Magnetic Susceptibility Measurements Research Articles

Novel α-N-heterocyclic thiosemicarbazone complexes: synthesis, characterization, and antimicrobial of properties investigation.

In this paper, eight novel α-N-heterocyclic thiosemicarbazone complexes were synthesized in search of new biologically active compounds, and characterized via organic elemental analysis, nuclear magnetic resonance spectroscopy, infrared spectra, thermogravimetric analysis, ultraviolet-visible spectroscopy, molar conductance and magnetic susceptibility measurements. The in vitro antimicrobial activity of these complexes was examined against ten disease-causing pathogens: Gram-positive bacteria (Micrococcus luteus ATCC9341, Staphylococcus epidermidis ATCC12228, Bacillus cereus RSKK863) and Gram-negative bacteria (Pseudomonas aeroginosa ATCC27853, Klebsiella pneumonia ATCC27853, Enterobacter aerogenes ATCC51342, Salmonella typhi H NCTC9018394, Shigella dysenteria NCTC2966, Proteus vulgaris RSKK96026) and yeast (Candida albicans Y-1200-NIH). The results revealed that the α-N-heterocyclic thiosemicarbazone compounds showed potent activity. It was observed that all thiosemicarbazone complexes were more susceptible to Gram-negative strains based on the presence of an electron-withdrawing substituent (-Br/-Cl/-F). It was determined that thiosemicarbazone Cu2+complexes showed stronger antifungal effects.

Self-Assembled Lanthanide Phosphinate Square Grids (Ln = Er, Dy, and Tb): Dy4 Shows SMM/SMT and Tb4 SMT Behavior.

Tetranuclear [2 × 2] square-grid-like LnIII clusters have been synthesized by reacting LnCl3·6H2O salts with bis[α-hydroxy(p-bromophenyl)methyl]phosphinic acid [R2PO2H, where R = CH(OH)PhBr] and pivalic acid. Single-crystal X-ray diffraction studies show the formation of [Me4N]2[Ln4(μ2-η1:η1-PO2R2)8(η2-CO2But)4(μ4-CO3)] [Ln = Er (1), Dy (2), and Tb (3)]. Direct-current studies reveal significant ferromagnetic interactions between DyIII in 2 and TbIII in 3 and an antiferromagnetic interaction between ErIII in 1. Dynamic magnetic susceptibility measurements confirm a single-molecule magnet (SMM) behavior in both 0 and 1200 Oe applied magnetic fields for 2. Complexes 2 and 3 show single molecular toroic (SMT) behavior with a mixed magnetic moment.

Mineral composition of lake Sabakty sediments as an indicator of paleoclimate, Southern Urals, Russia

Relevance. Reconstruction of climatic changes based on the lacustrine sediments of lakes makes it possible to identify climatic trends and events in the late Quaternary. The Urals is considered as one of the climatic divisions, therefore, studies of the conditions of lake sedimentation, including climatic ones, are relevant in this area. Aim. To study mineral composition as an indicator of paleoclimate of Lake Sabakty sediments. Object. Core of Lake Sabakty sediments (length is 298 cm). The age of the core is ~25 thousand years old. Materials and methods. Sampling was carried out taking into account seismoacoustic data, lithological description, as well as measurements of magnetic susceptibility and radiometric dating data. The granulometric analysis was carried out by laser granulometry using a Bluewave particle size analyzer (Microtrac, USA) combined with a sample loading and circulation system with an integrated ultrasonic dispersant. Mineral composition of the sediments was determined using the D2 PHASER X-ray diffractometer and the Merlin auto-emission scanning electron microscope. Results. The predominance of the siltstone fraction was established. The mineral composition is characterized by the predominance of allotigenic minerals in sediments (quartz, microcline, albite, mica, chlorite, mixed-layer clay minerals, hornblende, kaolinite) according to X-ray diffraction and electron microscopy. Autigenic minerals include biogenic silica (cristobalite, tridymite), pyrite, carbonates (calcite, dolomite), sulfates (gypsum, barite). Conclusions. The ratio of allogenic and autogenic components reflects the changes in the accommodation of the reservoir and the supply of clastic material associated with changes in climate humidity. Changes in climate humidity are reflected in changes in the contents of carbonate and sulfate minerals. At the beginning of sedimentation, Lake Sabakty was shallow and mineralized due to climate aridization, which probably included the global Bond 8 event (~26000–11700 BP). The study of the mineral composition of the sediments of Lake Sabakty allowed us to establish the events of climate aridization: ~10000 BP, ~7600 BP, ~6900 BP ~1900 BP and ~1400 BP. In Sabakty Lake, there is a bright episode of a decrease in climate humidity in the range of ~7300-5200 BP, which is marked by an increase in carbonate content up to 70% and the detection of gypsum at ~6900 BP.

