Weak Antiferromagnetic Coupling Research Articles

Mono-, di-, and trinuclear phosphonate oxygen-bridged copper(II) complexes: syntheses, structures, and properties

Reactions of copper salts, zoledronic acid, and 2,2′-bipyridine/1,10-phenanthroline in aqueous ethanolic solutions afforded four phosphonate oxygen-bridged copper complexes, Cu(bipy)(H4zdn)(HSO4) (1), [Cu2(bipy)2(H2zdn)(H2O)(Cl)]·4H2O (2), [Cu2(phen)2(H2zdn)(H2O)(Cl)]·2.5H2O (3), and [Cu3(bipy)3(H4zdn)(H2zdn)(SO4)]·5H2O (4) (H5zdn = zoledronic acid, bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline). The copper centers of 1–4 have square pyramidal coordination geometries. The Cu(II) ions are coordinated to bipy/phen, zoledronate, and HSO4−/Cl− forming mononuclear units for 1, dinuclear for 2 and 3, and trinuclear for 4. These building units are further extended into 3-D supramolecular networks via multiple hydrogen bond interactions. Temperature-dependent magnetic properties of 2 and 4 suggest weak antiferromagnetic coupling (J = −4.53(8) cm−1 for 2, J = −1.69(4) cm−1 for 4). The antitumor activity of 2 was evaluated against the human lung cancer cell line and indicates effective time- and dose-dependent cytotoxic effects.

Counterion-Induced Variations in the Dimensionality and Topology of Uranyl Pimelate Complexes

The structure-directing effect of counterions with different shapes and charges has been investigated in the case of the complexes formed by uranyl ions with pimelic (heptanedioic) acid (H2C7) under solvo-hydrothermal conditions. Following the previously reported isolation of one-dimensional (1D) chains with the counterions [Fe(bipy)3]2+ and [Cu(phen)2]+, the complex [Ni(Me4phen)3]2[(UO2)4(C7)3(NO3)6]·CH3CN (1), with a bulkier cation, was synthesized and shown to consist of molecular anionic tetranuclear uranyl species, the presence of coordinated nitrate ions preventing polymerization. 1D zigzag chains are formed in [Ag(bipy)2]2[UO2(C7)(NO3)]2 (2), in which the cations, assembled into dimers through argentophilic interactions, are organized in columns through π-stacking interactions. The heterometallic complex [UO2Mn(C7)2(phen)2] (3) is formed in the presence of manganese(II) cations, and it crystallizes as a two-dimensional (2D) assembly in which manganese dimers display weak antiferromagnetic coupling ...

Two Six-Connected MOFs with Distinct Architecture: Synthesis, Structure, Adsorption, and Magnetic Properties.

By assembling CoII ions and a combination of 5-(4-pyridyl)tetrazole (4-ptz) and formate ions, two distinct metal-organic frameworks, [Co3 (4-ptz)5 (HCOO)(H2 O)2 ] and [Co3 (4-ptz)4 (dmf)2 (HCOO)2 ] (dmf=N,N'-dimethylformamide), were synthesized. They were both characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. Structural analyses revealed that by slightly modulating the coordination environment of the trinuclear cobalt cluster, two complexes were formed featuring unusual six-connected nets reminiscent of a pyrazole-type linear trinuclear cobalt cluster as compared with the classic eight-connected bcu topology. In addition, [Co3 (4-ptz)5 (HCOO)(H2 O)2 ] interacted strongly with CO2 , with an adsorption enthalpy of 29.2 kJ mol-1 , and in a selectivity study, the uptake ratios of CO2 /N2 (from a 15:85 mixture) and CO2 /CH4 (50:50 mixture) were 77.6 and 37.7, respectively. Magnetic studies on both complexes revealed weak antiferromagnetic coupling between the CoII ions.

