Plant-Mediated Synthesis of Magnetite Nanoparticles with Aqueous Extract.

Magnetite nanoparticles (NPs) possess properties that make them suitable for a wide range of applications. In recent years, interest in the synthesis of magnetite NPs and their surface functionalization has increased significantly, especially regarding their application in biomedicine such as for controlled and targeted drug delivery. There are several conventional methods for preparing magnetite NPs, all of which mostly utilize Fe(iii) and Fe(ii) salt precursors.

Light-Induced Intramolecular Electron Transfer in a 1D [CuFe] Coordination Polymer Containing the [Fe(CO)] Core.

A one-dimensional (1D) ladder-like coordination polymer {NH[{Cu(bpy)}(CO)Fe(CO)]·HO} (; bpy = 2,2'-bipyridine) containing [Cu(bpy)(μ-CO)Cu(bpy)] cationic units linked by oxalate groups of [Fe(CO)] building blocks was investigated as a new type of photoactive solid-state system. It exhibits a photocoloration effect when exposed to direct sunlight or UV/vis irradiation. The photochromic properties and mechanism were studied by powder and single-crystal X-ray diffraction, UV/vis diffuse reflectance, IR and electron paramagnetic resonance spectroscopy, magnetization and impedance measurements, and density functional theory calculations.

Enhancement of weak ferromagnetism, exotic structure prediction and diverse electronic properties in holmium substituted multiferroic bismuth ferrite.

Bismuth ferrite (BFO, BiFeO), exhibiting both ferromagnetic and ferroelectric properties at room temperature, is one of the most researched multiferroic materials with a growing number of technological applications. In the present study, using a combined theoretical-experimental approach, we have investigated the influence of Ho-doping on the structural, electronic and magnetic properties of BFO. Synthesis and structural XRD characterization of BiHoFeO ( = 0.

Structure-Related Evolution of Magnetic Order in Anisidinium Tetrachlorocuprates(II).

Tetrachlorocuprate(II) hybrids of the three anisidine isomers (-, -, and -, or 2-, 3-, and 4-methoxyaniline, respectively) were prepared and studied in the solid state via X-ray diffraction and magnetization measurements. Depending on the position of the methoxy group of the organic cation, and subsequently, the overall cation geometry, a layered, defective layered, and the structure comprising discrete tetrachlorocuprate(II) units were obtained for the -, -, and -anisidinium hybrids, respectively. In the case of layered and defective layered structures, this affords quasi-2D-layered magnets, demonstrating a complex interplay of strong and weak magnetic interactions that lead to the long-range ferromagnetic (FM) order.

High Proton Conductivity of Magnetically Ordered 2D Oxalate-Bridged [MnCr] Coordination Polymers with Irregular Topology.

Two heterometallic coordination polymers {[NH(CH)(CH)][MnClCr(CO)]} () and {[NH(CH)-(CH)][MnClCr(CO)]} () were obtained by slow evaporation of an aqueous solution containing the building block [A][Cr(CO)] [A = (CH)(CH)NH or (CH)(CH)NH] and MnCl·2HO. The isostructural compounds comprise irregular two-dimensional (2D) oxalate-bridged anionic layers [MnClCr(CO)] with a Shubnikov plane net topology designated as (4·8), interleaved by the hydrogen-bonded templating cations (CH)(CH)NH () or (CH)(CH)NH (). They exhibit remarkable humidity-sensing properties and very high proton conductivity at room temperature [1.

Low-Dimensional Magnetism in Multivariate Copper/Zinc MOF-74 Materials Formed via Different Mechanochemical Methods.

