Crystal Structure and Luminescent Property of a Coordination Complex Constructed with Pyrazine and 1,4-Phenylenediacetic Acid

A new coordination complex [Cd(pda)(pyz)(H2O)2]n(1, H2 pda = 1,4-phenylenediacetic acid, pyz = pyrazine) have been synthesized and structurally characterized. Crystal data for the title complex are as follows: orthorhombic system, space group Ccmb with a = 11.5245(3) b = 19.5069(5) c = 11.4231(3) A, V = 2568.00(12) A3, Mr = 188.31, Z = 16, F(000) = 1480, Dc = 1.948 g/cm3, μ(Mo Kα) = 1.725 mm-1, R = 0.0195 and w R = 0.0462 for 1357 observed reflections with I 2σ(I). In the title complex, the central Cd(II) ion is located in a distorted octahedral coordination environment. Two Cd(II) ions are bridged by two pda2- ligands and one pyz ligand to form a bi-loop structure. Luminescent property of the complex has also been studied.     

Synthesis and Crystal Structure of a Novel Double Ladder-like Cadmium Coordination Polymer Constructed by Isophthalate and Imidazole

A novel double ladder-like cadmium coordination polymer with isophthalate as bridging ligands and imidazole as non-chelating capping ligands was obtained by a hydrothermal reaction. The crystal is of triclinic, space group P1 with a = 10.266（2）, b = 11.573（2）, c = 12.651（3） A, α = 89.95（3）, β= 74.64（3）,γ = 68.54（3）°, C50H44Cd4N12O18, Mr = 1550.57, V= 1341.1（5）A3, Dc = 1.920 g/cm3, F（000） = 764, p = 1.651 cm-1 and Z = 1. The final refinement gave R = 0.0342 and wR = 0.0738 for 5925 observed reflections with I 〉 2σ（I）. The crystal structure involves two different ladder-like chains, which are further connected to form a ladder-like double chain architecture via hydrogen bonding interactions, extending along the b axis. The weak interactions including hydrogen bonds and π-π staking interactions contribute to the alignment of the complex in the crystalline state.     

A Silver Complex of 6,7-Dicyanodipyridoquinoxaline： π-Stacking Interactions and Luminescence

The reaction of 6,7-dicyanodipyridoquinoxaline （DICNQ） with AgNO3 in a 1：1 molar ratio by solution method gave a new complex [Ag（DICNQ）2]NO3 1. Single-crystal X-ray diffraction analysis reveals that the complex crystallizes in the space group Ibca of orthorhombic system with eight formula units in a cell. Crystal data for 1： a = 15.7055（17）, b = 18.411（2）, c = 20.680（2）A, V = 5979.7（11）A3, Z = 8, C32Hl2AgN13O3, Mr = 734.42, Dc = 1.632 g/cm3, μ= 0.734 mm-1, F（000） = 2928, S = 1.023 and T= 293（2） K. The final R = 0.0659 and wR = 0.1927 for 2118 observed reflections with I 〉 2σ（I）, and R = 0.0801 and wR = 0.2196 for all data. The complex builds up a packing structure by π-π stacking interactions and shows a luminescent feature.     

Synthesis,Structure and Norbornene Polymerization Activity of a Novel Palladium（ II ） Complex with N,N＇-bis（2-benzoyl-3-oxobutane）-trans-l,2- diaminocyclohexane Ligand

The title complex N,N＇-bis（2-benzoyl-3-oxobutane）-trans-l,2-diaminocyclo- hexane-palladium （C28H28N2PdO4） has been synthesized by the reaction of N,N＇-bis（2- benzoyl-3-oxobutane）-trans-l,2-diamino-cyclohexane with PdCI2, and characterized by ele- mental analysis, IR spectrum, WAXD and TG. The spatial structures of the complex have been confirmed by single-crystal X-ray diffraction analysis. The compound crystallizes in the monoclinic system, space group C2/c with a = 29.763（6）, b = 10.320（2）, c = 18.921（4） A, fl = 102.75（3）°, V = 5668（2） A3, C28H28N2PdO4·CH3OH, Mr = 594.97, Z = 8, Dc = 1.394 g/cm3, μ（MoKa） = 0.694 mm-1, F（000） = 2448, T= 293（2） K, R = 0.0572 and wR = 0.1347 （I〉 2σ（I））. The compound was investigated for the catalytic behavior towards norbornene （NB） vinyl addition polymerization. And the palladium complex showed excellent catalytic activity up to 9.97x 106g of PNB （mol of Pd）-1 h-1 with high monomer conversion using methylaluminoxane （MAO） as a cocatalyst.     