Synthesis, Crystal Structure and Magnetic Properties of Heteropolynuclear ReIVMII Complexes Based on the Robust [ReCl5(pyzCOO)]2– Unit (pyzCOO = 2‐pyrazinecarboxylate)

AbstractThe syntheses, crystal structures and magnetic properties of four rhenium(IV) compounds of formulae NBu4[ReCl5(pyzCOOH)]·H2O (1), [ReCl5(µ‐pyzCOO)M(dmphen)2]·2CH3CN [M = Ni (2) and Co (3)] and {[ReCl5(µ3‐pyzCOO)]2Mn2(dmphen)3}n (4) (NBu4 = tetra‐n‐butylammonium cation, pyzCOOH = 2‐pyrazinecarboxylic acid, dmphen = 2,9‐dimethyl‐1,10‐phenanthroline) are reported herein. Compound 1 was obtained by the reaction of NBu4[ReCl5(dmf)] (dmf = dimethylformamide) with pyzCOOH in acetone, whereas the other complexes were obtained by the reaction of 1 with M(ClO4)2·6H2O [M = Ni (2), Co (3), Mn (4)] and dmphen in acetonitrile. Complex 1 is a mononuclear compound, 2 and 3 are neutral heterodinuclear complexes and 4 is a neutral chain in which each pyzCOO– bridges one ReIV and two MnII in a very unusual µ3‐binding mode. Compounds 2 and 3 behave as magnetically isolated species with intramolecular ferromagnetic coupling between ReIV and NiII or ReIV and CoII ions, respectively. In turn, weak antiferromagnetic coupling between the MnII ions through anti‐syn‐carboxylate bridges together with weak ferromagnetism below 3.1 K due to small spin canting is observed in 4.

Magnetic Properties of a Single‐Molecule Lanthanide–Transition‐Metal Compound Containing 52 Gadolinium and 56 Nickel Atoms

AbstractMonodisperse metal clusters provide a unique platform for investigating magnetic exchange within molecular magnets. Herein, the core–shell structure of the monodisperse molecule magnet of [Gd52Ni56(IDA)48(OH)154(H2O)38]@SiO2 (1 a@SiO2) was prepared by encapsulating one high‐nuclearity lanthanide–transition‐metal compound of [Gd52Ni56(IDA)48(OH)154(H2O)38]⋅(NO3)18⋅164 H2O (1) (IDA=iminodiacetate) into one silica nanosphere through a facile one‐pot microemulsion method. 1 a@SiO2 was characterized using transmission electron microscopy, N2 adsorption–desorption isotherms, and inductively coupled plasma‐atomic emission spectrometry. Magnetic investigation of 1 and 1 a revealed J1=0.25 cm−1, J2=−0.060 cm−1, J3=−0.22 cm−1, J4=−8.63 cm−1, g=1.95, and z J=−2.0×10−3 cm−1 for 1, and J1=0.26 cm−1, J2=−0.065 cm−1, J3=−0.23 cm−1, J4=−8.40 cm−1 g=1.99, and z J=0.000 cm−1 for 1 a@SiO2. The z J=0 in 1 a@SiO2 suggests that weak antiferromagnetic coupling between the compounds is shielded by silica nanospheres.

Magnetic Properties of a Single-Molecule Lanthanide-Transition-Metal Compound Containing 52 Gadolinium and 56 Nickel Atoms.

Monodisperse metal clusters provide a unique platform for investigating magnetic exchange within molecular magnets. Herein, the core-shell structure of the monodisperse molecule magnet of [Gd52 Ni56 (IDA)48 (OH)154 (H2 O)38 ]@SiO2 (1 a@SiO2 ) was prepared by encapsulating one high-nuclearity lanthanide-transition-metal compound of [Gd52 Ni56 (IDA)48 (OH)154 (H2 O)38 ]⋅(NO3 )18 ⋅164 H2 O (1) (IDA=iminodiacetate) into one silica nanosphere through a facile one-pot microemulsion method. 1 a@SiO2 was characterized using transmission electron microscopy, N2 adsorption-desorption isotherms, and inductively coupled plasma-atomic emission spectrometry. Magnetic investigation of 1 and 1 a revealed J1 =0.25 cm(-1) , J2 =-0.060 cm(-1) , J3 =-0.22 cm(-1) , J4 =-8.63 cm(-1) , g=1.95, and z J=-2.0×10(-3) cm(-1) for 1, and J1 =0.26 cm(-1) , J2 =-0.065 cm(-1) , J3 =-0.23 cm(-1) , J4 =-8.40 cm(-1) g=1.99, and z J=0.000 cm(-1) for 1 a@SiO2 . The z J=0 in 1 a@SiO2 suggests that weak antiferromagnetic coupling between the compounds is shielded by silica nanospheres.

