Magnetic Susceptibility Measurements Research Articles

Oxovanadium (IV) Complexes of α-Amino Acid Schiff Bases and 2,2'-Bipyridine Ligands: Synthesis, Characterization and Investigation of their Biological Potency

Five new oxovanadium(IV) complexes of the type [VO(L)(bpy)], [where L= 3-hydroxybenzaldehyde-α-alanine (hb-ala), 3-hydroxybenzaldehyde-DL-phenylalanine (hb-pheala), 3-hydroxybenzaldehyde-leucine (hb-leu), 3-hydroxybenzaldehyde-glycine (hb-gly) and 3-hydroxybenzaldehyde-DL-methionine (hb-met) and bpy = 2,2´-bipyridine] have been synthesized and characterized by some physicochemical properties, molar conductance, magnetic susceptibilities measurements, elemental analysis, UV-Visible and FTIR and ESI-MS spectral studies. The molar conductance values showed that the complexes are non-electrolytic in nature. The magnetic moment values of the complexes are in accordance with the d1 electronic configuration of the VIVO2+ moiety and indicates the paramagnetic nature of the complexes. IR spectral data indicates the coordination of tridentate amino acid Schiff base ligands to the vanadyl (VO2+) ion through O, N, O-donor. ESI-MS spectral studies supports the proposed structure of the complexes. The magnetic moment value coupled with electronic spectral data suggested the distorted octahedral geometry of the complexes. All the complexes were screened for their antibacterial activity against three human pathogenic bacteria- Escherichia coli, Staphylococcus aureus and Bacillus cereus with Kanamycin (K-30) standard. The result shows that all the complexes possess to have moderate to strong potential antibacterial activity against all the tested pathogens.

Worldwide Examination of Magnetic Responses to Heavy Metal Pollution in Agricultural Soils

Over the last decade, a large number of studies have been conducted on heavy metals and magnetic susceptibility (χlf) measurement in soils. Yet, a global understanding of soil contamination and magnetic responses remains elusive due to the limited scope or sampling sites of these studies. Hence, we attempted to explore a pollution proxy on a global scale. Through a meta-analysis of data from 102 published studies, our research aimed to provide a worldwide overview of heavy metal pollution and magnetic responses in agriculture soils. We mapped the geographic distribution of nine heavy metals (Cr, Cu, Zn, Pb, Ni, As, Cd, Mn, and Fe) in agricultural soils and explored their pollution sources and contributions. Since 2011, The accumulation of heavy metals has escalated, with industrial activities (31.5%) being the largest contributor, followed by agricultural inputs (27.1%), atmospheric deposition (22.66%), and natural sources (18.74%). The study reports χlf ranging from 6.45 × 10−8 m3/kg to 319.23 × 10−8 m3/kg and χfd from 0.59% and 12.85%, with the majority of the samples being below 6%, indicating heavy metal influence mainly from human activities. Pearson’s correlation and redundancy analysis show significant positive correlations of Pb, Zn, and Cu with χlf (r = 0.51–0.53) and Mn and Fe with χfd (r = 0.50–0.53), while Pb, Zn, Cu, and As metals were shown to be key factors of variation in magnetic response. The average heavy metal pollution load index of 2.03 suggests moderate global agricultural soil pollution, with higher heavy metal contamination in areas of high χlf. Regression analysis confirms soil is considered to be non-polluted below χlf of 26×10−8 m3/kg and polluted above this threshold, with all contamination factors of metals showing a linear correlation with χlf (R = 0.72), indicating that a significant relationship between χlf and the geochemical properties of soils continues to exist on a global scale. This study provides new insights for large-scale agricultural soil quality assessment and magnetic response.

β-Phase Yb5Sb3Hx: Magnetic and Thermoelectric Properties Traversing from an Electride to a Semiconductor.

