Weak Antiferromagnetic Interactions Research Articles

Paramagnetic ionic liquid crystals: Ion conductive bent-core derivatives of stable radicals

A series of bent-core paramagnetic ionic liquid crystals derived from stable radicals, 6-oxoverdazyl and 1,4-dihydrobenzo[e][1,2,4]triazin-4-yl, and containing the N-methylimidazolium group were prepared and their mesogenic, magnetic and ion conductive properties were investigated. The ion pairs form fluid smectic phases above 100 °C, in which ionic layers are separated by paramagnetic layers. Ion conductivity for two selected derivatives is in a range of 10-5 –10-8 S cm−1 and activation energies Ea are about 1.5 eV. Magnetic susceptibility measurements (SQUID) of pristine solid samples revealed liquid-like molecular arrangement in the paramagnetic layers and weak antiferromagnetic interactions.

Nickel(II) complexes with 2-Hfur and N-donors: The magnetic effects of the structural variations, thermal properties and antimycobacterial activity against Mycolicibacterium smegmatis

New complexes of nickel(II) with 2-furoic acid (2-Hfur) and different N-donor ligands of the composition [Ni(fur)2(phen)(H2O)2]·H2O (1) (phen = 1,10-phenantroline), [Ni(fur)2(2,2′-bpy)] (2, 2,2′-bpy = 2,2′-bipyridine), [Ni(fur)2(4,4′-bpy)(CH3OH)2]n (3, 4,4′-bpy = 4,4′-bipyridine), [Ni(fur)2(pz)4]·2MeCN (4) (pz = pyrazole) have been synthesized. The structure of the compounds was established by single crystal X-ray diffraction analysis. Complexes 1, 2, and 4 are mononuclear, complex 3 is a 1D coordination polymer. The DC magnetic susceptibility data measured for 2 and 3 are indicative of antiferromagnetic exchange interactions between the metal centers, which proved to be negligibly weak in 2 and more pronounced in 3. A quantum-chemical analysis of intermolecular (for 2) and intra- and interchain (for 3) magnetic exchange pathways confirms these findings, revealing the presence of magnetic chains formed by a network of very weak intermolecular antiferromagnetic exchange interactions in the crystal of 2 and a strengthening of antiferromagnetic exchange coupling in the polymeric chains of 3. Thermal behavior of 1 and 2 was studied by simultaneous thermal analysis (STA). According to PXRD data, the final thermolysis product of complex 2 is metal Ni nanocrystals (d = 14.7(3) nm). Analysis of the results of biological activity of 1–4in vitro against Mycolicibacterium smegmatis showed a low sensitivity of the mycobacterial wall to Ni2+ cations.

Europium(III), Terbium(III), and Gadolinium(III) Oxamato-Based Coordination Polymers: Visible Luminescence and Slow Magnetic Relaxation.

The reaction of aqueous solutions of EuIII, TbIII, and GdIII ions with Na2Hpcpa [H3pcpa = N-(4-carboxyphenyl)oxamic acid] afforded three new isostructural oxamate-containing lanthanide(III) coordination polymers of general formula {LnIII2(Hpcpa)3(H2O)5·H2O}n [Ln = Eu (1),Tb (2), and Gd(3)]. Their structure is made up of neutral zigzag chains running parallel to the [101] direction where double syn-syn carboxylate(oxamate)-bridged dilanthanide(III) pairs (Ln1 and Ln2) are linked by three Hpcpa2- ligands, one of them with the μ-κ2O,O':κO″ coordination mode and the other two with the μ3-κ2O,O':κO″:κO'''. Additionally, two of those chains are interlinked through hydrogen bonding and π-π type interactions, resulting in a porous structure with channels where water molecules are hosted. The emission properties of 1 and 2 are evaluated as a function of the temperature, exhibiting an emission in red and green, respectively. The external quantum yield for 2 is approximately 7 times that obtained for 1, indicating that the oxamate ligand is a better sensitizer for TbIII ions. The temperature dependence of the dc magnetic properties of 1-3 reveals a different magnetic behavior depending on the nature of the LnIII ion. A continuous decrease of χMT occurs for 1 upon cooling, and finally χMT tends to vanish, as expected for the thermal depopulation of the six magnetic 7FJ excited states (J = 1-6) of the EuIII ion with a nonmagnetic 7F0 ground state. χMT for 2 decreases sharply with decreasing the temperature due to the depopulation of the splitted mJ levels of the 7F7 ground state of the magnetically anisotropic TbIII ion. A very weak antiferromagnetic interaction between the magnetically isotropic GdIII ions across the double carboxylate(oxamate) bridge is responsible for the small decrease of χMT at low temperatures for 3. The dynamic (ac) magnetic properties of 2 and 3 reveal a slow magnetic relaxation with very incipient frequency-dependent χM″ signals below 6.0 K (2) and frequency-dependent χM″ peaks below 10.0 K (3) under nonzero applied dc magnetic fields, being thus new examples of field-induced single molecule magnets (SMMs).