Magnetization Process of Spin-1/2 Heisenberg Antiferromagnets on a Layered Triangular Lattice

We study the magnetization process of the spin-1/2 antiferromagnetic Heisenberg model on a layered triangular lattice by means of a numerical cluster mean-field method with a scaling scheme (CMF+S). It has been known that antiferromagnetic spins on a two-dimensional (2D) triangular lattice with quantum fluctuations exhibit a one-third magnetization plateau in the magnetization curve under magnetic field. We demonstrate that the CMF+S quantitatively reproduces the magnetization curve including the stabilization of the plateau. {We also discuss the effects of a finite interlayer coupling, which is unavoidable in real quasi-2D materials. It has been recently argued for a model of the layered-triangular-lattice compound Ba3CoSb2O9 that such interlayer coupling can induce an additional first-order transition at a strong field. We present the detailed CMF+S results for the magnetization and susceptibility curves of the fundamental Heisenberg Hamiltonian in the presence of magnetic field and weak antiferromagnetic interlayer coupling. The extra first-order transition appears as a quite small jump in the magnetization curve and a divergence in the susceptibility at a strong magnetic field ~ 0.712 of the saturation field.

Synthesis, Crystal Structure, Thermal Analysis, Spectroscopic, and Magnetic properties of a Novel Organic Cation Tetrachlorocobaltate(II)

The preparation and structural characterization of a new complex (C11H18N2O)2[CoCl4]2.H2O (I) are described. The crystal structure determination shows that the title compound crystallizes in the Pccn space group of the orthorhombic system. The unit cell dimensions are as follows: a = 29.090 A, b = 9.774 A, and c = 11.751 A, with Z = 4. The crystal structure of this salt was solved by Patterson methods and refined by full-matrix least squares on F 2 to final values of R = 0.0333 and wR = 0.0771. The tetrahedral (CoCl4)2− anions are connected to the 1-(2-methoxyphenyl)piperazinium cations by hydrogen bonding (N–H ⋯Cl and O–H ⋯Cl). The crystals were characterized by employing several techniques such as single-crystal X-ray diffraction, thermo differential and gravimetric analyses, IR, RMN and UV-vis spectra, and fluorescence properties. Moreover, magnetic susceptibility measurements indicate that the compound exhibits weak antiferromagnetic coupling interaction.

Spontaneous resolution of heterometallic complex: cis-[Co(NH3)4(H2O)2][Fe(ox)3]·2H2O – A rare example for labile iron(III) complex

The new conglomerate forming compound of the formula cis-[Co(NH3)4(H2O)2][Fe(ox)3]·2H2O (1) (ox=C2O42−) was synthesized and structurally, spectroscopically and magnetically characterized revealing weak antiferromagnetic couplings. Two forms of (1) crystallizing in hexagonal enantiomorphic space groups, P6522 and P6122, were identified proving that spontaneous resolution of the racemic mixture occurred at the crystallization stage, because chiral (1a) and (1b), respectively, were obtained from the same synthesis using racemic K3[Fe(ox)3]·3H2O substrate. It is rare example of conglomerate formation with labile Fe(III) ion as a coordination center. In packing along z axis for (1a) and (1b) structures we observe pattern with iron and cobalt complexes as well as water molecules arranged in separated helices, left-handed for (1a) and right-handed for (1b). Analysis of the intermolecular contacts formed by the “false block” with inverted chirality placed in the homochiral network revealed steric hindrance as well as disruption of approximately 50% of hydrogen bonds inside a helix and between adjacent helices. This analysis was supported by calculations performed using gaussian-03 run with DFT B3LYP potential using 6–31+G(d,p) basis. They revealed significantly more stable structure for the true block due to disruption of several hydrogen bonds and steric hindrance introduced by the false block. Hence, the helices imposed by chiral [Fe(ox)3]3− blocks are a template for supramolecular structure, which reveals achiral water molecules and Co(III) moieties forming helices of the same handedness as iron blocks. These Fe(III) moieties are trapped inside tightly packed crystal network, which is maintained by the robust hydrogen bond network. In this structure Co(III) blocks transmit interactions between adjacent helices. Analysis of intermolecular interactions network allows also for deeper insight into a nature of light- and/or time-catalyzed degradation as well as spontaneous resolution processes.