Crystal Structure,Electrochemical and Fluorescent Properties of a New Cadmium（II） Complex [Cd（C12H6O4N2）（Phen）2（H2O）]·3H2O

A new Cd（II） complex [Cd（C12H6OaN2）（Phen）ffH2O）]＇3H2O with 2,2＂-bipyridine- 3,3＂-dicarboxylic acid as a ligand has been synthesized. Crystal data for the title complex are as follows： monoclinic, space group P2dn, a = 12.8458（5）, b = 17.9131（7）, c = 15.2960（6） A, β = 111.7430（10）°, V = 3269.3（2） A3, Dc = 1.581 g/cm3, Z = 4,/a（MoKa） = 0.731 mm-1, F（000） = 1580, the R = 0.0244 and wR = 0.0605. In the title complex, the central Cd（ll） ion is located in a distorted octahedral coordination environment. The electrochemical and fluorescent properties of the title complex were studied. The results show that the electron transfer of the title complex is irreversible in the electrode reaction and it has a broad emission peak in the range of 470-508 nm with the excitation wavelength of 488 nm.     

A Novel Complex of Na（I）-Nitronyl Nitroxide [Na（NIT- 1＇-MeBzIm）3]ClO4： Synthesis and Crystal Structure

A novel complex [Na（NIT-1＇-MeBzIm）3]ClO4 （NIT-1＇-MeBzIm = 2-{2＇-[（1＇- methyl）benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide） has been prepared and structurally characterized by elemental analysis, IR spectra and X-ray diffraction methods. The title complex crystallizes in trigonal, space group P3 and Z = 2. Crystal data： C45H57ClN12NaO10, Mr = 984.47, a = 13.9411（8）, b = 13.9411（8）, c = 14.8622（16） A, γ= 120°, V= 2501.5（3） A^3, Dc = 1.307 g/cm^3, μ（MoKα） = 0.152 mm^-1, F（000） = 1038, R = 0.0637 and wR = 0.1813 for 1957 observed reflections with I 〉 2σ（I）. X-ray analysis reveals that the Na（I） ion is six-coordinated with three NIT-1＇-MeBzlm radicals. As we know, three radicals coordinating to the Na（I） ion in the main group by a chelate way is the first example. The Na（I） ion resides in a distorted octahedron with a facial configuration. Meanwhile, the intermolecular weak interactions result in a 2-D double layer conformation where the uncoordinated perchlorate anions are inserted in the packing space and take part in the H-bond interactions, and each complex is connected with six neighboring complexes and three perchlorate anions.     

Single-crystal Structure of ScAlMgO4

Crystals of scandium magnesium aluminate, ScAlMgO4, were grown from the melt prepared from stoichiometric quantities of Sc2O3, Al2O3 and MgO. Single-crystal X-ray diffraction indicates that ScAlMgO4 crystallizes in the space group R3 m with a = b = 3.2506（9） A, c = 25.152（8）A, V= 230.16（11）A^3, Z= 3, F（000） = 234,μ = 2.424 cm^-1, the final R = 0.0381 and wR = 0.1061 for 1874 observed reflections with I 〉 2σ（I）. In ScAlMgO4, all Sc atoms are coordinated octahedrally, whereas AI or Mg atoms are forming a tetrahedron, or in a triangular bipyramid if one distant O atom is included. The structure of ScAlMgO4 is characterized by { [AlMgO4]^3-}∞^2 layers parallel to the ab plane, and they are further connected into a 3-dimen-sional framework by Sc atoms via O（1） atoms between the layers.     