An electride is a compound that contains a localized electron in an empty crystallographic site. This class of materials has a wide range of applications, including superconductivity, batteries, photonics, and catalysis. Both polymorphs of Yb5Sb3 (the orthorhombic Ca5Sb3F structure type (β phase) and hexagonal Mn5Si3 structure type (α phase)) are known to be electrides with electrons localized in 0D tetrahedral cavities and 1D octahedral chains, respectively. In the case of the orthorhombic β phase, an interstitial H can occupy the 0D tetrahedral cavity, accepting the anionic electron that would otherwise occupy the site, providing the formula of Yb5Sb3Hx. DFT computations show that the hexagonal structure is energetically favored without hydrogen and that the orthorhombic structure is more stable with hydrogen. Polycrystalline samples of orthorhombic β phase Yb5Sb3Hx (x = 0.25, 0.50, 0.75, 1.0) were synthesized, and both PXRD lattice parameters and 1H MAS NMR were used to characterize H composition. Magnetic and electronic transport properties were measured to characterize the transition from the electride (semimetal) to the semiconductor. Magnetic susceptibility measurements indicate a magnetic moment that can be interpreted as resulting from either the localized antiferromagnetically coupled electride or the presence of a small amount of Yb3+. At lower H content (x = 0.25, 0.50), a low charge carrier mobility consistent with localized electride states is observed. In contrast, at higher H content (x = 0.75, 1.0), a high charge carrier mobility is consistent with free electrons in a semiconductor. All compositions show low thermal conductivity, suggesting a potentially promising thermoelectric material if charge carrier concentration can be fine-tuned. This work provides an understanding of the structure and electronic properties of the electride and semiconductor, Yb5Sb3Hx, and opens the door to the interstitial design of electrides to tune thermoelectric properties.

Unusual Stabilisation of Remarkably Bent Tetra-Cationic Tetra-radical Intermolecular Fe(III) μ-Oxo Tetranuclear Complexes.

A hitherto unknown series of air stable, π-conjugated, remarkably bent tetra-cation tetra-radical intermolecular Fe(III) μ-oxo tetranuclear complex, isolated from the dication diradical diiron(III) porphyrin dimers, has been synthesised and spectroscopically characterised along with single crystal X-ray structure determination of two such molecules. These species facilitate long-range charge/radical delocalisation through the bridge across the entire tetranuclear unit manifesting an unusually intense NIR band. Assorted spin states of Fe(III) centres are stabilised within these unique tetranuclear frameworks: terminal six-coordinate iron centres stabilise the admixed intermediate spin states while the central five-coordinate iron centres stabilise the high-spin states. Variable temperature magnetic susceptibility measurements indicated strong antiferromagnetic coupling for the Fe(III)-O-Fe(III) unit while the exchange interactions between the Fe centres and the porphyrin π-cation radicals are weaker as supported both by magnetic data and DFT calculations. The nature of orbital overlap between the SOMOs of Fe(III) and π* orbital of the porphyrin was found to rationalise the observed exchange coupling, establishing such a complex magnetic exchange in this tetranuclear model with a significant bioinorganic relevance.

Unusual Stabilisation of Remarkably Bent Tetra‐Cationic Tetra‐radical Intermolecular Fe(III) μ‐Oxo Tetranuclear Complexes

AbstractA hitherto unknown series of air stable, π‐conjugated, remarkably bent tetra‐cation tetra‐radical intermolecular Fe(III) μ‐oxo tetranuclear complex, isolated from the dication diradical diiron(III) porphyrin dimers, has been synthesised and spectroscopically characterised along with single crystal X‐ray structure determination of two such molecules. These species facilitate long‐range charge/radical delocalisation through the bridge across the entire tetranuclear unit manifesting an unusually intense NIR band. Assorted spin states of Fe(III) centres are stabilised within these unique tetranuclear frameworks: terminal six‐coordinate iron centres stabilise the admixed intermediate spin states while the central five‐coordinate iron centres stabilise the high‐spin states. Variable temperature magnetic susceptibility measurements indicated strong antiferromagnetic coupling for the Fe(III)−O−Fe(III) unit while the exchange interactions between the Fe centres and the porphyrin π‐cation radicals are weaker as supported both by magnetic data and DFT calculations. The nature of orbital overlap between the SOMOs of Fe(III) and π* orbital of the porphyrin was found to rationalise the observed exchange coupling, establishing such a complex magnetic exchange in this tetranuclear model with a significant bioinorganic relevance.