Synthesis, Crystal Structures, and Magnetic Properties of Two [Cu(cyclm)]2+-Based One-Dimensional Chain Complexes

With polyimine macrocyclic compound [Cu(cyclm)]2+ as assembly segment, two 1D coordination polymers, {[Cu(cyclm)Br][Ru(acac)2(CN)2]}n∙nCH3OH (1) and {[Cu(cyclm)Br]ClO4}n∙nCH3CN∙nH2O (2), have been synthesized and structurally characterized. Single-crystal X-ray diffraction analysis shows their 1D cationic structure comprised by the repeating unit [Cu(cyclm)Br]+ with [Ru(acac)2(CN)2]− or ClO4− as balance anion (cyclm = 1,4,8,11-tetraazacyclotetradecane, acac = acetylaceto). Investigation of the magnetic properties of these two complexes reveals the weak antiferromagnetic magnetic coupling between the neighboring Cu(II) bridged by bromide ions. A best fit to the magnetic susceptibilities of complexes 1 and 2 leads to the magnetic coupling constants J = 1.02(2) (1) and 1.05(2) cm−1 (2), respectively.

Syntheses, structural, spectroscopic and magnetic properties of polynuclear Fe(III) complexes containing N and O donor ligands

Syntheses, X-ray structural and spectroscopic properties are reported for [{Fe(L)2}3Fe] (1), [Fe2(L)2(ClCH2COO)2(H2O)] (2) and [Fe(L)(HL)]2 (3) [H2L=a tridentate ONO-donor ligand N-(2-hydroxyphenyl)salicylidenimine]. For (2) and (3), variable temperature magnetic susceptibilities have been measured and modeled. Both are antiferromagnetic overall. Compound 1 has a tetranuclear Fe4O6 core with Fe(III) species at the vertices of a triangle and the fourth Fe(III) at the center of the triangle. The central Fe(III) is surrounded by six phenoxo bridges that connect it to the three peripheral Fe(III) centres. In complex 2, the two six-coordinate Fe(III) centers are bridged by a chloroacetate and two phenoxy oxygens. The remaining three coordination sites on each iron are occupied by a terminal phenoxy oxygen, an imino nitrogen and, in one case, by a water oxygen while in the other by a terminal chloroacetate oxygen. Comparison of 2 with compounds of similar core structure reveals transition between antiferromagnetic and ferromagnetic coupling occurs at a bridgehead angle between ∼97° and ∼102°. The asymmetric unit of compound 3 consists of two symmetry-independent mononuclear species (Z′=2) joined by two statistically equivalent short (2.429(2) and 2.432(2)Å) O⋯H⋯O bridges, each involving two phenolic oxygens and a strongly bound H atom. Unprecedented weak antiferromagnetic coupling between the two high spin Fe(III) species via these very strong hydrogen bonds was detected.