Two-dimensional Supramolecular Structure of a Mercury（Ⅱ） Iodide Complex with Organosulfide

A mercury（Ⅱ） iodide complex with organosulfide [Hg（pymt）（pymtH）I] 1 （pymt = the anion of pyrimidine-2-thiolate） has been synthesized by slow evaporation of the solution at room temperature and structurally characterized by single-crystal X-ray diffraction. Basic ideas and data collected are given. X-ray diffraction analysis reveals that complex 1 is mononuclear. Crystallographic data： C8H7HgIN4S2, Mr = 550.79, monoclinic system, space group P21/c, a = 11.218（4）, b = 9.551（3）, c = 15.877（4） A^°, β = 129.697（15）°, V = 1308.9（7） A^°^3, Z = 4, Mr = 550.79, Dc = 2.795 g/cm^3, F（000） = 995, μ（MoKa） = 14.415 mm^-1, 2（MoKa） = 0.71073 A^°, T= 293（2） K, 2θmax = 54.9°, GOOF= 1.053, the final R = 0.0310 and wR = 0.0742 for 2547 observed reflections with I 〉 2σ（I） （refinement on F^2）. Complex 1 is connected through hydrogen bonds to give a one-dimensional supramolecular chain structure. Furthermore, π-π interactions are also found between the pyrimidine rings with the center-to-center distances of 3.439（4） and 3.603（4） A^°, so complex 1 expands the chains into a two-dimensional network.     

Crystal Structure and Spectroscopic and Coordination Properties of Bis（4-fluorobenzohydroxamato）dimethyltin（Ⅳ）

An organotin（Ⅳ） complex [（CH3）2Sn（4-FC6H4CONHO）2] has been synthesized and characterized by elemental analysis, IR, ^1H NMR and X-ray single-crystal diffraction techni- ques. The crystal belongs to the orthorhombic system, space group Pbca with a = 9.7565（13）, b = 17.664（2）, c = 20.784（3）A, Z = 8, V = 3581.9（8）A^3 Dc = 1.695 g/cm^3,μ（MoKa） = 1.469 mm^-1, F（000） = 1808, R = 0.0321 and wR = 0.0838. In the molecular structure of the title complex, the tin atoms are five-coordinated in a trigonal bipyramidal geometry, and the special coordination properties of dimethyltin（Ⅳ） with hydroxamate-type ligands are also discussed.     

Synthesis and Crystal Structure of a Novel Binuclear Copper（Ⅱ） Complex, [Cu（paba）Cl]

A novel binuclear Cu（Ⅱ） complex [Cu（paba）Cl] （pabaH = 2-（2-pyridylmethylimine）benzenesulfonic acid） has been synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction. The crystal of the title complex crystallizes in a monoclinic system, space group P21/n, with a = 6.8165（7）, b = 15.3073（16）, c = 12.3795（13） A^°, β= 95.0160（10）°, V= 1286.8（2） A^°^3, Mr = 360.26, Dc= 1.860 g/cm^3,μ = 2.074 mm^-1, F（000） = 724, Z = 4, the final R = 0.0252 and wR = 0.0675 for 2395 observed reflections with I 〉 20（I）. The title complex is centrosymmetric and a pair of chlorides act as μ2-bridges to link two Cu（Ⅱ） ions forming a binuclear complex. Every Cu（Ⅱ） ion is five-coordinated by pyridyl N, imine N and sulfonate O atoms of the tridentate paba ligand as well as two bridging Cl^-, constructing the distorted square-pyramidal geometry. In the structure extensive hydrogen bonds and weak π-π stacking stabilize the solid structures, through which the complex builds its 3-dimensional supramolecular structure.     

Synthesis and Crystal Structure of [K（2,2,2-crypt）]2HP11

[K（2,2,2-crypt]2HP11 has been prepared from the reaction of K3P11 with the mixed ethylenediamine/2,2,2-crypt solution. The crystal structure was determined by singlecrystal X-ray diffraction. The crystal is of tdgonal system, space group P^-3c1 with a = 12.068（2）, b = 12.068（2）, c = 22.319（6）A, V = 2815.0（10）A^3, Dc = 1.384 g/cm^3, C36h73K2N4O12P11, Mr = 1172.85, F（000） = 1232,μ = 0.536 mm^-1, Z= 2, R = 0.0678 and wR = 0.2211 for 1763 observed reflections （I 〉 2σ（I））. In this compound, the P11 cluster has ideal 32-D3 symmetry, and the three-fold axis, corresponds to the crystallographic c axis. The （HP11）^2- anions are stable due to the completely sequestered alkali metal cations through only ion-ion interactions.     