Synthesis, structures, photoluminescence and magnetic properties of three dinuclear lanthanide(III) complexes derived from 4‐fluorophenylselenoacetic acid

AbstractThree novel dinuclear lanthanide(III) complexes [Ln2L6(phen)2] (Ln=EuIII (1), TbIII (2), Dy III (3)), derived from 4‐fluorophenylselenoacetic acid and 1,10‐phenanthroline, have been synthesized and characterized by elemental analysis, IR, TGA, powder X‐ray diffraction and single‐crystal X‐ray diffraction analysis. Single crystal X‐ray diffraction reveal they are isostructural and crystallize in the monoclinic crystal system, space group P2(1)/c. The investigations on luminescent properties of Eu(III) complex 1 and Tb(III) complex 2 exhibit the characteristic emissions of EuIII (5D0→7F0‐4) and TbIII (5D4→7F6‐3), and the corresponding luminescent lifetimes are 1.52 and 1.10 ms, respectively. Temperature‐dependent photoluminescence studies show the emission intensities and lifetimes for both complexes decrease upon increasing temperature, which indicates complexes 1 and 2 have the potential for sensing temperature. The magnetic studies reveal that Dy(III) complex 3 exhibits weak antiferromagnetic interactions and slow magnetic relaxation behavior.

Mono- and Binuclear Copper(II) and Nickel(II) Complexes with the 3,6-Bis(picolylamino)-1,2,4,5-Tetrazine Ligand.

Four new compounds of formulas [Cu(hfac)2(L)] (1), [Ni(hfac)2(L)] (2), [{Cu(hfac)2}2(µ-L)]·2CH3OH (3) and [{Ni(hfac)2}2(µ-L)]·2CH3CN (4) [Hhfac = hexafluoroacetylacetone and L = 3,6-bis(picolylamino)-1,2,4,5-tetrazine] have been prepared and their structures determined by X-ray diffraction on single crystals. Compounds 1 and 2 are isostructural mononuclear complexes where the metal ions [copper(II) (1) and nickel(II) (2)] are six-coordinated in distorted octahedral MN2O4 surroundings which are built by two bidentate hfac ligands plus another bidentate L molecule. This last ligand coordinates to the metal ions through the nitrogen atoms of the picolylamine fragment. Compounds 3 and 4 are centrosymmetric homodinuclear compounds where two bidentate hfac units are the bidentate capping ligands at each metal center and a bis-bidentate L molecule acts as a bridge. The values of the intramolecular metal···metal separation are 7.97 (3) and 7.82 Å (4). Static (dc) magnetic susceptibility measurements were carried out for polycrystalline samples 1–4 in the temperature range 1.9–300 K. Curie law behaviors were observed for 1 and 2, the downturn of χMT in the low temperature region for 2 being due to the zero-field splitting of the nickel(II) ion. Very weak [J = −0.247(2) cm−1] and relatively weak intramolecular antiferromagnetic interactions [J = −4.86(2) cm−1] occurred in 3 and 4, respectively (the spin Hamiltonian being defined as H = −JS1·S2). Simple symmetry considerations about the overlap between the magnetic orbitals across the extended bis-bidentate L bridge in 3 and 4 account for their magnetic properties.