Alkaline Ion-Modulated Solid-State Supramolecular Organization in Mixed Organic/Metallorganic Compounds Based on 1,1′-Ethylenebis(4-aminopyridinium) Cations and Bis(oxamate)cuprate(II) Anions

Three new coordination compounds of formula (edap)2[Cu(opba)]2·4H2O (1), (edap)[{Na2(H2O)4}{Cu2(opba)2}]·2H2O (2), and (edap)[{K2(H2O)2}{Cu2(opba)2}]·3H2O (3) (edap = 1,1′-ethylenebis(4-aminopyridinium) and opba = 1,2-phenylenebis(oxamate)) were synthesized through the metathesis reaction involving A2[Cu(opba)] (A = Li+, Na+, and K+) and (edap)Cl2·2H2O. Crystal structures of 1–3 and edap(IO3)2·4H2O compound were elucidated by single crystal X-ray diffraction. Compounds 1–3 are built up from dinuclear copper(II) entities, {[Cu(opba)]2}4– with an asymmetric bis(monatomic oxygen) bridge resulting from the parallel “out-of-plane” disposition of the planar mononuclear [Cu(opba)]2–. They possess distinct supramolecular arrangements of varying dimensionality (nD with n = 0 (1), 1 (2), and 2 (3)) in the solid state depending on the nature of the coordinated alkaline ion present alongside edap2+ counterions. While the {[Cu(opba)]2}4– building blocks are well-isolated in 1, they form either double chains or corrugated layers due to the coordination of the Na+ or K+ ions in 2 and 3, respectively. Magnetic properties of 1–3 show a very weak antiferromagnetic coupling between the CuII ions through a double monatomic (μ-O) bridge (−J = 1.63(9) (1), 2.29(2) (2), and 1.65(3) cm–1 (3)), the Hamiltonian being defined as H = −(S1·S2) + g βH(S1 + S2).

Nickel adipate coordination polymers with isomeric dipyridylamide ligands: topological disorder and divergent magnetic properties

Hydrothermal reaction of nickel nitrate, adipic acid, and a dipyridylamide ligand produced two coordination polymers which were structurally characterized by single-crystal X-ray diffraction. {[Ni2(adipate)2(3-pna)2(H2O)]·H2O}n (1, 3-pna = 3-pyridylnicotinamide) possesses carboxylate bridged {Ni(μ2-H2O)(OCO)2} dimeric units connected into (6,3) graphitic 2D layer motifs. Use of the isomeric 3-pyridylisonicotinamide (3-pina) afforded {[Ni2(adipate)2(3-pina)2(H2O)]·2H2O}n (2), which manifested similar {Ni(μ2-H2O)(OCO)2} dimeric units. Crystallographic disorder within the adipate ligands in 2 produced a 3D coordination polymer net that is a hybrid of a non-interpenetrated 3D 6-connected primitive cubic α-Po 41263pcu net and 2D 7-connected slab motifs with a pillared (3,6) triangular net 3641253 topology. Magnetic analysis for 1 revealed weak antiferromagnetic coupling (J = −0.36(1) cm−1 with g = 2.077(1)), while 2 exhibited weak ferromagnetic coupling (J = +0.51(2) cm−1 with g = 2.034(7)).

Tetranuclear manganese(II) complexes of hydrazone and carbohydrazone ligands: Synthesis, crystal structures, magnetic properties, Hirshfeld surface analysis and DFT calculations

The complexes [Mn4(L1)4(N3)4] (1), [Mn4(L2)4(μ-N3)2(N3)2(OCH3)2] (2) and [Mn4(μ-L3)4(NCS)4]·6CH3OH (3) [L1=N-1-(pyridin-2-yl)ethylidenepicolinohydrazonate, L2=N-phenyl(pyridin-2-yl)methylenepicolino hydrazonate, and L3=((phenyl(pyridin-2-yl)methylene)hydrazinyl)((Z)-2-(phenyl(pyridin-2-yl)methylene)hydrazinyl)methanolate] have been synthesized, and their structures characterized. The structures of 1 and 3 can be described as tetranuclear and are formed from four Mn(II) ions bridged by four ligands. Complex 2 exhibits a centrosymmetric tetranuclear structure with two types of Mn(II) centers with double end-on (EO) azido bridges. All the complexes have similar magnetic behavior and exhibit weak intramolecular antiferromagnetic coupling, which is consistent with the oxygen-bridged square structures with large Mn–O–Mn bridge angles. Theoretically obtained J values of −1.7cm−1 (for 1), −0.7cm−1 (for 2) and −3.3cm−1 (for 3) corroborate well the experimental results. Moreover, a Hirshfeld surface (HS) analysis was employed to gain additional insight into interactions responsible for packing of complexes 1–3 (with dnorm and shape-index functions). Quantitative examination of 2D fingerprint plots revealed, amongst others, the dominating participation of H⋯H and H⋯C interactions in the molecular packing.