Synthesis,Structure, Electrochemistry and Fluorescence Properties of a One-dimensional Coordination Polymer {[ CdLu-（4,4＇-dps） ]2（H2O）2]＇（4＇abs ）2（H2O）2

A new cadmium（N） compound, {[ CdLu-（4,4＇-dps） ]2（H2O）2]＇（4＇abs ）2（H2O）2n 1 （4,4＇-dps = 4,4＇-dipyridylsulfide, 4-abs = deprotonated 4-amino benzenesulfonic acid）, has been synthesized and structurally characterized. It belongs to the orthorhombic system, space group Pbcn with a = 19.950（3）, b = 10.6381（13）, c = 18.055（2）A, V= 3831.8（8） A3, Z = 4, C32H36CdN6010S4, Mr = 905.31, F（000） = 1848, μ= 0.850 mm^-1, Dc = 1.569 Mg/m^3, the final R = 0.0238 and wR = 0.0589 for 3080 observed reflections with I 〉 2σ（I）. Complex I is a one-dimensional linear chain coordination polymer and the repeat unit is comprised of doubly charged cadmium complex cation, uncoordinated 4-aminobenzene sulfonate anions and water molecules. The cadmium（H） ion adopts a six-coordinate distorted octahedral geometry. Complex 1 is stabilized and linked into a three-dimensional layered structure through intermolecular O-H…O and N-H…O hydrogen bonds together with electrostatic force. The cyclic voltammograms and fluorescence spectrum of 1 were also measured. It shows one irreversible redox process and emits a very strong and sharp fluorescent band at about 341 nm.     

Synthesis,Crystal Structure and Biological Activity of a Novel Complex： Co（L）2（CH3OH）2Cl2 （L = 3-（1,2,4-Triazole-yl）-6-chloro-pyridazine）

The title compound, Co（L）2（CH3OH）2Cl2 （L = 3-（1,2,4-triazole-yl）-6-chloro-pyridazine） 1, has been synthesized and its crystal structure has been determined by X-ray analysis. Complex 1 crystallizes in the triclinic system, space group P1 with a = 6.018（3）, b = 9.832（5）, c = 9.921（5）A, a = 78.270（8）, β = 74.550（8）, γ = 83.807（8）°, V = 553.1（5）A^3, Z = 1, C14H16Cl4CoN10O2, Mr = 557.10, Dc = 1.673 g/cm^3, F（000） = 281,μ（MoKα） = 1.293 mm^-1, the final R = 0.0453 and wR = 0.1181 for 1539 observed reflections with I 〉 2σ（I）. The Co（II） ion is in a distorted centrosymmetric six-coordinate octahedral environment with two Ntriazole, two Omethanol and two Cl atoms. Via hydrogen bonds the configuration of 1 has been extended into 1D chains which are developed to 2D layers via π-π sticking action, and these layers are further extended into a 3D network by hydrogen bonds. The antibacterial activity of the title compound has been detected, and the results show that the ligands and cobalt（II） complex exhibit certain fungicidal activity against several bacteria. Furthermore, the spectral properties of the title compound have been also studied and discussed.     

Catalytic Kinetic on the Thermal Decomposition of Ammonium Perchlorate with a New Energetic Complex Based on 3,5-Bis(3-pyridyl)-1H-1,2,4-triazole

A new energetic complex,[Co(3,3?-Hbpt)(Htm)]·H_2O(1,3,3?-Hbpt = 3,5-bis(3-pyridyl)-1H-1,2,4-triazole and H_3tm = trimesic acid),has been synthesized by hydrothermal reactions and characterized by single-crystal X-ray diffraction,elementary analysis,IR spectroscopy,thermogravimetric analysis and X-ray powder diffraction. Single-crystal X-ray diffraction indicates that the complex belongs to triclinic system,space group P 1 with a = 10.0911(1),b = 10.2573(1),c = 10.6393(1) ?,α = 103.793(2),β = 101.041(2),γ = 107.918(3)o,V = 974.9(2) ?~3,Z = 2,D_c = 1.732 g·cm-3,μ = 0.941 mm~(-1),M_r = 508.31,F(000) = 518,the final R = 0.0523 and wR = 0.0935 with I 2σ(I). In the title complex,Co(Ⅱ) ions are connected by Htm2-anions generating 1D ladder-like chains which are linked by 3,3?-Hbpt to form 1D cages. In addition,the thermal decomposition of ammonium perchlorate(AP) with complex 1 was explored by differential scanning calorimetry(DSC). AP is completely decomposed in a shorter time in the presence of complex 1,and the decomposition heat of the mixture is 2.531 kJ·g~(-1),significantly higher than that of pure AP. By Kissinger's method,the ratio of Ea/ln(A) is 11.05 for the mixture,which indicates that complex 1 shows good catalytic activity toward the AP decomposition.     