Crystal and thermodynamic properties of [formula omitted], (X = Al, Ga)

The crystal and thermodynamic properties of Tb2Ni2X (X = Al, Ga) are reported through measurements of X-ray diffraction (XRD), magnetic susceptibility, χ(T), magnetization, M(μ0H) and heat capacity, Cp(T). XRD pattern analysis confirms the orthorhombic W2CoB2-type structure with the space group of Immm. χ(T) at high temperature for both compounds follows the Curie – Weiss relationship giving an effective magnetic moment close to that expected for the trivalent Tb ion. The low-temperature χ(Cp) data indicate that both compounds order antiferromagnetically at TN = 41 K (40.4 K) and 41.5 K (41.4 K) for Al and Ga compounds, respectively. Cp(T) data of the nonmagnetic counterparts Y2Ni2X (X = Al, Ga) are well described by the Debye model giving a Debye temperature, θD = 236.9(4) K and 225.3(2) K for Al and Ga compounds, respectively. The low-temperature part of the 4f-magnetic contribution to the total heat capacity, C4f(T) can be described by the antiferromagnetic spin-wave dispersion, giving an energy gap Δsw = 47(3) K and 26(2) K for Al and Ga compounds, respectively. The 4f – magnetic entropy S4f(T) for both compounds reaches the value of 2Rln(2) close to their respective TN values.

Magnetic properties of binary alloys Ni[formula omitted]Mo[formula omitted] and Ni[formula omitted]Cu[formula omitted] close to critical concentrations

The search for the ferromagnetic quantum critical point (FM QCP) has always been a captivating research topic in the scientific community. In pursuit of this goal, we introduced nonmagnetic transition metals to alloy with elemental nickel, and studied the magnetic properties of nickel binary alloys Ni1−xMox and Ni1−yCuy as a function of x and y up to the critical concentrations xcr and ycr at which the FM transition TC disappears. TC−x(y) phase diagrams were constructed via the Arrott–Noakes scaling of magnetization data. An enhanced Sommerfeld coefficient (the value of C/T as T→0) is observed near xcr and ycr, manifesting the effect of quantum fluctuations. However, the spin glass behavior is identified through the ac magnetic susceptibility measurements. This observation rules out the possibility of the existence of the FM QCP in both systems.

Single-Step Synthesis of An Ideal Chain Antiferromagnet [H2(4,4'-bipyridyl)](H3O)2Fe2F10 with Spin S = 5/2.

One-dimensional (1D) magnets are of great interest owing to their intriguing quantum phenomena and potential application in quantum computing. We successfully synthesized an ideal antiferromagnetic spin S = 5/2 chain compound [H2(4,4'-bpy)](H3O)2Fe2F10 (4,4'-bpy = 4,4'-bipyridyl) 1, using a single-step low-temperature hydrothermal method under conditions that favors the protonation of the bulky bidentate ligand 4,4'-bpy. Compound 1 consists of well-separated (Fe3+-F-)¥ chains with a large Fe-F-Fe angle of 174.8°. Both magnetic susceptibility and specific heat measurements show that 1 does not undergo a magnetic long-range ordering down to 0.5 K, despite the strong Fe-F-Fe intrachain spin exchange J with J/kB = -16.2(1) K. This indicates a negligibly weak interchain spin exchange J'. The J'/J value estimated for 1 is extremely small (< 2.8×10-6), smaller than those reported for all other S = 5/2 chain magnets. Our hydrothermal synthesis incorporates both [H2(4,4'-bpy)]2+ and (H3O)+ cations into the crystal lattice with numerous hydrogen bonds, hence effectively separating the (Fe3+-F-)¥ spin chains. This single-step hydrothermal synthesis under conditions favoring the protonation of bulky bidentate ligands offers an effective synthetic strategy to prepare well-separated 1D spin chain systems of magnetic ions with various spin values.