Synthesis, crystal structure, and thermodynamic properties of two new selenate chlorides: M2Cu(SeO4)Cl2 with M = K and Rb

Two new selenate chlorides have been prepared for the first time by hydrothermal method. Their crystal structures have been determined. Both compounds are related to the chlorothionite mineral structure type but not isostructural to each other. K2Cu(SeO4)Cl2 crystallize in the orthorhombic system with the space group Pnma (#62) and unit cell parameters a = 7.7941(2)Å, b = 6.1297(2) Å, c = 16.6644(5) Å, V = 796.15(4) Å3, Z = 4 whereas Rb2Cu(SeO4)Cl2 crystallize in monoclinic system, P21/n (#14), and parameters a = 8.0701(3), b = 12.9474(5), c = 16.9354(7), β = 103.657(2)°, V = 1719.49(12) Å3, Z = 8. Potassium compound are isostructural to the related sulfate chloride, while rubidium selenate is differ from their sulfate analogue and from prototype compound K2Cu(SO4)Cl2. Both examined crystal structures feature copper ions in planar coordination CuO2Cl2 which form isolated magnetic chains along ⟨0 1 0⟩ direction in the structure. The study of M2Cu(SeO4)Cl2 was carried out in measurements of magnetic susceptibility χ(T) = M/B in the temperature range 2–350 K, magnetization M(B) at 2 K and specific heat Cp(T) in the range 2–120 K. At lowering temperature, the magnetic susceptibility exhibits no anomalies and follows by Curie law. An increase of the Cp(T) curve below 3 ÷ 8 K indicates the release of magnetic entropy. The study of thermodynamic properties unexpectedly shows that the investigated selenates M2Cu(SeO4)Cl2 (M = K and Rb) behave like paramagnets and the interaction between copper ions in the structural chains is negligible, opposite related sulfates demonstrating 1D magnetic behavior for Cu2+ magnetic ions.

Magnetic short-range order and Griffiths-like phase in the S-1/2 spin-dimer ferromagnet BaCu(SeO3)2

The polycrystals of S = 1/2 spin-dimer compound BaCu(SeO3)2 have been synthesized by using solid-state reaction. Without long-range order, the magnetic susceptibility χ(T) curve presents two anomalies at T1 = 5 K and TG = 58 K due to antiferromagnetic (AFM) short-range order and short-range ferromagnetic (FM) correlations, respectively, which is further supported by the specific heat and electron spin resonance data. The high-temperature χ(T) curve follows the Curie-Weiss law with θCW = 11.3 K, showing the dominant intradimer FM interaction. The magnetization M(H) curve at 2 K is characteristic of an AFM-FM transition at 0.4 T, suggesting the weak interdimer AFM couplings. The density function theory calculations and quantum Monte Carlo simulations allow an estimation of the intradimer and interdimer exchanges with J1/kB = 39.09 K, J2/kB = −1.51 K, and J3/kB = −1.68 K. Interestingly, the χ−1(T) curve within θCW <T <TG deviates downward from paramagnetic Curie-Weiss behavior, mimicking the Griffiths-like phase. This is further supported by the ac magnetic susceptibility and magnetic relaxation measurements. The competing intradimer FM and interdimer AFM exchanges with a subtle ratio between them are proposed to be responsible for the formation of Griffiths-like phase.

Signature of possible spin liquid state at 2K in spin-frustrated Cr1-xFexPSe3 alloy

Disordered spin systems typically exhibit glass-like characteristics below the glass transition temperature [1–4]. However, when the competition between ferromagnetic and antiferromagnetic couplings is balanced, the spin liquid state persists towards zero Kelvin rather than a glass state [5]. This unique state is known as the quantum spin liquid state. In this study, we examined a potential spin liquid state in the two-dimensional spin-frustrated Cr1-xFexPSe3 alloy by magnetic susceptibility measurements as a function of temperature and doping. Two end compounds, CrPSe3 and FePSe3, exhibit an antiferromagnetic order. With the Fe doping, the antiferromagnetic order of frustrated CrPSe3 gradually weakened and reached its minimum transition temperature at the critical concentration of x = 0.33. This weak order became indeterminate when a high magnetic field was applied, indicating the possibility of converting the magnetic order to the spin liquid state down to 2 K. With further doping, an antiferromagnetic order was observed in the Fe-dominated compound. Our results provide a new two-dimensional flat form for exploring quantum spin liquid states.