Synthesis, structure, and magnetic properties of a family of Mn(II) compounds with substituted 2-aminopyridinium ions

A family of complexes were made by combining MnX2·nH2O (X = Cl, Br) with 2-amino-3-methylpyridine (3MAP), 2-amino-5-methylpyridine (5MAP) or 2-amino-5-iodopyridine (5IAP) in aqueous acidic conditions. The resulting complexes were (3MAPH)2Cl2.MnCl2(H2O)2 (1), (3MAPH)2Br2.MnBr2(H2O)2 (2), (5IAPH)8 [Mn4Cl10(H2O)8] Cl6 (3) and (5MAPH)2 MnBr4 (4). Complexes 1–3 crystalize in monoclinic space groups (1 = P21/c, 2&3 = P21/n) with chains formed by halide bridged manganese ions. Compound 4 crystalizes in the triclinic space group P-1 with a manganese halide ladder structure formed via short Br…Br contacts. Complexes 1, 2 and 4 were studied through variable temperature magnetic susceptibility measurements, all of which exhibited weak antiferromagnetic interactions (J = ~ – 0.45 to –0.05 K).

Structures and magnetic properties of five lanthanide-radical complexes constructed by 8-methoxyquinoline substituted tridentate chelating nitronyl nitroxide radical

Five lanthanide complexes [Ln(hfac)3(8-MeOTQ-2-NIT)] constructed by a tridentate chelating 8-methoxyquinoline substituted nitronyl nitroxide radical (Ln ​= ​Gd (1), Tb (2), Dy (3), Ho (4), Er (5), hfac ​= ​hexafluoroacetylacetonate, 8-MeOTQ-2-NIT ​= ​2-(8-methoxyquinoline)-4,4,5,5- tetra-methylimidazoline-1-oxyl-3-oxide) have been successfully synthesized and characterized. The five complexes have similar mononuclear two-spin structures with one LnIII ion and one radical (Rad) in the molecules. And all LnⅢ ions are nine-coordinated in the geometry between mono-capped square antiprism (C4v) and a trigonal bipyramidal (D3h). Alternating current magnetic studies show that Tb and Dy complexes display frequency dependence of out of phase signals indicating the slow magnetic relaxation behavior of single molecular magnets. The ferromagnetic interactions in Gd/Tb-Rad complexes and the very weak antiferromagnetic interactions in Dy/Ho/Er-Rad complexes were estimated by the rough model combining lanthanide single ions approximation and molecular-field approximation.

Copper(II) Carboxylates with 2,3,4-Trimethoxybenzoate and 2,4,6-Trimethoxybenzoate: Dinuclear Cu(II) Cluster and µ-Aqua-Bridged Cu(II) Chain Molecule

Copper(II) complexes with 2,3,4-trimethoxybenzoic acid (H234-tmbz) and 2,4,6-trimethoxybenzoic acid (H246-tmbz), [Cu2(234-tmbz)4(H2O)2] (6) and [Cu(246-tmbz)2(µ-H2O)2(H2O)2]n (7), were synthesized and characterized by elemental analysis, infrared and UV-vis spectra and temperature dependence of magnetic susceptibilities (1.9–300 K). The X-ray crystal structures revealed that the former 6 is a dinuclear cluster having syn-syn-bridged Cu2(µ-234-tmbz)4 core with Cu···Cu separation of 2.6009(7) Å, while the latter 7 is a µ-aqua-bridged chain molecule consisting of Cu(246-tmb)2(µ-H2O)2(H2O)2 units with Cu···Cu separation of 4.1420(5) Å. Temperature dependence of magnetic susceptibilities showed that an antiferromagnetic interaction with 2J = −272 cm−1 for 6 and a weak antiferromagnetic interaction with J = −0.21 cm−1 for 7, between the two copper(II) ions. The adsorption isotherm of 6 showed Types I behavior having a 125.4 m2g−1 of specific surface area.

Strong Equatorial Crystal Field Enhances the Axial Anisotropy and Energy Barrier for Spin Reversal Process in Yb2 Single Molecule Magnets.