MOF-74 is an archetypal magnetic metal-organic framework (MOF) family, with metal nodes bridged by 2,5-dioxido-1,4-benzenedicarboxylic acid (Hdobdc) and arranged into one of the simplest representations of the 1D Ising magnetic model. Recently, a novel mechano-synthetic approach opened a pathway toward a series of bimetallic multivariate (1:1) M1M2-MOF-74 materials, with the uniform distribution of metal cations in the oxometallic chains, offering a unique opportunity to investigate low-dimensional magnetism in these heterometallic MOFs. We explore here how different mechanochemical procedures affect the interaction between the metal nodes of the model system of three multivariate copper(II)/zinc(II)-MOF-74 materials, two of which were obtained through a template-controlled procedure, and the third one was obtained by recently developed mechanical MOF-alloying combined with subsequent accelerated aging.

Oxalate-based [CuCr] coordination compounds affected by the tridentate ligand, simple anion, and reactant ratio: structural and magnetic features.

Seven novel oxalate-based [CuCr] compounds: [Cu(terpy)Cl][Cr(CO)]·9HO (1; terpy = 2,2':6',2''-terpyridine), {[CrCu(HO)(terpy)(CO)]·10HO} (2), [CrCu(HO)(terpy)(CO)]·12HO (3), [Cu(HO)(terpy)][CrCu(HO)(terpy)(CO)]·9HO (4), [Cu(HO)(terpy)(NO)][CrCu(HO)(terpy)(CO)]·6HO (5), [CrCu(terpy)(CO)(NO)]·1.5HO·CHOH (6) and [CrCu(HO)(terpy)(CO)][CrCu(terpy)(CO)]·9HO·CHOH (7) were obtained from the reaction of an aqueous solution of the building block [Cr(CO)] and a methanol solution containing Cu ions and terpyridine ligand by the layering technique. Interestingly, changing only the anion of the starting salt of copper(II), NO instead of Cl, resulted in an unexpected modification in the bridge type, namely oxalate (compounds 2-7) chloride (compound 1).

A mononuclear iron(III) complex with unusual changes of color and magneto-structural properties with temperature: synthesis, structure, magnetization, multi-frequency ESR and DFT study.

From the reaction of 2-hydroxy-6-methylpyridine (L) with iron(II) tetrafluoroborate, a new mononuclear iron(III) octahedral complex [FeL](BF) has been isolated. The color of the complex reversibly changed from red at room temperature to yellow-orange at the liquid nitrogen temperature. Magnetization measurements indicate that iron(III) in [FeL](BF) is in a high-spin state = 5/2, from room temperature to 1.

Transition from High-Entropy to Conventional Alloys: Which Are Better?

The study of the transition from high-entropy alloys (HEAs) to conventional alloys (CAs) composed of the same alloying components is apparently important, both for understanding the formation of HEAs and for proper evaluation of their potential with respect to that of the corresponding CAs. However, this transition has thus far been studied in only two types of alloy systems: crystalline alloys of iron group metals (such as the Cantor alloy and its derivatives) and both amorphous (a-) and crystalline alloys, TE-TL, of early (TE = Ti, Zr, Nb, Hf) and late (TL = Co, Ni, Cu) transition metals. Here, we briefly overview the main results for the transition from HEAs to CAs in these alloy systems and then present new results for the electronic structure (ES), studied with photoemission spectroscopy and specific heat, atomic structure, thermal, magnetic and mechanical properties of a-TE-TL and Cantor-type alloys.

Humidity-Sensing Properties of an 1D Antiferromagnetic Oxalate-Bridged Coordination Polymer of Iron(III) and Its Temperature-Induced Structural Flexibility.

A novel one-dimensional (1D) oxalate-bridged coordination polymer of iron(III), {[NH(CH)(CH)][FeCl(CO)]} (), exhibits remarkable humidity-sensing properties and very high proton conductivity at room temperature (2.70 × 10 (Ω·cm) at 298 K under 93% relative humidity), in addition to the independent antiferromagnetic spin chains of iron(III) ions bridged by oxalate groups ( = -7.58(9) cm).

Structural Behavior and Spin-State Features of BaAlO Scaled through Tuned Co Doping.