Copper(II) complexes of 1,3-dimethyl-(5-(8′-quinolinylazo)-6-aminouracil: Structures, magnetism and biological activity

Two Cu(II)-complexes were synthesized using 1,3-dimethyl-5-(8′-quinolinylazo)-6-aminouracil (H2L) ligand in combination with thiocyanide (SCN−) and azide (N3−) pseudohalides as co-ligands. The thiocyanide (SCN−) co-ligand guided to form monomeric aquo-isothiocyanato-Cu(II) complex, [CuII(HL)(NCS)(H2O)] (1) of H2L. Under similar reaction condition, the azide (N3−) co-ligand led to form polymeric azido-Cu(II) complex, [CuII(L′)(N3)]n, (2) of HL′, where HL′ was an in-situ generated new ligand, 1,3-dimethyl-(5-(8′-quinolinylazo)-6-hydroxouracil (HL′) from H2L. Both are tridentate ligands with different uracil-donor sites (H2L: NqNaNu, HL′: NqNaOu). The complexes are monoclinic with space groups C2/c (Z = 8) and P21/n (Z = 4) for 1 and 2, respectively. They possess slightly distorted square-pyramidal coordination around CuII ions with elongation at the axial sites (Cu1-O3 (water) bond is 2.2698(13)Å for 1 and Cu1-Oμ-uracil bond is 2.5525(13)Å for 2). The polymeric nature of 2 is availed through one of the exocyclic-C = O groups of HL′, making Cu…Cu spacing to 7.9973(3)Å. Direct current (dc) variable-temperature magnetic susceptibility measurements on polycrystalline samples of 1 and 2 were carried out in the temperature range 1.8-300 K. The 1 is devoid of any significant interaction between the mononuclear units. Magnetic properties show weak ferromagnetic exchange coupling within the chain (J = 0.61 cm−1) in 2. The TD-DFT study reveals that ILCT, LMCT and d-d types of electronic transitions are involved in both the complexes. The evaluated biological efficacy of the compounds against plant pathogens it is revealed that the complex 1 has an antibacterial and complex 2 has antifungal properties.

Alkoxy-Bridged Dicopper(II) Cores Meet Tetracyanonickelate Linkers: Structural, Magnetic, and Theoretical Investigation of Cu/Ni Coordination Polymers.

Two heterometallic Cu(II)/Ni(II) coordination polymers, [Cu2(Hbdea)2Ni(CN)4]n (1) and [Cu2(dmea)2Ni(CN)4]n·nH2O (2), were successfully self-assembled in water by reacting Cu(II) nitrate with H2bdea (N-butyldiethanolamine) and Hdmea (N,N-dimethylethanolamine) in the presence of sodium hydroxide and [Ni(CN)4]2-. These new coordination polymers were investigated by single-crystal and powder X-ray diffraction and fully characterized by FT-IR spectroscopy, thermogravimetry, elemental analysis, variable-temperature magnetic susceptibility measurements, and theoretical DFT and CASSCF calculations. Despite differences in crystal systems, in both compounds, each dinuclear building block [Cu2(μ-aminopolyalcoholate)2]2+ is bridged by diamagnetic [Ni(CN)4]2- linkers, resulting in 1D (1) or 2D (2) metal-organic architectures. Experimental magnetic studies show that both compounds display strong antiferromagnetic coupling (J = -602.1 cm-1 for 1 and -151 cm-1 for 2) between Cu(II) ions within the dimers mediated by the μ-O-alkoxo bridges. These results are corroborated by the broken symmetry DFT studies, which also provide further insight into the electronic structures of copper dimeric units. By reporting a facile self-assembly synthetic protocol, this study can be a model to widen a still limited family of heterometallic Cu/Ni coordination polymer materials with different functional properties.

Metal saccharinate complexes with N,N-bis(2-hydroxyethyl)ethylendiamine: Synthesis, structural, thermal decomposition and DFT studies

New Co(III), Ni(II), Cu(II), and Zn(II) saccharinate (Sac) complexes bearing with N,N-bis(2-hydroxyethyl)ethylenediamine (N-bishydeten), namely [Co(2HN-bishydeten)2](Sac)⋅2H2O, [Ni(Sac)2(N-bishydeten)], [Cu(N-bishydeten)2](Sac)2 and [Zn(Sac)2(N-bishydeten)] were synthesized and characterized using UV–Vis, IR spectroscopy and magnetic susceptibility measurements. The crystal structures of the complexes were analysed by single crystal X-ray diffraction. Both N-bishydeten and Sac displayed coordination versality. The N-bishydeten ligands were octahedrally coordinated as two tridentate anionic ligands (2HN-bishydeten) (N, N, O-) to the Co(III) and two tridentate neutral ligands (N, N, O) to the Cu(II). The anionic Sac ligand was also located outside the coordination sphere in these complexes. However, the N-bishydeten ligand behaved as a tetradentate ligand (O, N, O, N) in the Ni(II) and Zn(II) complexes while two Sac ligands were coordinated the corresponding metals ions in a monodentate fashion, one through the N atom and the other via the carbonyl O atom. Thermal decomposition of the complexes was studied in inert atmosphere and thermal analysis data (TG and DTA) indicated multi-step decompositions of the metal complexes decomposed in a single stage. The thermal decomposition products were estimated as metal oxides. Finally, the structural properties of all complexes were investigated through quantum chemical computations.