Quantum Chemistry Studies on the Fe-Cu Interactions and 31p NMR in Fe（CO）3（Ph2Ppy）2（CuXn） （Xn = Cl2^2-, Cl-, Br-）

In order to study the Fe-Cu interactions and their effects on 31p NMR, the structures of mononuclear complex Fe（CO）3fPhzPpy）a 1 and binuclear complexes Fe（CO）3（PhEPpy）z（CuXn） （2： Xn = Cl2^2-, 3： Xn = Cl-, 4： Xn = Br-） are calculated by density functional theory （DFT） PBE0 method. For complexes 1, 3 and 4, the 31p NMR chemical shifts calculated by PBE0-GIAO method are in good agreement with experimental results. The 31p chemical shift is 82.10 ppm in the designed complex 2. The Fe-Cu interactions （including Fe→Cu and Fe←Cu charge transfer） mainly exhibit the indirect interactions. Moreover, the Fe-Cu（I） interactions （mostly acting as σFe-p→4Scu and aFe-C→4Scu charge transfer） in complexes 3 and 4 are stronger than Fe-Cu（Ⅱ） interactions （mostly acting as σFe-p→4Scu and σFe-p←4Sc,） in complex 2. In complex 2, the stronger Fe←Cu interac- tions, acting as σFe-p←44SCu charge transfer, increase the electron density on P nucleus, which causes the upfield 31p chemical shift compared with mononuclear complex 1. For 3 and 4, although a little deshielding for P nucleus is derived from the delocalization of σFe-p→4Scu due to the Fe→Cu interactions, the stronger σFe-c→np charge-transfer finally increases the electron density on P nucleus. As a result, an upfield 31p chemical shift is observed compared with 1. The stability follows the order of 2〉3=4, indicating that Fe（CO）3（PhzPpy）2（CuCl2） is stable and could be synthesized experimentally. The N-Cu（Ⅱ） interaction plays an important role in the stability of 2. Because the delocalization of σFe-p→4SCu and σFe-c→πc-o weakens the a bonds of Fe-C and ~r bonds of CO, it is favorable for increasing the catalytic activity of binuclear complexes. Complexes 3 and 4 are expected to show higher catalytic activity compared to 2.     

Synthesis and Crystal Structure of a New Threedimensional Thiocyanate Supramolecular Compound [Cd（phen）（NCS）（SCN）]n

The compound [Cd（phen）（NCS）（SCN）]n（phen = 1,10-phenanthroline） was synthe- sized under hydrothermal conditions and characterized by IR and single-crystal X-ray diffraction. The complex is of monoclinic, space group C2/c with a = 14.607（3）, b = 10.505（2）, c = 10.631（2）A,β = 115.14（3）^o, V = 1476.8（5）A^3, C14H8CdN4S2, Mr = 408.76, Z = 4, F（000） = 800, μ = 1.757 mm^-1 and Dc = 1.839 g/cm^3. The final R = 0.0409 and wR = 0.0811 for 1367 observed reflections （I 〉 2σ（I））. In the title compound, each cadmium atom is six-coordinated and connected with two adjacent metal ions by two NCS bridges, creating a zigzag chain. The neighboring chains are linked to each other by the weak van der Waals＇ S…S interactions and π…π interactions to form a new three-dimensional supramolecular framework.     