Synthesis, structure and magnetic properties of a binuclear copper(II) complex constructed by a new coordination mode of the tetrachlorophthalate ligand

Abstract A binuclear complex [Cu2(tcpa)2(bipy)2(H2O)3] (1) (H4tcpa = tetrachlorophthalic acid, bipy = 2,2′-bipyridine) has been synthesized and structurally characterized. Two independent CuII centers Cu1 and Cu2 are both five-coordinated in distorted square pyramids. The tetrachlorophthalate (tcpa2–) anions show a new coordination mode: one is monodentate at Cu1, and the other displays a bridging μ 2-O,O″ fashion linking Cu1 and Cu2, thus forming the binuclear structure of 1. Variable-temperature magnetic susceptibility data show weak antiferromagnetic coupling between the two CuII ions.

Cyanide-bridged bi- and trinuclear heterobimetallic Fe(III)–Mn(III) complexes: Synthesis, crystal structures and magnetic properties

By employing trans-dicyano or pentacyanometalate as building block and using a bicompartimental Schiffbase based manganese(III) compound as assemble segment, two new cyanide-bridged heterometallic Fe(III)–Mn(III) complexes {[Mn(L)(H2O)][Febpb(CN)2]}·2CH3OH (1) and {[Mn(L)(H2O)]2··[Fe(CN)5NO]} (2) (bpb2– = 1,2-bis(pyridine-2-carboxamido)benzenate, L = N,N'-ethylene-bis(3-ethoxysalicylideneiminate) have been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. Single X-ray diffraction analysis reveals binuclear FeMn and trinuclear FeMn2 structure, respectively, in which the cyanide precursor acts as mono- or bidentate ligand to connect the Mn(III) Schiff-base unit(s). Furthermore, these two complexes are self-complementary through coordinated aqua ligands from one complex and the free O4 compartments from the neighboring complex, giving dimeric and 1D single chain supramolecular structure. Investigation of the magnetic susceptibility of 1 reveals weak antiferromagnetic coupling between the adjacent Mn(III) ions. Based on the binuclear FeMn model, best fit of the magnetic susceptibilities of 1 leads to the magnetic coupling constants J =–1.37 cm–1 and zJ′ =–0.72 cm–1 (1).

Syntheses, crystal structures, and magnetic properties of two 1D manganese(II) complexes bearing fluorenylcarboxylate ligands

1D manganese carboxylates [Mn(mfa)2(H2O)]n (1) and {[Mn3(mfp)6(CH3OH)2]·2CH3OH}n (2) (Hmfa=2-(9-methyl-9H-fluoren-9-yl)acetic acid, Hmfp=3-(9-methyl-9H-fluoren-9-yl)propanoic acid) were synthesized by reactions of Mn(ClO4)2·6H2O and the corresponding carboxylate. In compound 1, the Mn(II) ions are bridged by two carboxylate groups in μ2-η1,η1 and μ2-η2,η1 bridging modes into one uniform chain. Compound 2 has a distinctive chainlike structure contrast to compound 1, that are constructed alternatively from mononuclear Mn(II) and dinuclear [Mn2(mfp)2(CH3OH)2] units by two μ2-η1,η1-carboxylates and one O atom from the third carboxylate ligand. Magnetic susceptibility measurements revealed a weak antiferromagnetic coupling for both complexes. The magnetic data were fitted by using uniform chain and –AF1–AF1–AF2– antiferromagnetic chain models for 1 and 2, respectively.