Single‐Step Synthesis of An Ideal Chain Antiferromagnet [H2(4,4′‐bipyridyl)](H3O)2Fe2F10 with Spin S = 5/2

One‐dimensional (1D) magnets are of great interest owing to their intriguing quantum phenomena and potential application in quantum computing. We successfully synthesized an ideal antiferromagnetic spin S = 5/2 chain compound [H2(4,4′‐bpy)](H3O)2Fe2F10 (4,4′‐bpy = 4,4′‐bipyridyl) 1, using a single‐step low‐temperature hydrothermal method under conditions that favors the protonation of the bulky bidentate ligand 4,4′‐bpy. Compound 1 consists of well‐separated (Fe3+−F−)¥ chains with a large Fe−F−Fe angle of 174.8°. Both magnetic susceptibility and specific heat measurements show that 1 does not undergo a magnetic long‐range ordering down to 0.5 K, despite the strong Fe−F−Fe intrachain spin exchange J with J/kB = –16.2(1) K. This indicates a negligibly weak interchain spin exchange J′. The J′/J value estimated for 1 is extremely small (&lt; 2.8×10‐6), smaller than those reported for all other S = 5/2 chain magnets. Our hydrothermal synthesis incorporates both [H2(4,4′‐bpy)]2+ and (H3O)+ cations into the crystal lattice with numerous hydrogen bonds, hence effectively separating the (Fe3+−F−)¥ spin chains. This single‐step hydrothermal synthesis under conditions favoring the protonation of bulky bidentate ligands offers an effective synthetic strategy to prepare well‐separated 1D spin chain systems of magnetic ions with various spin values.

Heterocyclic Schiff Base Complexes of Bivalent Transition Metals: Microwave-Assisted Green Synthesis, Structure Elucidation and Antimicrobial Studies

A heterocyclic Schiff base ligand [LH] namely {5‐[(E)‐[(1H‐pyrrol‐2‐yl)methylidene]amino]‐ 1,3,4‐thiadiazole‐2‐thiol}(NNN donor) and its divalent transition metals (Co2+, Ni2+, Cu2+ and Zn2+) mononuclear complexes were synthesised efficiently in relatively very short times (from one-two hours to 6-15 minutes) with higher yields [from 59% (conventional method) to 90% (green method)] by microwave-assisted greener process is presented here. The ligand and its complexes were characterised by elemental analysis, molar conductance, and magnetic susceptibility measurements and spectroscopic (IR, electronic, and NMR) analyses. All investigated complexes were found to be six coordinated ML2 [1:2 (metal: Ligand) ratio] type which possessed mononuclear octahedral geometry. The ligand and its metal complexes were screened for antimicrobial activity by the disc diffusion method, and the results indicate that the metal complexes are better antimicrobial agents compared to the Schiff base and the metal complexes have followed antimicrobial trends: Cu(II) complex &gt; Co(II) complex &gt; Ni(II) complex &gt; Zn(II) complex &gt; Schiff base

