Magnetic Susceptibility Measurements Research Articles

Cu(II)-Ln(III) (Ln = Gd, Tb and Dy) complexes of an unsymmetrical N2O3 donor ligand: field induced SMM behaviour of Cu(II)-Tb(III) complexes.

Three new hetero-metallic CuII-LnIII complexes [(CuL)Gd(NO3)3(CH3OH)]n (1), [(CuL)Tb(NO3)3(H2O)]·[CuL] (2) and [(CuL)Dy(NO3)3(H2O)]·[CuL] (3) have been synthesized using a mono-nuclear Cu(II) complex, [CuL], of an unsymmetrically di-condensed N2O3 donor Schiff base ligand, N-(3-methoxysalicylidene)-N-(salicylidene)-1,2-ethylenediamine (H2L). Single crystal X-ray crystallography revealed that complex 1 is a nitrate bridged 1D chain of dinuclear Cu(II)-Gd(III) units whereas in 2 and 3, the dinuclear Cu(II)-Ln(III) units are co-crystallized with a [CuL] unit. The Ln(III) centers are nine coordinated with the geometry of a spherical capped square antiprism for Gd and spherical tricapped trigonal prism for Tb and Dy. The geometry of the Cu(II) center is distorted octahedral for complex 1 and distorted square planar for complexes 2 and 3. Temperature-dependent molar magnetic susceptibility measurements in 1-3 revealed the presence of overall ferromagnetic coupling between the Cu(II) and Ln(III) centers. Notably, field induced single-molecule magnet behavior was witnessed in the Tb(III) derivative (2). The ab initio calculations indicated that upon application of an external magnetic field, the tunneling in the ground state of complex 2 gets reduced and thereby field-induced SMM behaviour is observed. Besides, in the case of complex 1, BS-DFT calculations were carried out to gain further insights into the magnetic exchange coupling interactions between the Cu(II) and Gd(III) centers.

Synthesis, disorder and Ising anisotropy in a new spin liquid candidate PrMgAl11O19

Abstract Here we report the successful synthesis of large single crystals of triangular frustrated PrMgAl11O19 using the optical floating zone technique. Single crystal Xray diffraction measurements unveiled the presence of quenched disorder within the mirror plane, specifically ∼7% of Pr ions deviating from the ideal 2d site towards the 6h site. Magnetic susceptibility measurements revealed an Ising anisotropy with the c-axis being the easy axis. Despite a large spin-spin interaction that develops below ∼10 K and considerable site disorder, the spins do not order or freeze down to at least 50 mK. The availability of large single crystals offers a distinct opportunity to investigate the exotic magnetic state on a triangular lattice with an easy axis out of the plane.

Field-Induced Slow Magnetization Relaxation of a Tetrahedral S=2 FeIIS4-Containing Complex.

In the work described herein, the spin relaxation properties of the mononuclear tetrahedral S = 2 [Fe{(SPiPr2)2N}2] complex (1) were studied by employing static and dynamic magnetic measurements al liquid helium temperatures. In the absence of an external direct current (DC) magnetic field, 1 exhibits fast magnetization relaxation. However, in the presence of external magnetic fields of a few kOe, slow relaxation is induced as monitored by alternating current (AC) magnetic susceptibility measurements up to 10 kHz, in the temperature range 2-5 K. Analysis of the temperature dependence of the corresponding relaxation time reveals contributions by Quantum Tunnelling of Magnetization, and the Direct and Orbach processes in the magnetization relaxation mechanism of 1. The energy barrier, Ueff, of the Orbach process, as determined by this analysis, is compared with that related to the zero field splitting parameters of 1 which were previously determined by high- frequency and -field electron paramagnetic resonance and Mössbauer spectroscopies.

Synthesis and Properties of La14TME6CuS24O4, Exhibiting Multivalent Spin Chains (TME = Cr, Fe).

Two homologues in a series of quinary oxysulfides, La14TME6CuS24O4 (TME = Cr or Fe), have been synthesized by solid-state synthesis in sealed ampules, and their structures are homologue to assume a novel crystal structure. X-ray diffraction analyses of single crystal and powder samples give a monoclinic lattice, described in the C2/m (No. 12) space group, with lattice parameters a = 15.3853(5) Å, b = 13.9729(5) Å, c = 10.5074(4) Å, and β = 116.227(3)° for the Cr analogue and a = 15.4303(2) Å, b = 14.0033(2) Å, c = 10.4909(2) Å, and β = 116.261(2)° for Fe. The crystal structure contains one-dimensional (1D) chains consisting of interconnected transition metal element (TME) trimers, which are further arranged into two-dimensional (2D) layers. These spin-chain planes are interspaced with 1D chains of lanthanum-oxygen coordinations and an apparent disordered occupation of copper sites. Alternating current (AC) and direct current (DC) magnetic susceptibility measurements show that the Cr and Fe analogues exhibit what is best described as spin-domain formation. Density functional theory (DFT) calculations suggest the formal oxidation state of the species is best represented in the form La14TME52+TME3+Cu+S24O4.

