST behavior both in the solid state and solution for a series of tetranuclear [Co2Fe2] complexes, [Co2Fe2(CN)6(L1)2(L2)4]X2 (L1 and L2: tri- and bidentate capping ligands for Fe and Co ions, X: counteranions). All complexes showed thermal ETCST equilibrium between high-spin ([(hs-CoII)2(ls-FeIII)2]) and low-spin ([(ls-CoIII)2(ls-FeII)2]) states in butyronitrile, and the equilibrium temperatures (T1/2) showed systematic shifts by chemical modifications and chemical stimuli. The T1/2 values were correlated with the redox potential differences (ΔE) of the Fe and Co ions in the constituent units, and the larger ΔE values led to the lower T1/2. The present result suggests that the thermal ETCST behavior in solution can be rationally designed by considering the redox potentials of the constituent molecules.

Ionic Donor-Acceptor Chain Derived from an Electron-Transfer Reaction of a Paddlewheel-Type Diruthenium(II,†II) Complex and N,N'-Dicyanoquinonediimine.

A new ionic donor-acceptor (D+ A- ) chain compound, [{Ru2 (2,6-(CF3 )2 PhCO2 )2 (p-PhPhCO2 )2 }DMDCNQI] (1; 2,6-(CF3 )2 PhCO2- =2,6-bis(trifluoromethyl)benzoate; p-PhPhCO2- =4-biphenylcarboxylate; DMDCNQI=2,5-dimethyl-N,N'-dicyanoquinonediimine) was isolated and structurally characterized. It represents the first of this type of ionic chain compounds.

One-Dimensional Chains of Paddlewheel-Type Dichromium(II,II) Tetraacetate Complexes: Study of Electronic Structure Influenced by σ- and π-Donation of Axial Linkers.

Paddlewheel-type carboxylate-bridged dichromium(II,II) complexes possess intriguing properties such as high redox activity and thermally assisted paramagnetism. However, the relationship of their structures with electronic states and physical properties has not been extensively studied. In this work, we investigated a series of one-dimensional chain complexes based on the paddlewheel-type dichromium(II,II) tetraacetate complex ([Cr2II,II(OAc)4] = [Cr2II,II]) with pyridine/pyrazine-type organic linkers (µ2-Lax) having different σ- and π-donating abilities to clarify the electronic structure of [Cr2II,II] assemblies. The chain compounds are stable in air, probably owing to their robust polymerized forms. X-ray crystallographic studies and magnetic measurements revealed that the basicity (p Kb) of Lax, which quantitatively correlates with the σ-donor strength of Lax, modulates the Cr-Cr and Cr-Lax distances and the energy separation ( ES-T) between the diamagnetic (singlet) and thermally populated paramagnetic (triplet) states. The Cr-Cr and Cr-Lax distances are strongly influenced by σ- and π-donation from Lax, while the frontier δ orbital makes only a small contribution to the structural features. Density functional theory calculations were conducted to clarify this issue. The calculations produced the following unanticipated results against the long-known model: (i) the σ bonding orbital is the HOMO and dominates bonding in the [Cr2II,II] unit, (ii) the total Cr-Cr bond order is less than 1.0, and (iii) the δ orbital electron density is almost completely localized on the chromium sites. The computational results accurately predict the magnetic behavior and provide evidence for a new configuration of frontier orbitals in [Cr2II,II(RCO2)4(Lax)2].

Thermally Induced Valence Tautomeric Transition in a Two-Dimensional Fe-Tetraoxolene Honeycomb Network.

A novel tetraoxolene-bridged Fe two-dimensional honeycomb layered compound, (NPr4 )2 [Fe2 (Cl2 An)3 ] ⋅2 (acetone)⋅H2 O (1), where Cl2 Ann- =2,5-dichloro-3,6-dihydroxy-1,4-benzoquinonate and NPr4+ =tetrapropylammonium cation, has been synthesized. 1 revealed a thermally induced valence tautomeric transition at T1/2 =236 K (cooling)/237 K (heating) between Fem+ (m=2 or 3) and Cl2 Ann- (n=2 or 3) that induced valence modulations between [FeIIHS FeIIIHS (Cl2 An2- )2 (Cl2 An.3- )]2- at T>T1/2 and [FeIIIHS FeIIIHS (Cl2 An2- )(Cl2 An.3- )2 ]2- at T

Dimensionally Controlled Assembly of an External Stimuli-Responsive [Co2 Fe2 ] Complex into Supramolecular Hydrogen-Bonded Networks.

A stimuli-responsive tetranuclear complex was assembled into new aggregates with controllable dimensionality through directional hydrogen bonds (HBs). A cyanide-bridged tetranuclear complex cation, [Co2 Fe2 (CN)6 (tp*)2 (bpy*)4 ]2+ (abbreviated to 12+ ) (tp*=hydrotris(3,5-dimethylpyrazol-1-yl)borate and bpy*=4,4'-di-methyl-2,2'-bipyridine) has two terminal cyanide nitrogens and acts as a hydrogen-bond acceptor (HBA) with a linear bridging mode. Co-crystallization of 12+ with p-hydroquinone (H2 Q), a hydrogen-bond donor (HBD) with two donor sites, led to a one-dimensional aggregate, 1(BPh4 )2 ⋅(H2 Q)⋅2 H2 O (2), while a two-dimensional sheet with a honeycomb structure, 13 (PF6 )6 ⋅(H3 PG)2 ⋅4 CH3 CN⋅8 H2 O (3), was obtained by co-crystallization with phloroglucinol (H3 PG) acting as a three-way structure-directing HBD. Magnetic measurements revealed that 2 and 3 exhibited thermal and light-induced electron-transfer-coupled spin transitions (ETCSTs).