Weyl fermion excitations in the ideal Weyl semimetal CuTlSe2

An ideal Weyl semimetal is characterized by a dispersion in which only Weyl cones intersect the Fermi level, with low-energy behavior being governed by Weyl fermions. Although ideal Weyl semimetals have long been anticipated, only a few are realized in nonmagnetic materials. In this study, we confirm the presence of Weyl-fermion excitations in the ideal Weyl semimetal CuTlSe2 via a combination of magnetoresistance, Hall-effect, magnetic-susceptibility, nuclear magnetic resonance (NMR), and muon-spin relaxation (µSR) experiments. Magnetoresistance measurements reveal a negative longitudinal magnetoresistance (LMR), which scales as B2, while Hall-effect results indicate a predominant contribution from Weyl fermions with a hole-type charge. Magnetic susceptibility and µSR measurements indicate the lack of any intrinsic spontaneous magnetic moments down to base temperature. Finally, the NMR results can be modeled by a two-component effective Hamiltonian, which reproduces well the temperature-dependent Cu63 NMR (T1T)−1 factor, shown to scale as T2 below 100 K and as T1 above 100 K. Overall, we find that the extremely low concentration (1017cm−3) of carriers in CuTlSe2 originates from an ideal nonmagnetic Weyl semimetallic state, persisting up to a thermal excitation energy of 9 meV (100 K), above which trivial electronic bands close to EF take over. Our findings highlight CuTlSe2 as a new member of the intriguing class of Weyl semimetals. Published by the American Physical Society 2024

Stabilization of Short‐ and Long‐Range Magnetic Ordering through the Cooperative Effect of 1D [CuO4]∞ Chains and [CuO2X2] Quadrilateral in Quasi‐1D Spin‐1/2 Systems

AbstractQuasi‐1D chain antiferromagnets with reduced structural dimensionality are a rich playground for investigating novel quantum phenomena. We report the synthesis, crystal structure, and magnetism of two novel quasi‐1D antiferromagnets, β‐PbCu2(TeO3)2Cl2 (I) and PbCu2(TeO3)2Br2 (II). Their magnetic frameworks are constructed via Cu‐based quasi‐1D [Cu(2)O4]∞ zigzag chains with square‐planar [Cu(1)O2X2] (X=Cl or Br) separated among 1D chains. Specific heat measurements show λ peaks at ~9 K and ~19 K for I and II, respectively. Moreover, both broad maximums (χmax=90 K for I and 80 K for II) and small kinks (TN≈9 K for I and 19 K for II) have been observed in magnetic susceptibility measurements of I and II. Bonner–Fisher model fitting, and theoretical analyses were performed to evaluate the magnetic exchange interactions. Our experimental and theoretical results and structure‐properties relationship analysis reveal the coexistence of short‐ and long‐range magnetic ordering from the cooperative effect of 1D [CuO4]∞ chains and [CuO2X2] quadrilateral.

Stabilization of Short- and Long-Range Magnetic Ordering through the Cooperative Effect of 1D [CuO4]∞ Chains and [CuO2X2] Quadrilateral in Quasi-1D Spin-1/2 Systems.

Quasi-1D chain antiferromagnets with reduced structural dimensionality are a rich playground for investigating novel quantum phenomena. We report the synthesis, crystal structure, and magnetism of two novel quasi-1D antiferromagnets, β-PbCu2(TeO3)2Cl2 (I) and PbCu2(TeO3)2Br2 (II). Their magnetic frameworks are constructed via Cu-based quasi-1D [Cu(2)O4]∞ zigzag chains with square-planar [Cu(1)O2X2] (X=Cl or Br) separated among 1D chains. Specific heat measurements show λ peaks at ~9 K and ~19 K for I and II, respectively. Moreover, both broad maximums (χmax=90 K for I and 80 K for II) and small kinks (TN≈9 K for I and 19 K for II) have been observed in magnetic susceptibility measurements of I and II. Bonner-Fisher model fitting, and theoretical analyses were performed to evaluate the magnetic exchange interactions. Our experimental and theoretical results and structure-properties relationship analysis reveal the coexistence of short- and long-range magnetic ordering from the cooperative effect of 1D [CuO4]∞ chains and [CuO2X2] quadrilateral.