Low-temperature behaviors of the dipolar magnet Dy3Sb3Zn2O14 with a strongly site-mixing disordered kagome lattice

Interesting behaviors may emerge in the magnetic frustrated materials with significant site-mixing disorder. We present the results of the structural, magnetic susceptibility, and specific heat measurements of Dy3Sb3Zn2O14 with ∼20 % Dy/Zn site-mixing disorder, which results in either a diluted 2D triangular lattice, or an intermediate structure between the kagome and pyrochlore lattice. In addition to the sharp anomaly of the temperature dependence of specific heat at T∼ 0.35 K, which was attributed to the emergent charge order state for the sample with less disorder, a broad peak at T∼ 1.5 K, and a small hump below T∼ 0.1 K are observed. The measured temperature dependence of specific heat and the Monte Carlo simulation suggest that the magnetic frustration persists despite of a strong site-mixing disorder.

Chiral Heterometallic Cu8Ln4 Complexes with Enantiopure Schiff Base Ligands: Synthesis, Structural, Spectroscopic and Magnetic Studies.

The enantiomerically pure Schiff base ligands H2L-S and H2L-R yield chiral heterometallic dodecanuclear complexes of the form [Cu8Ln4(OH)8(OMe)4(O2CBut)8(L-S or L-R)4(H2O)4] where LnIII=Gd (1S), Tb (2S), Dy (3S, 3R), Ho (4S, 4R), Er (5S) or Y (6S, 6R) and H2L=(S or R)-2-{[(1-hydroxypropan-2-yl)imino]methyl}-6-methoxyphenol. The complexes are isomorphous and crystallize in the non-centrosymmetric polar space group C2 in enantiomeric conformation. The chirality of the Schiff base ligands originates from the respective S- or R- enantiomer of 2-aminopropan-1-ol, is imparted to the complexes and to the crystals that belong to non-centrosymmetric space group. The chirality and enantiomeric conformation of all complexes are retained in dmso solutions as confirmed by Circular Dichroism spectra which consist of mirror images, expected for enantiomeric pairs. All complexes consist of four distorted cubane-like subunits [Cu2Ln2(μ3-OH)2(μ3-OMe)(μ3-OR)], which share the LnIII ions and result in a cyclic distorted tetragonal arrangement; each edge of the {LnIII 4} quadrilateral is occupied by two μ-OH- ions that further bridge to a CuII ion. Magnetic susceptibility measurements revealed ferromagnetic interactions for 3S with LnIII=Dy and antiferromagnetic interactions for all other complexes. AC susceptibility data of 3S under 1 kOe external dc field indicate slow magnetic relaxation phenomena below 2 K.

High-resolution luminescence-dated sediment record for the last two glacial-interglacial cycles from Rodderberg, Germany

The Rodderberg Volcanic Complex (RVC) is well-known for the long climate record archived in its crater basin, which lasts for several glacial-interglacial cycles. However, a detailed chronological framework is still lacking. Here, we perform high-resolution luminescence dating on a 72.8 m-long sediment core with the optically stimulated luminescence (OSL) signal from fine-grained (4–11 μm) quartz and three kinds of post-infrared infrared (pIRIR) stimulated luminescence signals from fine-grained polymineral fractions. Together with magnetic susceptibility, grain size and quartz OSL sensitivity measurements, a numerical age framework is built for the upper half of the sediment core. Quartz OSL ages align well with pIRIR ages for the last 45 ka, but they underestimate in relation to pIRIR ages for ages beyond 45 ka. The three pIRIR signals, including the pIRIR signal at 225 °C (pIRIR225), the pulsed pIRIR signal at 150 °C (pulsed pIRIR150) and the multi-elevated-temperature pIRIR at 250 °C (MET-pIRIR250), yield consistent ages up to ca. 250 ka at a sediment depth of 37.5 m. Below that depth, dating limits of the protocols are reached. Nevertheless, our results indicate that sediments below 37.5 m predate Marine Isotope Stage (MIS) 7. Altogether, obtained ages reveal continuous dust accumulation during MIS 7 and MIS 6. One erosional event happened at the end of the Eemian (MIS 5e), which eroded the Eemian soil. The sedimentation rate during the Weichselian glacial period is tenfold lower compared to the sedimentation rate observed during MIS 7–6. This low sedimentation rate likely arises from the cessation of slope wash effects and the occurrence of various wind erosional events alternating with dust deposition as the basin is filled by dust. A notably high sedimentation rate is observed at the transition from MIS 6 to the Eemian, marked by the deposition of a 7 m-thick loess layer between 135–129 (±5) ka. This high sedimentation rate could be attributed to intensified slope wash and solifluction processes resulting from the thawing of permafrost at the time of deglaciation. Alternatively, it might be a signature of Heinrich event 11, during which strong winds brought large amounts of dust into the basin within a short time.