Pure and Co-doped BaAlO [Ba(AlCo)O, = 0, 0.0077, 0.0379] powder samples were prepared by a facile hydrothermal route.

Magnetoelectric Multiferroicity and Magnetic Anisotropy in Guanidinium Copper(II) Formate Crystal.

Hybrid metal-organic compounds as relatively new and prosperous magnetoelectric multiferroics provide opportunities to improve the polarization, magnetization and magneto-electric coupling at the same time, which usually have some limitations in the common type-I and type-II multiferroics. In this work we investigate the crystal of guanidinium copper (II) formate [C(NH2)3]Cu(HCOO)3 and give novel insights concerning the structure, magnetic, electric and magneto-electric behaviour of this interesting material. Detailed analysis of crystal structure at 100 K is given.

Structural, Electrical, and Magnetic Versatility of the Oxalate-Based [CuFe] Compounds Containing 2,2':6',2″-Terpyridine: Anion-Directed Synthesis.

The heterodimetallic [CuFe] compounds [Cu(terpy)Cl][Fe(CO)]·10HO (;terpy = 2,2':6',2''-terpyridine), [Cu(HO)(terpy)(CO)][CuFe(CHOH)(terpy)(CO)] (), and {[CuFe(HO)(terpy)(CO)]·6HO} () were obtained using building block approach, from reaction of aqueous solution of [Fe(CO)] and a methanol solution containing Cu ions and terpy by the layering technique. Interestingly, by changing only the anion of the starting salt of copper(II), Cu(NO)·3HO instead of CuCl·2HO, an unexpected change in the type of bridge, oxalate ( and ) versus chloride (), was achieved, thus affecting the overall structural architecture. Two polymorphs of 3D coordination polymer [CuFe(HO)(terpy)(CO)] (), crystallizing in the triclinic () and monoclinic () space groups, were formed hydrothermally, depending on whether CuCl·2HO or Cu(NO)·3HO was added to the water, besides K[Fe(CO)]·3HO and terpy, respectively.

Magnetic and Electrical Behaviors of the Homo- and Heterometallic 1D and 3D Coordination Polymers Based on the Partial Decomposition of the [Cr(CO)] Building Block.

One-dimensional (1D) oxalate-bridged homometallic {[Mn(bpy)(CO)]·1.5HO} () (bpy = 2,2'-bipyridine) and heterodimetallic {[CrCu(bpy)(CHOH)(HO)(CO)][Cu(bpy)Cr(CO)]·CHCl·CHOH·HO} () coordination polymers, as well as the three-dimensional (3D) heterotrimetallic {[CaCrCu(phen)(CO)]·4CHCN·2HO} () (1,10-phenanthroline) network, have been synthesized by a building block approach using a layering technique, and characterized by single-crystal X-ray diffraction, infrared (IR) and impedance spectroscopies and magnetization measurements. During the crystallization process partial decomposition of the tris(oxalate)chromate(III) happened and 1D polymers and were formed.

Magnetic oxygen stored in quasi-1D form within BaAlO lattice.

Inorganic materials that enable a link between the storage and release of molecular oxygen offer a fertile ground in continuous quest for the applications that can potentially reduce energy consumption and thus minimize adverse effects on the environment. Herein, we address reversible intake/release of an oxygen within the BaAlO material as evidenced by unexpected magnetic ordering. Magnetic measurements unveil that an oxygen is stored in the form of condensed matter, creating a kind of low dimensional, chain-like assembly within the tunnels of BaAlO structure.

Ladder-like [CrCu] coordination polymers containing unique bridging modes of [Cr(CO)] and CrO.