Synthesis and Characterization of Biopotent Transition Metal Complexes of Schiff Base 2-{(1)-1-[2-(1,3-Benzothiazol-2-yl)hydrazinylidene]ethyl}-6,10b-dihydro-3H-benzo[f]chromen-3-one and their Biological Evaluation

Three transition metal(II) complexes (M = Co/ Zn/Pd) were synthesized by using a newly synthesized Schiff base ligand 2-{(1E)-1-[2-(1,3-benzothiazol-2-yl)hydrazinylidene]ethyl}-6,10b-dihydro-3H-benzo[f]chromen-3-one (L) by conventional method. The structure of the compounds were determined by physical and analytical techniques like UV-visible, FT-IR, 1H and 13C NMR and mass spectroscopic techniques and the crystallinity and inter-planar distance of the complexes were confirmed by XRD. The electron density in HOMO and LUMO was determined by DFT studies. The studies of electronic spectra and measurements of magnetic susceptibility suggest that Co(II) complex shows an octahedral geometry, Pd(II) complexes show square planar geometry and (ZnL2Cl2) complex shows tetrahedral geometry. The molar conductivity results suggested the non-electrolytic nature of the metal(II) complexes. The synthesized compounds was tested against antibacterial activity for Gram-positive and Gram-negative bacteria. The molecular docking study demonstrated that the ligand and its metal(II) complexes possess antibacterial and anticancer properties, and the results showed that the compounds were effective against the microorganisms that were examined. Furthermore, the results found that metal(II) complexes provided enhanced immunity against cancer cell lines.

Realization of Organocerium-Based Fullerene Molecular Materials Showing Mott Insulator-Type Behavior.

Electron-rich organocerium complexes (C5Me4H)3Ce and [(C5Me5)2Ce(ortho-oxa)], with redox potentials E1/2 = -0.82 V and E1/2 = -0.86 V versus Fc/Fc+, respectively, were reacted with fullerene (C60) in different stoichiometries to obtain molecular materials. Structurally characterized cocrystals: [(C5Me4H)3Ce]2·C60 (1) and [(C5Me5)2Ce(ortho-oxa)]3·C60 (2) of C60 with cerium-based, molecular rare earth precursors are reported for the first time. The extent of charge transfer in 1 and 2 was evaluated using a series of physical measurements: FT-IR, Raman, solid-state UV-vis-NIR spectroscopy, X-ray absorption near-edge structure (XANES) spectroscopy, and magnetic susceptibility measurements. The physical measurements indicate that 1 and 2 comprise the cerium(III) oxidation state, with formally neutral C60 as a cocrystal in both cases. Pressure-dependent periodic density functional theory calculations were performed to study the electronic structure of 1. Inclusion of a Hubbard-U parameter removes Ce f states from the Fermi level, opens up a band gap, and stabilizes FM/AFM magnetic solutions that are isoenergetic because of the large distances between the Ce(III) cations. The electronic structure of this strongly correlated Mott insulator-type system is reminiscent of the well-studied Ce2O3.