Epitaxial growth and stoichiometry control of pyrochlore Nd2Ru2O7 thin films

We report on the epitaxial growth of pyrochlore NRO thin films utilizing a reactive off-axis sputtering technique. The growth process employed Ru and Nd metal targets with a repetitive substrate temperature sequence. X-ray diffraction, magnetic susceptibility, and spectroscopic ellipsometry measurements confirm that the structural, magnetic, and electronic properties of near-stoichiometric NRO films match those of the bulk material. Our spin-polarized density functional calculations based on Nd2Ru2O7 structural parameters accurately describe the optical spectra and assign Hubbard bands to the interband transitions observed above the optical band gap of 0.2 eV. By utilizing the technique's capability to adjust the degree of ruthenium deficiency, we investigated Nd2Ru2O7 films across a wide range of stoichiometric variations. Decreasing the Ru/Nd ratio results in lattice expansion, an increase in the optical band gap, and the suppression of Ru 4d intersite optical transitions. Additionally, this adjustment facilitates the elimination of minor inclusions of a ferromagnetic NdOx impurity phase, influencing the magnetic properties of stoichiometric films at low temperatures. The successful growth of Nd2Ru2O7 films opens up promising opportunities for designing and exploring strain- and light-induced states in pyrochlore ruthenates. Published by the American Physical Society 2024

B-diketon Derived Ligands Metal Complexes, Synthesize, Characterization, and Bioactivity Studies

The precursor in our study 2, 2’- ((1E,1’E) - (4,4’- diamino - 5, 5’- dimethyl - [1,1’-biphenyl]-3, 3’-diyl) bis(diazene-2,1-diyl) diphenol (W1) or (W2) 3,3’-dimethyl-5,5’-bis((E)-pyridin-3-yldiazenyl)-[1,1’-biphenyl]-4,4’-diamine were obtained from reaction of diazonium salt with tolidin. The both precursors used for synthesis of the ligands [H4L1] and [H2L2] by reaction with di benzyl methan to produce the ligands [H4L1]2,2’-((1E,1’E)-(4,4’-bis((3-hydroxy-1,3-diphenylpropylidene)amino)-5,5’-dimethyl-[1,1’-biphenyl]-3,3’-diyl)bis(diazene-2,1-diyl))diphenoland [H2L2] 3,3’-((3,3’-dimethyl-5,5’-bis((E)-pyridin-3-yldiazenyl)-[1,1’-biphenyl]-4,4’-diyl)bis(azaneylylidene))bis(1,3-diphenylpropan-1-ol). Elemental microanalysis, 1H and 13C-NMR, FT-IR, U.V, mass spectroscopies were used to describe the structure of the ligands. In this research we also reported the complexes synthesis via reaction of of [NiII, MnII, CoII, CdII, CuII] chloride salts with ligands, using KOH as a base and ethanol as a solvent, under reflux. Complexes were characterized by atomic absorption, (FT-I.R, U.V-Vis, 1H and 13C-NMR and mass) spectroscopies along with conductivity, magnetic susceptibility and melting point measurements. The presence of crystallized water molecule insured by thermal analysis in some complexes structure. Finally, the synthesized ligands and complexes biological activity studied against selected organisms.

Antiferromagnetic resorcinol bridged dinuclear square-planar copper (II) complexes: Syntheses, structural, spectroscopic and magnetic properties

A new C2-symmetric Schiff base ligand (H2L) featuring a core resorcinol bridging unit has been created, utilizing the Duff formylation reaction followed by the Schiff base condensation reaction. The ligand was characterized by various spectroscopic techniques.. Cu(II) salts with varying coordinating anions (Cl− and SCN−) in methanol were allowed to react with this ligand in a 2:1 M ratio to create dinuclear Cu(II) complexes. The complexes were isolated in pure form and characterized by, elemental analysis,single crystal X-ray crystallography and various spectroscopic techniques. X-ray analysis discloses that both complexes are dinuclear, where the ligand (H2L) being tridentate in nature, coordinates to Cu(II) through its two N donor atoms and one O donor atom in the equatorial positions. The respective anions (−Cl− for 1 and –SCN− for 2) coordinate to Cu(II) to complete its square planar geometry. Temperature dependent magnetic susceptibility measurements indicate weak antiferromagnetic exchange interactions with a coupling constant of J = −5.9(1) cm−1 and g = 2.148(1) for 1 and J = −10.08(1) cm−1 and g = 2.106(1) for 2.

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.