A Hydrogen-Bonded Cyanide-Bridged [Co2 Fe2 ] Square Complex Exhibiting a Three-Step Spin Transition.

Co-crystallization of a cyanide-bridged tetranuclear complex [Co2 Fe2 ] with 4-cyanophenol (CP) gave a hydrogen bonding donor-acceptor system, [Co2 Fe2 (bpy*)4 (CN)6 (tp*)2 ](PF6 )2 ⋅2 CP⋅8 BN (1). 1 exhibited a three-step phase transition between HT, IM1, IM2, and LT phases upon temperature variation. Variable temperature magnetic measurements and structural analyses revealed that the three-step spin transition is caused by electron-transfer-coupled spin transitions (ETCSTs) accompanied with alteration of the hydrogen bonding interactions.

Cyanide-bridged decanuclear cobalt-iron cage.

A cyanide-bridged decanuclear [Co6Fe4] cluster was synthesized by a one-pot reaction, and the magnetic properties and electronic configuration were investigated. The complex displayed thermally controlled electron-transfer-coupled spin transition (ETCST) behavior between Co(III) low-spin-NC-Fe(II) low-spin and Co(II) high-spin-NC-Fe(III) low-spin states, as confirmed by single-crystal X-ray, magnetic, and Mössbauer analyses.

Solvation/desolvation induced reversible distortion change and switching between spin crossover and single molecular magnet behaviour in a cobalt(II) complex.

Coexistence and switching between spin-crossover (SCO) and single molecular magnet (SMM) behaviours in one single complex may lead to materials that exhibit bi-stable and stimuli sensitive properties in a wide temperature range and under multiple conditions; unfortunately, the conflict and dilemma in the principle of approaching SCO and SMM molecules make it particularly difficult; at low temperature, low spin (LS) SCO molecules possess highly symmetrical geometry and isotropic spins, which are not suitable for SMM behaviour. Herein, we overcome this issue by using a rationally designed Co(II) mononuclear complex [Co(MeOphterpy)2] (ClO4)2 (1; MeOphterpy = 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine), the magnetic properties of which reversibly respond to desolvation and solvation. The solvated structure reinforced a low distortion of the coordination sphere via hydrogen bonding between ligands and methanol molecules, while in the desolvated structure a methoxy group flipping occurred, increasing the distortion of the coordination sphere and stabilising the HS state at low temperature, which exhibited a field-induced slow magnetic relaxation, resulting in a reversible switching between SCO and SMM properties within one molecule.

Engineering Zeolitic-Imidazolate-Framework-Derived Mo-Doped Cobalt Phosphide for Efficient OER Catalysts.

Designing a cheap, competent, and durable catalyst for the oxygen evolution reaction (OER) is exceedingly necessary for generating oxygen through a water-splitting reaction. In this project, we have designed a ZIF-67-originated molybdenum-doped cobalt phosphide (CoP) using a simplistic dissolution-regrowth method using Na2MoO4 and a subsequent phosphidation process. This leads to the formation of an exceptional hollow nanocage morphology that is useful for enhanced catalytic activity. Metal-organic frameworks, especially ZIF-67, can be used both as a template and as a metal (cobalt) precursor. Molybdenum-doped CoP was fabricated through a two-step synthesis process, and the fabricated Mo-doped CoP showed excellent catalytic activity during the OER with a lower value of overpotential. Furthermore, the effect of the Mo amount on the catalytic activity has been explored. The best catalyst (CoMoP-2) showed an onset potential of around 1.49 V at 10 mA cm-2 to give rise to a Tafel slope of 62.1 mV dec-1. The improved catalytic activity can be attributed to the increased porosity and surface area of the resultant catalyst.

Coupling Dielectric Functionality with Magnetic Properties in Coordination Metal Complexes.

Significant research has been conducted on molecular ferroelectric materials, including pure organic and inorganic compounds; however, studies on ferroelectric materials based on coordination metal complexes are scarce. Ferroelectric materials based on coordination metal complexes have tunable structures and designs, with coexistence or synergy between the ferroelectric behavior and magnetic properties. Compared to inorganic compounds, few coordination metal complexes exhibit coupling between the magnetic and dielectric properties. Coordination metal complexes with strong coupling between the magnetic and dielectric properties exhibit dielectric permittivity variations under external magnetic fields. Therefore, they have attracted substantial interest for their potential use in magnetoelectric devices. In this review, we discuss recent advances in coordination metal complexes, that exhibit coupled magnetic functionalities and ferroelectricity or dielectric properties, including single-molecule magnets, electron delocalization systems, and external stimuli responsive compounds.

Thermally stable proton conductivity from nanodiamond oxide.

Herein, we report nanodiamond oxide (NDOx), obtained from modified Hummers' oxidation of nanodiamond (ND), showing excellent proton conductivity and thermal stability. NDOx possesses hydrophilicity resulting in higher water adsorption and the retention of functional groups at elevated temperatures can be attributed to the high proton conductivity and thermal stability, respectively.

Correction: SARS-CoV-2 suppression depending on the pH of graphene oxide nanosheets.

[This corrects the article DOI: 10.1039/D3NA00084B.].

SARS-CoV-2 suppression depending on the pH of graphene oxide nanosheets.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) inactivation of pH-dependent graphene oxide (GO) nanosheets is presented. The observed virus inactivation using an authentic virus (Delta variant) and different GO dispersions at pH 3, 7, and 11 suggests that the higher pH of the GO dispersion yields a better performance compared to that of GO at neutral or lower pH. The current findings can be ascribed to the pH-driven functional group change and the overall charge of GO, favorable for the attachment between GO nanosheets and virus particles.