Magnetic and Spectroscopic Study on a New Asymmetric Mixed‐valence Mn2(II,III) Coordination Compound

Abstract A new dinuclear mixed‐valence compound [MnIIMnIII(bttpnol)(O2C–C6H4–NO2)2]ClO4 was synthesized by using the asymmetric heptadentate ligand N‐(2‐hydroxybenzyl)‐N,N′,N′‐tris(2‐pyridylmethyl)‐1,3‐diaminopropan‐2‐ol (H2btppnol). One central manganese atom assumes N3O3 and the other N2O4 coordination sphere. Both manganese ions are bridged by the alkoxy‐group of the dinucleating ligand and two bidentate carboxylate groups of the nitrobenzoate ligands. The structural data show clearly that MnIII prefers the more oxygen rich donor set. Cyclic voltammetry measurements reveal that the mixed‐valence state Mn2(II,III) could be reduced to Mn2(II,II) at E1/2(1) = –0.53 V and oxidized to Mn2(III,III) at E1/2(2) = 0.52 V (vs. ferrocene). Measurements of the magnetic susceptibility reveal a weak antiferromagnetic coupling with J = –8.5 cm–1. The mixed valence state was additionally confirmed by EPR spectroscopy showing the hyperfine signal of the S = 1/2 state of Mn2(II,III).

Sulfadiazine/dimethylsulfadiazine transition metal complexes: Synthesis, crystal structures and magnetic properties

Sulfadiazine (Hsulf) and dimethylsulfadiazine (Hdmsulf) were used to assemble divalent transition metal complexes (Cu, Ni or Co). Solvated complexes 1–4, dinuclear 1 (Cu2), tetranuclear 2 (Ni4) and 3 (Co4), and two-dimensional polymeric 4, were synthesized by controlling the metal ions, ligands and solvents. For complex 1, two Cu(II) ions are bridged by four NCN groups of four sulf− ligands, while for complex 2, four Ni(II) ions are alternatively bridged by the pyrimidine rings of four sulfadiazine ligands, forming a neutral square Ni4 molecule. In complex 3, four Co(II) ions are bridged by four μ3-OMe− groups, yielding a Co4O4 cubane. Complex 4 possesses a 2D grid structure with the Co(II) ions bridged by the remote amino groups of the ligand dmsulf−. Magnetic susceptibility measurements show that the desolvated complex (1d) exhibits antiferromagnetic coupling between adjacent Cu(II) ions with the 2J value of −90.0cm−1, and the pyrimidine rings transmit weak antiferromagnetic coupling in complex 2. Complex 3·8H2O shows ferromagnetic coupling via the methoxido bridges with the bridging CoOCo bond angles of 96–99°. Complex 4 displays a magnetic property for mononuclear cobalt(II) complexes due to the remote separation of Co(II) ions.

Structural characterization of μ1,2- and μ1,3-bridged-squarato 1D metal(II) coordination polymers

Three bridged squarato 1-D polymeric M(II) complexes were synthesized and structurally characterized: {[Cu2(LBDPA)(μ1,2-C4O4)(H2O)](ClO4)2·2H2O}n (1), {[Mn(DPA)(μ1,2-C4O4)(H2O)]·2H2O}n (2) and {[Zn(DPA)(μ1,3-C4O4)(H2O)]·2H2O}n (3) where LBDPA=2,6-bis[bis(2-pyridylmethyl)aminomethyl]pyridine (LBDPA), DPA=bis(2-pyridylmethyl)amine, C4O42−=squarate dianion. Also, attempts were made to solve the X-ray structure of [Cd(Mepea)(μ1,2-C4O4)(H2O)]n (4) (Mepea=N-methyl-(2-pyridylmethyl)-(2-(2-pyridyl)ethyl)amine). The C4O42− dianions are bridging the M2+ centers via bis(monodentate) μ1,2-(cis) or μ1,3-(trans) bonding modes. Complex 1 reveals very weak antiferromagnetic coupling between the Cu(II) ions.