Three heterometallic one-dimensional (1D) coordination polymers {A[CrCu(bpy)(CO)]·HO} [A = K (1) and NH (2); bpy = 2,2'-bipyridine] and [(CrO)Cu(CO)(phen)] (3; phen = 1,10-phenanthroline) with uncommon topology have been synthesized using a building block approach and characterized by single-crystal X-ray diffraction, IR and impedance spectroscopies, magnetization measurements, and DFT calculations. Due to the partial decomposition of the building block [Cr(CO)], all three compounds contain oxalate-bridged [Cu(L)(μ-CO)] units [L = bpy (1 and 2) and phen (3)]. In compounds 1 and 2 these cations are mutually connected through oxalate groups from [Cr(CO)], thus forming ladder-like topologies.

From a square core to square opening: structural diversity and magnetic properties of the oxo-bridged [CrNb] complexes.

Three heterometallic oxo-bridged compounds, [Cr(phen)(μ-O)Nb(CO)]·2HO (1; phen = 1,10-phenanthroline), [Cr(terpy)(HO)(μ-O)Nb(CO)]·4HO (2; terpy = 2,2';6',2''-terpyridine) and [Cr(terpy)(CO)(HO)][Cr(terpy)(CO)(μ-O)Nb(CO)]·3HO (3), have been synthesized using a building block approach and characterized by IR spectroscopy, single-crystal and powder X-ray diffraction, magnetization measurements, and DFT calculations. The molecular structures of 1 and 2, crystallizing in P422 and P2/n space groups, respectively, contain a square-shaped {Cr(μ-O)Nb} unit, while that of complex salt 3 (P1[combining macron] space group) consists of a mononuclear cation containing Cr and trinuclear anions in which two Cr ions are bridged by a -O-Nb-O- fragment. Besides hydrogen-bonding patterns resulting in a 1D- or 3D-supramolecular arrangement in 1-3, an unusual intermolecular contact has been noticed between parallel oxalate moieties occurring due to the electrostatic attraction of electron-rich carbonyl oxygen and severely electron-depleted carbon atoms in the crystal packing of 2.

The influence of metal centres on the exchange interaction in heterometallic complexes with oxalate-bridged cations.

The reaction of bis(phenanthroline)metal(ii) cations (M = Mn, Co, Ni, Cu and Zn) with bis(oxalato)chromium(iii) anions in a water/ethanol solution gives rise to a series of compounds with oxalate-bridged cations, [{M(phen)}(μ-CO)][Cr(phen)(CO)]·4HO [MnCr (1), CoCr (2), NiCr (3), CuCr (4) and ZnCr (5)]. Their structural analysis reveals that all the prepared compounds crystallize in the triclinic system, space group P1[combining macron], having similar unit cell parameters, molecular structures and crystal packing features. All metal centres in 1-5 are octahedrally coordinated: M in homodinuclear cations are coordinated with two phen molecules and one bridging oxalate ligand; Cr in anions is coordinated with one phen ligand and two bidentate oxalate groups.

Experimental and Theoretical Investigation of the Anti-Ferromagnetic Coupling of Cr Ions through Diamagnetic -O-Nb-O- Bridges.

The synthesis and properties of a novel hetero-tetranuclear compound [Cr(bpy)(μ-O)Nb(CO)]·3HO (1; bpy = 2,2'-bipyridine), investigated by single-crystal X-ray diffraction, magnetization measurements, IR, UV/visible spectroscopy, electron paramagnetic resonance (EPR; X- and Q-bands and high-field), and density functional theory (DFT) calculations, are reported. Crystal structure of 1 (orthorhombic Pcab space group) consists of a square-shaped macrocyclic {Cr(μ-O)Nb} core in which Cr and Nb ions are alternately bridged by oxo ions and three uncoordinated water molecules. The intramolecular Cr···Cr distances through the -O-Nb-O- bridges are 7.

Effect of the Cation Distribution and Microstructure on the Magnetic Behavior of the CoMnO Oxide.