The importance of equatorial crystal fields on magnetic anisotropy of ytterbium single molecule magnets (SMMs) is observed for the first time. Herein, we report three similar dinuclear ytterbium complexes with the formula [Yb2 (3-OMe-L)2 (DMF)2 (NO3 )2 ]⋅DMF (1), [Yb2 (3-H-L)2 (DMF)2 (NO3 )2 ]⋅DMF⋅H2 O (2), and [Yb2 (3-NO3 -L)2 (DMF)2 (NO3 )2 ] (3), [where 3-X-H2 L=N'-(2-hydroxy-3-X-benzylidene)picolinohydrazide, X=OMe (1), H (2) NO2 (3)]. Detailed magnetic measurements reveal the presence of weak antiferromagnetic interactions between the Yb centers and a field-induced slow relaxation of magnetization in all complexes. A higher energy barrier for spin reversal was observed for complex 1 (Ueff =50 K) and it decreases in the order of 2 (47 K) to 3 (40 K). Notably, complex 1 shows a remarkable energy barrier within the frequency range of 1-850 Hz reported for Yb-based SMMs. Further, ab initio calculations show a higher axial anisotropy and lower quantum tunneling of magnetization (QTM) in the ground state for 1 compared to 2 and 3. It was also observed that the presence of a strong crystal field in the equatorial plane (when the ∡ O1-Yb-O3 bond angle is close to 90°) enhances the axial anisotropy and improves the SMM behavior in the studied complexes. Both the experimental and theoretical analysis of relaxation dynamics discloses that Raman and QTM play major role on slow relaxation process for all complexes. To provide more insight into the exchange interactions, broken-symmetry DFT calculations were performed.

Structures and magnetic properties of acyloxy-O bridged Ln2 compounds: Gd2 compound displaying magnetic refrigeration property

In order to study magnetocaloric effect, we synthesized five new dinuclear lanthanide (Ⅲ) compounds, namely [Ln(dbm)2HL(CH3OH)]2•2CH3OH (LnⅢ=Nd(1), Gd(2) and Tm(5), dbm =1,3-diphenylpropane-1,3‑dione, HL = N'-[(1E)-[5-(hydroxymethyl)furan-2-yl]methylidene]pyrazine-2-carbohydrazide) and [Ln(dbm)2HL]2 (LnⅢ = Ho(3) and Er(4)), and characterized by elemental analysis, IR, PXRD, UV–vis and single crystal X-ray diffraction. The structures of compounds 1–5 are very similar with a planar [Ln2O2]. Magnetic studies indicated that weak antiferromagnetic interaction are present between the Gd(Ⅲ) ions within 2. Meanwhile, Gd2 compound displays magnetic refrigeration property with the max entropy change (-ΔSm) of 16.58 J K − 1kg−1 (T = 2.0 K and ΔH = 70 kOe).

A novel single-pot synthesis of dinuclear and mononuclear copper(II) complexes with sterically demanding Schiff bases: Structural, spectral, magnetic, electrochemical, DNA binding and theoretical investigation