Assessing Soil Erosion Risk Through Geospatial Analysis and Magnetic Susceptibility: A Study in the Oued Ghiss Dam Watershed, Central Rif, Morocco

In northern Morocco, water erosion presents a critical risk for soil degradation and dam sedimentation, attributable to extreme climatic conditions, variegated topography, lithological vulnerabilities, and anthropogenic pressures. This study quantitatively and spatially evaluates soil erosion susceptibility within the catchment area of the Oued Ghiss dam in Central Rif, Morocco. Utilizing the Revised Universal Soil Loss Equation (RUSLE) integrated with Geographic Information Systems (GIS) and calibrated through magnetic susceptibility metrics, the study provides a detailed analysis of erosion factors. The model was applied using GIS to spatially analyze data on rainfall, soil type, topography, land cover, and management practices, with magnetic susceptibility measurements used to calibrate the model by identifying stable and erosion-prone areas. The resultant soil loss map reveals a mean erosion rate of 24 t/ha/year. Specifically, 37.28% of the catchment area exhibits an erosion rate under 5 t/ha/year, 40.16% between 5 and 10 t/ha/year, 22.77% between 10 and 20 t/ha/year, and 0.86% surpasses 20 t/ha/year. Magnetic susceptibility measurements across various soil profiles indicated that stable soils showed increased susceptibility towards the surface, while eroded soils displayed decreased susceptibility, with significant correlations found between magnetic susceptibility variations and the final risk map. This innovative calibration of the RUSLE model through magnetic susceptibility improves erosion vulnerability assessments and results in a more detailed soil loss map. The findings provide critical information for policymakers to develop targeted management plans for erosion-prone areas, particularly benefiting the Ghiss dam watershed, where these insights will aid in preventing dam siltation and enhancing water resource management. This confirms magnetic susceptibility's reliability in assessing soil erosion vulnerability and improving numerical models.

Tomonaga-Luttinger liquid and quantum criticality in spin- antiferromagnetic Heisenberg chain C 14 H 18 CuN 4 O 10 via Wilson ratio.

The ground state of a one-dimensional spin- uniform antiferromagnetic Heisenberg chain (AfHc) is a Tomonaga-Luttinger liquid which is quantum-critical with respect to applied magnetic fields up to a saturation field beyond which it transforms to a fully polarized state. Wilson ratio has been predicted to be a good indicator for demarcating these phases [Phys. Rev. B 96, 220401 (2017)]. From detailed temperature and magnetic field-dependent magnetization, magnetic susceptibility and specific heat measurements in a metalorganic complex and comparisons with field theory and quantum transfer matrix method calculations, the complex was found to be a very good realization of a spin- AfHc. Wilson ratio obtained from experimentally obtained magnetic susceptibility and magnetic contribution of specific heat values was used to map the magnetic phase diagram of the uniform spin- AfHc over large regions of phase space demarcating Tomonaga-Luttinger liquid, saturation field quantum critical, and fully polarized states. Luttinger parameter and spinon velocity were found to match very well with the values predicted from conformal field theory.

SYNTHESIS, CHARACTERIZATION AND ANTIBACTERIAL STUDIES ON IRON (II) COMPLEX OF SCHIFF BASE DERIVED FROM ORTHOPHENYLENEDIAMMINE AND 2-NITROBENZALDEHYDE

The synthesis and characterization of Schiff base derived from Orthophenylenediammine and 2-Nitrobenzaldehyde and its Iron (II) complex were undertaken. It was prepared by the condensation reaction of Orthophenylenediammine and 2-Nitrobenzaldehyde. Its Iron (II) metal complex was synthesized by coupling Iron (II) chloride with the formed ligand. These ligands and their complexes were characterized on the basis of their melting point and Decomposition temperature of the Schiff base and metal(II) complexes respectively, infrared spectral analysis, Solubility test, conductivity Test and magnetic susceptibility measurement. The ligand was found to be yellow in colour with a percentage yield of 50% and melting point of 265ºC, The Iron (II) complex was found to be Redish brown in colour with 55% percentage yield and 300ºC decomposition temperature, The ligand and the Iron (II) complex were found to be insoluble in water, n-hexane and Acetone and slightly soluble in methanol and ethanol and completely soluble in Dimethyl sulphoxide, The Iron (II) complex was found to be paramagnetic in nature, A band at 1525cm-1 of the ligand showed that the Aldehyde coordinated with the primary amine.