The sizes of CoMnO nanoparticles can easily be tuned, from 40 to 8 nm, depending on the temperature of decomposition of the single-source molecular precursor {[Co(bpy)][Mn(CO)]·HO}. The structural features of the CoMnO spinel are also affected by the heat treatment temperature, showing a pronounced expansion of unit cell parameters as a consequence of thermally induced cation redistribution between tetrahedral and octahedral sites. Moreover, the magnetic behavior of CoMnO was successfully tailored as well; depending on the heat treatment, it is possible to switch between the superparamagnetic and ferrimagnetic ordering and to tailor the magnetic transition temperatures, i.

Magnetic order in a novel 3D oxalate-based coordination polymer {[Cu(bpy)3][Mn2(C2O4)3]·H2O}n.

A heterometallic coordination polymer {[Cu(bpy)3][Mn2(C2O4)3]·H2O}n (1; bpy = 2,2'-bipyridine) was synthesized using a building-block approach and characterized by IR spectroscopy, single-crystal X-ray diffraction, magnetization measurement, and X-band ESR spectroscopy both on a single crystal and a polycrystalline sample. The molecular structure of 1 is made of a three-dimensional (3D) anionic network [Mn2(C2O4)3]n(2n-) and tris-chelated cations [Cu(bpy)3](2+) occupying the vacancies of the framework. In compound 1 magnetic order is confirmed below 12.

A 3D oxalate-based network as a precursor for the CoMn₂O₄ spinel: synthesis and structural and magnetic studies.

A novel heterometallic oxalate-based compound of the formula {[Co(bpy)3][Mn2(C2O4)3]·H2O}n (1; bpy = 2,2'-bipyridine) was synthesized and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction (XRD), and magnetization measurement. The molecular structure of 1 is made of a three-dimensional (3D) anionic network, [Mn2(C2O4)3]n(2n-), and tris-chelated cations [Co(bpy)3](2+) occupying the vacancies of the framework. Splitting between the zero-field-cooled (ZFC) and field-cooled (FC) branches of susceptibility below the small peak at 13 K indicates magnetic ordering.

Crystal structures and magnetic properties of a set of dihalo-bridged oxalamidato copper(II) dimers.

A set of four copper(ii) complexes, and (X = Cl, Br; = N-(l-leucine methyl ester)-N'-((2-pyridin-2-yl)methyl)oxalamide and = N-benzyl-N'-((2-pyridin-2-yl)methyl)oxalamide), have been synthesized and characterized by X-ray structural analysis, electron paramagnetic resonance (EPR) spectroscopy on single crystals and by SQUID magnetization measurements. X-ray diffraction studies show one-dimensional hydrogen bonded networks of dimeric copper(ii)-complexes bridged by two halide ions and with the two metal centers 3.44-3.

Interplay between the structural and magnetic probes in the elucidation of the structure of a novel 2D layered [V4O4(OH)2(O2CC6H4CO2)4]·DMF.

The title compound has been synthesized under solvothermal conditions by reacting vanadium(V) oxytriisopropoxide with terephthalic acid in N,N-dimethylformamide. A combination of synchrotron powder diffraction, infrared spectroscopy, scanning and transmission electron microscopy, and thermal and chemical analysis elucidated the chemical, structural and microstructural features of a new 2D layered inorganic-organic framework. Due to the low-crystallinity of the final material, its crystal structure has been solved from synchrotron X-ray powder diffraction data using a direct space global optimization technique and subsequent constraint Rietveld refinement.

Single crystals of DPPH grown from diethyl ether and carbon disulfide solutions - crystal structures, IR, EPR and magnetization studies.

Single crystals of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) obtained from diethyl ether (ether) and carbon disulfide (CS₂) were characterized by the X-ray diffraction, IR, EPR and SQUID magnetization techniques. The X-ray structural analysis and IR spectra showed that the DPPH form crystallized from ether (DPPH1) is solvent free, whereas that one obtained from CS₂ (DPPH2) is a solvate of the composition 4DPPH·CS₂. Principal values of the g-tensor were estimated by the X-band EPR spectroscopy at room and low (10 K) temperatures.