Two dinuclear CuII complexes, cyclo[Cu2(LtBu)Cl2]·4EtOH] (monoclinic P21/n) (2) and cyclo[Cu2(LMe)1.5Cl·0·5H2O]Cl·(H2O) (hexagonal P6) (3) (where cycloH2LtBu = cyclobis{2-[benz(N-ethan-1,2-diyl)imidoyl][6-benzimidoyl][4‑tert‑butyl]phenol}, and cycloH2LMe = cyclobis{2-[benz(N-propan-1,3-diyl)imidoyl][6-benzimidoyl][4-methylphenol}, and two mononuclear CuII complexes, [Cu(LtBu)(OH2)] (monoclinic P21/c) (4) and [Cu(mdbp)2] (monoclinic P21/c) (5) (where H2LtBu = bis[2-{6-benzoyl-4‑tert-butylphenol}benzimidoyl]-1,3-propane; mdbpH = 4-methyl-2,6-dibenzoylphenol) have been synthesized by a one–pot condensation involving CuII chloride, ethane-1,2-diamine, propane-1,3-diamine, 4-methyl-2,6-dibenzoylphenol (mdbpH) and 4‑tert‑butyl‑2,6-dibenzoylphenol (bdbpH). The macrocyclic Schiff bases, cyclo[H2LtBu] and cyclo[H2LMe], and the tetradentate Schiff base [H2LtBu], and 2 – 5, have been characterised by elemental analysis, conductivity measurements, mass spectrometry, IR, electronic, 1H and 13C NMR, and ESR spectroscopy, cyclic voltammetry, X-ray crystallography and variable temperature magnetic susceptibility. In 2 and 3, the macrocyclic N4O2 ligand wraps around square pyramidally coordinated copper in a binuclear phenoxo bridged complex. In 2 the apical chlorine atoms are trans with respect to the macrocyclic ligand whereas in 3 they are cis. In the crystalline solid Cl and H2O are disordered on one of the axial positions. Variable temperature magnetic properties indicate weak antiferromagnetic interactions in 1, 2 and 3. Mononuclear complex 4 possesses a tetradentate ONNO ligand with a square pyramidal configuration at Cu and H2O directed at the apical position. Complexes 2 and 3, and 5 are, respectively, examples of square pyramidal and square planar coordinated copper. Density functional theory (DFT) calculations for gas-phase complexes 1, 2, 3, 4 and 5 provide descriptions of electronic properties that are compared with spectroscopic, electrochemical and DNA binding measurements. The binding constants to calf thymus DNA decrease in the order, 2 > 4 > 3 >1 > 5.

Magnetic and electronic structures of antiferromagnetic topological material candidate EuMg2Bi2

EuMg2Bi2 has been investigated to understand the electronic and magnetic behaviors as an antiferromagnetic (AFM) topological semimetal candidate. High-quality single crystals of EuMg2Bi2 were grown via a Bi flux and, subsequently, characterized to be consistent with the previously reported bulk magnetic and resistivity properties. A ferromagnetic interaction is indicated by the positive Curie–Weiss temperature obtained through fitting the bulk magnetic susceptibility data. The bulk resistivity measurements reveal an interesting electronic behavior that is potentially influenced by a competing antiferromagnetic and ferromagnetic interaction in and out of the ab plane. From the resulting refinement of the neutron diffraction data, EuMg2Bi2 was found to exhibit an A-type magnetic structure with Eu2+ moments ferromagnetically aligned in the plane and antiferromagnetically stacked between neighbor ferromagnetic Eu layers. The power law fitting magnetic ordering parameter below TN ∼ 8 K agrees with the 2D Heisenberg model, indicating a weak interlayer antiferromagnetic interaction. Considering the magnetic structure determined by neutron diffraction, the surface state calculation suggests that EuMg2Bi2 is an AFM topological insulator candidate. Linearly dispersed Dirac surface states were also observed in our angle-resolved photoemission spectroscopy measurements, consistent with the calculation.

Crystal Structure and Magnetic Properties of 3,5-Pyridinedicarboxylate-Bridged Re(Ii)M(Ii) Heterodinuclear Complexes (M = Cu, Ni and Co)