Syntheses, crystal structures, and magnetic behaviors of phenoxo-bridged manganese compounds based on tetradentate Schiff bases

Six Mn(II)/Mn(III) coordination compounds with tetradentate Schiff bases, [Mn(L1)(N3)]2 (1), [Mn(L2)(N3)]2 (2), [Mn(L1)(SCN)]2 (3), [Mn(L2)(SCN)]2[Mn(L2)(SCN)(C2H5OH)]2 (4), [Mn(L1)(CH3OH)]2 (5), and [Mn3(L2)2(CH3COO)2] (6) [H2L1 = N,N'-bis(5-chloro-salicylaidimine)-1,2-diaminop-ropane), H2L2 = N,N'-bis(5-chloro-salicylaidimine)-2,2-dimethylpropane-1,3-diami- ne], were structurally and magnetically characterized by X-ray single crystal diffraction, powder X-ray diffraction (PXRD), elemental analysis, infrared (IR) spectroscopy and magnetic susceptibility measurement. Structural analysis reveals that each manganese center displays a typical Jahn-Teller distortion. Compounds 1, 2, 3 and 5 are binuclear systems in which two central manganese atoms are connected by di-u2-phenoxo-bridging from two inverse tetradentate ligands. The asymmetric unit of compound 4 contains two moieties, which is composed of a dimeric unit [Mn(L1)(SCN)]2 and two monomeric units [Mn(L1)(SCN)(C2H5OH)]. Compound 6 is a linear homo-trinuclear structure. Dc variable-temperature magnetic susceptibility measurements show that compounds 1, 2, 4 and 5 exhibit paramagnetic behaviors with J = +0.202 cm−1 for 1, J = +0.203 cm−1 for 2, J = +1.03 cm−1 for 4 and + 0.152 cm−1 for 5, respectively, whereas compounds 3 and 6 show a strong antiferromagnetic interaction between the high-spin metal centers. In addition, we investigated the relationship between the structures and magnetic behaviour.

Superconductivity and Charge-Density-Wave-Like Transition in Th2Cu4As5.

We report the synthesis, crystal structure, and physical properties of a novel ternary compound, Th2Cu4As5. The material crystallizes in a tetragonal structure with lattice parameters a = 4.0639(3) Å and c = 24.8221(17) Å. Its structure can be described as an alternating stacking of fluorite-type Th2As2 layers with antifluorite-type double-layered Cu4As3 slabs. The measurement of electrical resistivity, magnetic susceptibility, and specific heat reveals that Th2Cu4As5 undergoes bulk superconducting transition at 4.2 K. Additionally, all these physical quantities exhibit anomalies at 48 K, accompanied by a sign change in the Hall coefficient, suggesting a charge-density-wave-like (CDW) phase transition. Drawing from both experimental data and band calculations, we propose that the superconducting and CDW-like phase transitions are, respectively, associated with the Cu4As3 slabs and the As plane in the Th2As2 layers.

Synthesis and characterization of novel Ru(III) complexes of 2‐aminopyrazine: Interaction with biomolecules, antineoplastic activity, and computational investigation

Ruthenium (III) complexes (1–3) of 2‐aminopyrazine (pyz) with general formula of [Hpyz][RuCl4(DMSO)(pyz)](1), Na[RuCl4(pyz)(DMSO)] (2), and (Hpyz)[RuCl4(pyz)2].2H2O (3) have been synthesized and characterized by elemental analyses, FTIR, 1H NMR, and UV–visible spectroscopy, along with the magnetic susceptibility and cyclic voltammetry measurements. The molecular structures of the complexes have also been optimized using density functional theory (DFT) calculation which demonstrates an octahedral geometry to be adopted by the Ru(III) ion. The UV–visible and fluorescence spectra were employed to study the interaction of the compounds with nucleic acid (ctDNA and tRNA) and bovine serum albumin (BSA). The data showed a higher tendency for the ligand and its complexes (1–3) to interact with biomolecules (1 &gt; 2 &gt; 3). All complexes showed potent in vitro anticancer activity against three human cancer cell lines and high safety against normal cell lines as complex (1) is the most active one, it was selected for the flow cytometric evaluation for cell death mode, cell cycle analysis, and matrix metalloproteinase‐9 (MMP9) expression in treated MDA‐231 cells. Proliferating cell nuclear antigen (PCNA) expression and VEGF concentration were evaluated in the treated cells and compared with the untreated ones. Our study proved that complex (1) arrests the cell cycle, inhibits DNA transcription, reduces both MMP9 (validated by our molecular docking investigation targeting MMP9 protein) and PCNA expressions, and induces apoptotic cell death, leading to cancer metastasis prevention.