Synthesis and Crystal Structure of a Zeolite-like Metal-organic Framework Based on the Triazole Ligand

A novel zeolite-like metal-organic framework, [Cd12（trz）12＇F10＇（SiF6）3]·（H3O）4 （Htrz = 1,2,4-triazole）, has been synthesized under solvothermal conditions using 1H-l,2,4-triazole-3- carboxylic acid and CdF2 as the starting materials. The complex has been characterized by elemental analysis, IR, SEM-EDS, gas adsorption, powder and single-crystal X-ray diffraction analyses. The title complex crystallizes in the cubic 1-43m space group, with a = 14.6436（8）, V= 3140.1（3）A3, Z = 2, Mr = 2857.96, D,.= 3.023 g/cm3 and F（000） = 2668. The final R = 0.0653 and wR = 0.1880 for 586 observed reflections with 1 〉 2σ（I）. In the title complex, three adjacent Cd（ll） centers are connected by three p3-bridging triazole ligands to form triagonal secondary building units （SBUs）, which are further interconnected to form a three-dimensional skeleton with tetrahedral cages.     

Hetero-bimetallic Complex of a 2D Coordination Network Constructed by Sodium Ion and p-Sulfonatothiacalix[4]arene

A 2D coordination polymer built by sodium ion and water-soluble p-sulfonatothiacalix[4]arene of trivalent yttrium complex [Na（H2O）2Y（H2O）6（DMF） （p-sulfonatothiaca lix[4]arene）]-9H2O is reported. The complex belongs to the monoclinic system, space group P2 1/c, with a = 16.703（3）, b = 17.819（4）, c = 17.357（4）A, β = 106.23（3）°, Z = 4, V = 4960.0（17）A^3, Mr = 1304.08, Dc = 1.746 g/cm^3,μ= 1.624 mm^-1, F（000） = 2688, the final R = 0.0398 and wR = 0.1132 for 7534 observed reflections with I 〉 2σ（I）. One yttrium（Ⅲ） ion is coordinated by the thiacalixarene ligand via the sulfonato group, and also ligated by an oxygen atom of a DMF molecule occupying the cavity of thiacalixarene and six aqua ligands.     

A Potassium Organic-inorganic Hybrid Complex with Channels Hosting Decorated Poly-anion Chains

A potassium organic-inorganic hybrid complex {H2[K（PMo12O40）（CH3CN）3]- （dpdo）2（H2O）}n 1 （dpdo = 4,4＇-bipyridine-N,N＇-dioxide） with special channels for the chain-like assembly of decorated Keggin-type anions was synthesized and structurally characterized. The crystal structure was determined by single-crystal X-ray diffraction. The crystal is of orthorhombic, space group Cmcm with a = 20.5328（17）, b = 16.8877（14）, c = 16,1454（14） A, V = 5598.4（8） A^3, Z = 4, C26H29N7O45KMo12P, Mr= 2380.91, Dc = 2.825 g/cm^3,μ = 2.813 mm^-1, F（000） = 4528, the final R = 0.0324 and wR = 0.0880 for 2577 observed reflections with I 〉 2σ（I）. Compound 1 exhibits a 3D network structure with large channels hosting decorated poly-anion chains as guests.     

1-D Open-channeled 3-D Supramolecular Frameworks Built with 2,3-Dihydroxybutanedioic Acid （H4dhbd） and 2,2＇：6＇,2＇＇-Terpyridine （tpy）

The complex [Cu2（H2dhbd）2（tpy）2]·CH3OH·4H2O 1 （H4dhbd =2,3-dihydroxybutanedioic acid, tpy = 2,2＇：6＇,2＇＇-terpyridine） has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis. The crystal is of triclinic, space groups Pi with a= 8.6859（17）, b = 11.223（2）, c = 12.275（2）A, α = 112.454（3）, β= 98.435（3）, γ = 105.593（3）°, V= 1022.5（3） A^3, Z = 1, C38H42Cu2N6O18, Mr = 997.86, Dc = 1.621 g/cm^3, μ= 1.127 mm^-1, F（000） = 514, T = 293（2） K, the final R = 0.0539 and wR = 0.1394 for 3550 observed reflections with I 〉 2σ（I）. In the dinuclear unit, two Cun atoms are bridged by two H2dhbd chelate anions, forming a 14-membered ring, in which the distance of Cu…Cu atoms is 7.0526（12）A. Adjacent dinuclear units are constituted through π-π interactions and C-H…O hydrogen-bonding interactions, fashioning the final 3-D supramolecular framework with 1-D open channels. Variable-temperature magnetic susceptibility measurement indicates the presence of weak antiferromagnetic exchange interactions between Cu^II ions.