Crafting copper complexes of variable nuclearity and coordination geometry through solvent tailoring: Unveiling novel structure, magnetic insight and computational marvels

The solvent tuning technique has been employed to synthesize two new copper complexes [Cu3(L)(NO3)2(DMSO)4] (1) and [Cu6(L)2(NO3)2(DMF)4(H2O)2(µ-HCOO)2] (2) which display variable nuclearity and coordination geometries. The synthesized complexes further characterized by using spectroscopic, single crystal and powder X-ray diffraction techniques. Supramolecular assembly of the complexes in the solid state is stabilized by a range of intermolecular interactions including O-H⋅⋅⋅O, C-H⋅⋅⋅O, π⋅⋅⋅π and C-H⋅⋅⋅π. Magnetic susceptibility measurements (χT vs T curves) over a wide range of temperature indicate dominant antiferromagnetic interactions between the Cu(II) centres in both complexes, while DFT calculations reveal the nature and amplitude of the main magnetic interactions. Theoretical study further shows strong antiferromagnetic interactions inside the trimeric units of both complexes as well as both weak ferro- and antiferromagnetic interactions among the trimers. The so-obtained J values have been employed to fit the χT vs T curves, using simplified spin models which correctly reproduce the main features of the experimental curves. Thus, this combined experimental and theoretical study provides insight into the magnetic structure of the copper complexes.

Hydrogen atom abstraction as a synthetic route to a square planar CoII complex with a redox-active tetradentate PNNP ligand.

Redox-active ligands improve the reactivity of transition metal complexes by facilitating redox processes independent of the transition metal center. A tetradentate square planar (PNCH2CH2NP)CoII (1) complex was synthesized and the ethylene backbone was dehydrogenated through hydrogen atom abstraction to afford (PNCHCHNP)CoII (2), which now contains a redox-active ligand. The ligand backbone of 2 can be readily hydrogenated with H2 to regenerate 1. Reduction of 1 and 2 with KC8 in the presence of 18-crown-6 results in cobalt-based reductions to afford [(PNCH2CH2NP)CoI][K(18-crown-6)] (3) and [(PNCHCHNP)CoI][K(18-crown-6)] (4), respectively. Cyclic voltammetry revealed two reversible oxidation processes for 2, presumed to be ligand-based. Following treatment of 2 with one equivalent of FcPF6, the one-electron oxidation product {[(PNCHCHNP)CoII(THF)][PF6]}·THF (5) was obtained. Treating 5 with an additional equivalent of FcPF6 affords the two-electron oxidation product [(PNCHCHNP)CoII][PF6]2 (6). Addition of PMe3 to 5 produced [(PNCHCHNP)CoII(PMe3)][PF6] (7). A host of characterization methods including nuclear magnetic resonance (NMR) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry, magnetic susceptibility measurements using SQUID magnetometry, single-crystal X-ray diffraction, and density functional theory calculations were used to assign 5 and 6 as ligand-based oxidation products of 2.

Metal ion complexes of 2-thioxoimidazolidine-4-one derivatives mixed ligand synthesis, characterization, in-vitro biological activities and in-silico studies

A series of complexes of [Mn (III), Co(II), Cu(II), and Cd(II)] were synthesized with two new 2-thioxoimidazolidin-4-one derivates ligands. These ligands were characterized using an elemental analyzer (CHNS), 1H NMR spectroscopy, FT-IR spectroscopy, and UV–Vis spectroscopy. The synthesized complexes were characterized by magnetic susceptibility measurements, electrical conductance analysis, and atomic absorption spectroscopy. The biological activity of the ligands and complexes were determined against E. coli, B. subtilis, A. niger, and P. chrysogenum. To determine the influence of different metal-ion concentrations on microbial growth, we used molecular docking to evaluate antibacterial activity targeting antimicrobial sites. Our findings indicate that the metal ion complexes exhibited varying degrees of antimicrobial activity, affecting the growth of the tested organisms.

Crystal Growth, Structure, and Diverse Magnetic Behaviors in Frustrated Triangular Lattice REBO3 (RE = Tb-Yb).