The use of the mononuclear rhenium(II) precursor NBu 4 [Re(NO)Br 4 (H 2 pydc)]· i -PrOH ( 1 ) (H 2 pydc = 3,5-pyridinedicarboxylic acid) as a metalloligand towards Cu(II), Ni(II) and Co(II) afforded three new heterobimetallic complexes [Re(NO)Br 4 (μ-Hpydc)Cu(4,4’-dmbipy) 2 ]·(CH 3 ) 2 CO·0.25MeCN ( 2 ), [Re(NO)Br 4 (μ-Hpydc)Ni(dmphen) 2 ]·MeCN ( 3 ) and [Re(NO)Br 4 (μ-Hpydc)Co(dmphen) 2 ]·2H 2 O ( 4 ), respectively [4,4’-dmbipy = 4,4’-dimethyl-2,2’-bipyridine, dmphen = 2,9-dimethyl-1,10-phenanthroline and n -Bu 4 N + = tetra- n -butylammonium]. The crystal structures of 1 and 2 are reported herein together with the cryomagnetic investigation of 1 - 4 in the temperature range of 2.0-300 K. 1 is a mononuclear compound whose structure is made of [Re(NO)Br 4 (H 2 pydc)] - complex anions, tetra- n -butylammonium cations and isopropanol molecules of crystallization. Each rhenium(II) ion in 1 is six-coordinate with four bromide ligands in the equatorial positions and a nitrosyl group and one pyridyl-nitrogen atom from an H 2 pydc ligand filling the axial sites. 2 is a neutral heterobimetallic compound where the [Re(NO)Br 4 (Hpydc)] 2- complex anion acts as a monodentate ligand towards the [Cu(dmphen) 2 ] 2+ complex cation through one carboxylate-oxygen atom. The rhenium(II) ion is six-coordinate in a somewhat distorted octahedral surrounding similar to that in 1 . The copper(II) ion in 2 is five-coordinate with four nitrogen atoms from two bidentate 4,4’-dmbipy ligands and one carboxylate-oxygen atom, describing a surrounding intermediate between square pyramidal and trigonal bipyramidal. Compound 1 behaves as a quasi-magnetically isolated spin doublet with weak antiferromagnetic interactions through space Br⋯Br contacts, ligand field, spin-orbit coupling, tetragonal distortion, and covalence effects considered as variable parameters in a successful simulation of the magnetic data . Compounds 2 – 4 exhibit also weak intramolecular antiferromagnetic interactions ( J ) covering the range -0.60(1) to -1.50(1) cm -1 with the Hamiltonian being defined as H = - J S Re S M , M = Cu ( 2 ), Ni ( 3 ) and Co ( 4 ).

Copper(II) Complexes of 1,3-Dimethyl-5-(4'/3'-pyridylazo)-6-aminouracil: Structures, Redox, Magnetic and Protein Binding Properties

Two new monomeric copper(II) complexes based on 1,3-dimethyl-5-(4'/3'-pyridylazo)-6-aminouracil (HL1: 4'-pyridylazo, complex 1: cis-CuIIL12.MeOH; HL2: 3'-pyridylazo, complex 2: cis-CuIIL12.H2O) were synthesized, characterized and investigated for redox, magnetic and protein-binding properties. The complex 1 is in monoclinic space group C2/c, Z = 4 whereas the complex 2 is in triclinic space group P-1, Z = 2. The complexes hold similar structure in solid and solution state as could be infered from the EPR spectra of 1 having well-resolved hyperfine features, g|| > g┴ > ge (g|| =2.20 and g┴ =2.05). The E½ values for oxidative response of Cu(III)/Cu(II) couple are 1.030 V (ΔE = 133 mV) for 1 and 0.982 V (ΔE = 128 mV) for 2, indicating high redox stability of Cu(II) ions in the complex environment. Direct current (DC) variable-temperature magnetic susceptibility measurements on polycrystalline sample of 1 were carried out in the temperature range 1.8-300 K. The magnetic behavior indicates a weak antiferromagnetic interaction between Cu(II) ions in the crystal lattice below 25 K. The study of Bovin Serum Albumin (BSA)-complex interactions reveals that the BSA binds the complexes through the sites of tryptophan residues in 1:1 manner (n = 0.9007 & KA = 1.482 × 104 M-1 for 1 and 0.7433 & KA =2.394×103 M-1 for 2). Thus, the developed complexes could be treated as muti-functional materials.

Heterometallic supramolecular architectures constructed from cyanido-based [CoIII(AA)(CN)4]- building-blocks (AA = 1,10-phenantroline and 2,2’-bipyridine)