Growth and magnetocaloric effect of Na2Gd2(BO3)2O crystal

High-quality Na2Gd2(BO3)2O crystals have been successfully grown using the top-seeded solution growth method (TSSG), employing a Na2O - NaF - B2O3 flux system with optimal molar ratios of Na2Gd2(BO3)2O : Na2CO3 : NaF : H3BO3 = 1:2:6:4. The magnetic and magnetocaloric properties were investigated including magnetic susceptibility (χ), magnetization (M), and isothermal magnetic entropy change (−ΔSm) measurements. Na2Gd2(BO3)2O exhibits a large magnetocaloric effect with a maximum − ΔSm of 41.6 J·kg−1·K−1 at 2 K and 7 T, which is higher than that of commercial Gd3Ga5O12 (GGG, −ΔSm = 38.4 J·kg−1·K−1 at 2 K and 7 T) and most other Gd3+-based borates, showing the potential application in the field of magnetic refrigeration.

Cooperative effects of ligands and Counteranions in mononuclear Manganese(III) Schiff-base spin crossover complexes

The flexible hexadentate Schiff-base ligands (R-sal-N-1,5,8,12)2− can be easily obtained by modifying the different substituents at the 5 or 3,5 positions on the phenyl rings of the salicylaldehyde. We report in this paper the syntheses, crystal structures and magnetic properties of three new mononuclear manganese(III) complexes [Mn(R-sal-N-1,5,8,12)]Y (R = 5-H, Y = BF4 (1); R = 3,5-diCl, Y = SbF6 (2); R = 5-tBu, Y = ClO4 (3)). All the complexes have an analogous monocationic MnN4O2 surrounding offered by the flexible hexadentate ligand in a distorted octahedral geometry. Magnetic susceptibility measurements demonstrated that complex 1 maintains a high-spin (HS) state between 2 and 400 K due to the closing packing, while complex 2 shows a cooperative and complete one-step thermo-induced spin state switching with T1/2 of 194 K. As for complex 3, single-crystral X-ray structural studies show the existence of a large amount of HS manganese(III) ions at 100 K and it exhibits a surprisingly gradual SCO process with a hysteresis width of 6 K at lower temperature.

Magnetism, heat capacity, magnetocaloric effect, and magneto-transport properties of heavy fermion antiferromagnet CeGaSi

We synthesize high-quality single crystal of CeGaSi by a Ga self-flux method and investigate its physical properties through magnetic susceptibility, specific heat and electrical resistivity measurements as well as high pressure effect. Magnetic measurements reveal that an antiferromagnetic order develops below T m ∼ 10.4 K with magnetic moments orientated in the ab plane. The enhanced electronic specific heat coefficient and the negative logarithmic slope in the resistivity of CeGaSi indicate that the title compound belongs to the family of Kondo system with heavy fermion ground states. The max magnetic entropy change −ΔSMmax (μ 0 H⊥c, μ 0 H = 7 T) around T m is found to reach up to 11.85 J⋅kg−1⋅K−1. Remarkably, both the antiferromagnetic transition temperature and −lnT behavior increase monotonically with pressure applied to 20 kbar (1 bar = 105 Pa), indicating that much higher pressure will be needed to reach its quantum critical point.

Oxovanadium (IV) Complexes of α-Amino Acid Schiff Bases and Polypyridyl Ligands: Synthesis, Characterization and Antimicrobial Activity

Oxovanadium(IV) complexes of the type [VO(L)(bpy)] (V-1 to V-5) have been synthesized and characterized by FTIR and UV-Vis spectra, molar conductance, melting points, and magnetic susceptibilities measurements, where L= N-salicylidene-β-alanine (sal-ala), N-salicylidene-glycine (sal-gly), N-salicylidene-DL-β-phenylalanine (sal-pheala), N-salicylidene-leucine (sal-leu), and N-salicylidene-DL-methionine (sal-met), and bpy is 2,2´-bipyridine. The infrared spectral data reveals that the tridentate nature of the amino acid-based Schiff base ligand and the coordination of the ligand through azomethine nitrogen, phenolic oxygen and carboxylate oxygen with vanadyl (VO2+) ion. All of these complexes were determined to be non-electrolyte in nature, according to conductivity measurements. The magnetic moment measurements have been attributed that these complexes are paramagnetic and have d1 configuration of vanadium (IV) ion. In Virto antimicrobial activity of the synthesized complexes was evaluated against two gram-positive (Bacillus subtilis and Staphylococcus aureus) and two gram-negative (Escherichia coli, Proteus vulgaris) bacterial strains.