Triangular lattice (TL) materials are a rich playground for investigating exotic quantum spin states and related applications in quantum computing and quantum information. Millimeter-level single crystals of REBO3 (RE = Tb-Yb) with a nearly perfect RE-based TL have been successfully grown via a high-temperature flux method and structurally characterized via single-crystal X-ray diffraction. These 113-type materials crystallize in a monoclinic crystal system with a C2/c space group. Anisotropic magnetism and dominant antiferromagnetic interactions are found for the above materials based on DC magnetic susceptibility measurements. The comprehensive low-temperature specific heat data of REBO3 (RE = Tb-Tm) are characterized on single crystals for the first time, which exhibit diverse magnetic behaviors. Specifically, two weak-field-induced transitions could be found in the case of DyBO3 based on the specific heat measurements. Our results suggest that REBO3 (RE = Tb-Yb) is a TL magnetic system for investigating potential quantum magnetism.

Copper (II) halide compounds with cationic N-donor ligands: Design, synthesis, structure and magnetism

Copper (II) complexes of the cationic ligands 1-(4′-pyridyl)-pyridinium (L1) and 1-(4′-pyridyl)-pyridin-4-ol (L2) have been prepared and characterized by single crystal X-ray diffraction and variable temperature magnetic susceptibility measurements: [Cu(L1)2X2]X2 [where X = Cl (1), Br (2)], and [Cu(L2)2X2]X2 [where X = Cl (3), Br (4)]. The complexes are fundamentally square planar with L2X2 coordination planes and long, semi-coordinate bonds to the additional halide ions. All compounds crystallize in monoclinic systems with 1 and 2 in the P21/n space group and 3 and 4 in the P21/c space group. The crystal structures are stabilized by both non-classical (in the case of 1 and 2) and classical (3 and 4) hydrogen bonds. EPR data for 1–4 support a rhombohedral structure, in good agreement with the local geometry as seen in the crystal structures. Magnetic susceptibility measurements show the presence of very weak antiferromagnetic interactions. In addition, the syntheses and magnetic properties of two neutral complexes, [Cu(L3)2X2]·2H2O [L3 = 1-(4′-pyridino)-4-pyridone; X = Cl (5), Br (6)] are reported. Magnetic susceptibility data indicate the presence of moderate antiferromagnetic exchange interactions [J ∼ 28 K (5), 60 K (6)] which were well modeled by the S = 1/2 Heisenberg uniform chain model.

Impact of Synthetic Variables on the Structural Diversity of TbIII-Carboxylate Frameworks: Gas Adsorption, Magnetism, and Organocatalysis Investigations.

In this work, three unique TbIII-carboxylate frameworks with the formula {[Tb2(OH)2(H2O)2(abtc)]·2H2O}n (1), {[Tb2(abtc)1.5(H2O)3(DMA)]·H2O}n (2) and {[Tb3(abtc)2.5(H2O)4]·H3O}n (3), each displaying structural variations, have been successfully synthesized by the solvothermal reactions of Tb(NO3)3·6H2O with the azo-containing ligand 3,3',5,5'-azobenzene tetracarboxylic acid (H4abtc) under varying conditions. Detailed single-crystal X-ray diffraction (SC-XRD) analysis manifested a remarkable diversity in these structures, demonstrating various coordination patterns of TbIII-metal nodes with the carboxylate groups of the organic linker, which contributed to the generation of intricate three-dimensional (3D) coordination networks with remarkable chemical resistance. Furthermore, frameworks 2 and 3, characterized by porous networks containing two and three independent TbIII-metal nodes, respectively, were both demonstrated to be efficient heterogeneous catalysts toward the cyanosilylation of imines under mild conditions with excellent reusability. In addition, direct current (Dc) magnetic susceptibility measurements conducted on frameworks 1, 2, and 3 indicated that there were obvious antiferromagnetic interactions among the TbIII-metal nodes, which suggests the involvement of intricate intra- and intertrimer exchange channels, adding another fascinating dimension to their physical properties.