A neutral, mixed-valence cyanido-bridged {Co2IICo2III} complex, with formula {[CoII2(L)(MeOH)2][CoIII(phen)(CN)4]2}·2H2O·0.5MeOH (1), and a cyanido-based ionic compound, with formula [MnII(MAC)(H2O)2][CoIII(bipy)(CN)4]2·3H2O (2) were obtained by reacting the heteroleptic Ph4P[CoIII(AA)(CN)4] building-block [AA = 1,10-phenanthroline, phen, (1) and 2,2’-bipyridine, bipy, (2)] with the dinuclear {Co2IIL}2+ (1) and mononuclear {MnII(MAC)}2+ (2) precursors, respectively [H2L = macrocyclic Schiff-base obtained by condensation of 2,6-diformyl-p-cresol with 1,3-diaminopropane and MAC = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo-[12.3.1]octadeca-(18),2,12,14,16-pentaene]. The structures of 1 and 2 were determined by X-ray diffraction on single crystals. 1 is a neutral tetranuclear homometallic compound where two peripheral [CoIII(phen)(CN)4]- entities which act as end-cap ligands through one of its four cyanide groups towards the inner double phenoxido-bridged [Co2II(L)(MeOH)2]2+ dinuclear unit. Both cobalt(III) and cobalt(II) ions are six-coordinate with two phenanthroline-nitrogen and four cyanide-carbon atoms (at CoIII) and two phenoxido-oxygens and two imino-nitrogen atoms from the Schiff-base ligand plus a methanol molecule and a cyanide-nitrogen atom (at CoII) building somewhat distorted octahedral surroundings. The value of the cobalt(II)×××cobalt(II) separation is 3.11 Å and that of the angle at the phenoxo bridge is 99.4°. Compound 2 is a heterobimetallic ionic salt which is made up of [CoIII(bipy)(CN)4]- anions and [Mn(MAC)(H2O)2]2+ cations. Each cobalt(II) in 1 is six-coordinated, in a distorted octahedral environment built by a bidentate bipy ligand and four monodentate cyanide groups whereas the manganese(II) ion is seven-coordinated with five nitrogen atoms of the MAC ligand and two water molecules describing a distorted pentagonal bipyramid surrounding. The cryomagnetic investigation of 1 in the temperature range 1.9-300 K reveals the occurrence of strong spin-orbit coupling effects and a relatively weak antiferromagnetic interaction between the high-spin cobalt(II) ions linked by the double phenoxido bridge . The nature and magnitude of the magnetic coupling in 1 compares well with those from previous magneto-structural studies on the CoII2O2 motifs where antiferromagnetic interactions result in the examples having values at the phenoxido angle larger than 99.7º with dihedral angles smaller than 35.3°.

An electrically conducting molecular crystal composed of a magnetic iron(iii) complex (S = 1/2) with a large aromatic ligand, 1,2-naphthlalocyanine (C4h isomer): towards the development of molecular spintronics.

The field of molecular spintronics has gained significant attention for the development of second-generation spintronic devices. Therefore, an electrically conducting molecular crystal, Ph4P[FeIII(1,2-Nc)(CN)2]2 (Ph4P = tetraphenylphosphonium and 1,2-Nc = C4h isomer of 1,2-naphthalocyanine), was fabricated as a new coordination compound with a strong π-d interaction. Furthermore, it is a mixed-valence compound with a local spin of S = 1/2 at the center of the conduction path. Crystal structure analysis revealed that Ph4P[FeIII(1,2-Nc)(CN)2]2 was isostructural to its non-magnetic analogue Ph4P[CoIII(1,2-Nc)(CN)2]2 but possessed higher electrical resistivity, indicating that the strong intramolecular π-d interaction is present in the [FeIII(1,2-Nc)(CN)2] unit. Although the magnetic interaction between π-conduction electrons and FeIII-d spins (π-d interaction) is crucial for the emergence of a negative magnetoresistance effect, the negative magnetoresistance effect of Ph4P[FeIII(1,2-Nc)(CN)2]2 was significantly smaller (-6% at 30 K under a static 9 T magnetic field) than those of Ph4P[FeIII(Pc)(CN)2]2 (-32%) and Ph4P[FeIII(tbp)(CN)2]2 (-13%) analogues (Pc = phthalocyanine and tbp = tetrabenzoporphyrin). This small negative magnetoresistance effect of Ph4P[FeIII(Pc)(CN)2]2 could be ascribed to the weak intermolecular antiferromagnetic interaction between its d spins. Hence, this study showed that constructing a molecular design for strengthening the intermolecular antiferromagnetic interaction is key to enhancing the negative magnetoresistance effect.

Lanthanide-based bis-(3,5-dicarboxy-phenyl)terephthalamide metal–organic frameworks: slow relaxation of magnetization and detection of trace Fe2+ and Fe3+

{[Dy2(BDPT)1.5(DMF)4]·H2O}n (1) and [Sm2(BDPT)1.5(DMF)4]n (2) were prepared with highly sensitive fluorescent detection of trace Fe2+ and Fe3+. 1 exhibits weak antiferromagnetic interactions with signature of SMM behavior.

Facile and environmentally friendly one-step synthesis of hexanuclear Cu(II)–Ni(II) and Cu(II)–Co(II) clusters and their binding interactions with bovine serum albumin

The novel hexanuclear {K6[Cu4Co2(μ3-OH)4(μ4-O)(OAc)8][Cu(OAc)4](OH)2}·3H2O (1) and {K6[Cu4Ni2(μ3-OH)4(μ4-O)(OAc)8][Cu(OAc)4](OH)2}·3H2O (2) clusters have been prepared. The clusters were synthesized by the self-assembly of Cu(OAc)2 and M(OAc)2 (M ​= ​Co, Ni) in aqueous solution without any additional other organic ligands. The two clusters were well-characterized with single-crystal X-ray diffraction, FT-IR spectra and elemental analyses. Crystallographic studies revealed that the molecular core type was M6(μ3-OH)4(μ4-O) in both 1 and 2. Solid-state DC magnetization indicated that 2 exhibited strong Ni–O–Ni associated antiferromagnetic interaction, while 1 displayed merely weak antiferromagnetic interaction. The protein binding affinity of two clusters was tested with bovine serum albumin (BSA). Both two clusters showed good affinity with BSA, with a binding constant (Kb) of 4.97 ​× ​104 ​M−1and 2.14 ​× ​104 ​M−1, respectively. Cytotoxic activity was performed by MTT assay. It was observed that the complex exhibited low toxicity against the SH-SY5Y and A549 cancer cells.

A one-dimensional chiral gadolinium complex based on a tartaric acid derivative: crystal structure, thermal behavior and magnetic properties

A new chiral one-dimensional gadolinium coordination polymer [Gd(HDTTA)3(CH3OH)3]n (1) (D-H2DTTA = (+)-Di-p-toluoyl-D-tartaric acid) was synthesized at room temperature, and fully structurally characterized by Infrared (IR), elemental analysis (EA), single-crystal and powder X-ray diffraction (PXRD). The structure analysis shows that complex 1 belongs to the trigonal system with R3 space group and displays an infinite chain structure along the c axis. In 1, each Gd3+ cation is in the tri-capped trigonal prism geometry, and neighboring Gd3+ cations are connected by three partly deprotonated HDTTA− ligands with the Gd···Gd distance of 7.686(1) Å. The circular dichroism (CD) spectrum demonstrates the chirality of the complex. Magnetic studies reveal that complex 1 displays weak antiferromagnetic interactions between Gd3+ cations and it exhibits a small magnetic entropy change (−ΔS m = 7.26 J kg−1 K−1 with ΔH = 7 T and T = 2.5 K) because of long Gd···Gd distance and relatively low magnetic density.

STRUCTURE OF A Pd–ORGANIC PARAMAGNETIC

By the interaction of 2-bromo-4,4,5,5-tetramethyl-2-imidazoline-3-oxide-1-oxyl (NN–Br) with tetrakis(triphenylphosphine)palladium(0) a new paramagnetic palladium-organic compound [Pd(NN)(PPh3)2Br] is synthesized. The crystal structure of its tetrahydrofuran solvate is determined by X-ray diffraction. The obtained data allow us to expect that the effective Pd–C bond eclipsing by phenyl rings deactivates the compound in a cross-coupling reaction with aryl halides and provides its high kinetic stability under normal conditions. Magnetochemical studies show the presence of weak antiferromagnetic exchange interactions between spins of paramagnetic [Pd(NN)(PPh3)2Br].