Dinuclear and layered copper 2-pyridylphosphonates with weak ferromagnetism observed in layer compound Cu(C5H4NPO3)

Two new canted antiferromagnetic systems: magnetic, theoretical, and crystallographic studies on trans-bis(2-iodopyridine)dihalocopper(ii)

The two complexes Cu(2ip)X₂ were prepared (where 2ip = 2-iodopyridine and X = Cl or Br), and their crystal structures were determined. The two complexes are isomorphous and form a magnetic chain based on the two-halide exchange pathway. The powder and single crystal magnetic susceptibility data were measured down to 1.8 K. The exchange is antiferromagnetic along the chain; the exchange is stronger in the bromide complex than in the corresponding chloride complex. In the ordered state, weak moments appear along some of the axes, indicative of spin-canting. The calculated spin densities and the mapped surface of spin density on total electron density were used to rationalize qualitatively the observed magnetic behavior. Low temperature structures are compared with the room temperature data; the C-IX-Cu and Cu-XX-Cu distances are shorter at low temperatures; in contrast, the covalent bonds of the organic ligand (2-iodopyridine) are longer (negative thermal expansion of the covalent bonds). The anomalous behavior is rationalized using charge transfer from Cu-X group to the anti-bonding orbital of the organic ligand. Quantum theory of atoms in molecules was used to analyze C-IX halogen bonding interactions.

Cobalt and copper pyridylmethylphosphonates with two- and three-dimensional structures and field-induced magnetic transitions

Two novel metal pyridylmethylphosphonates, namely, [Co(4-pmp)] (1) and [Cu(4-pmp)(H2O)] (2), (4-pmpH2 = 4-pyridylmethylphosphonic acid), have been hydrothermally synthesized and characterized by X-ray diffraction, infrared spectroscopy, elemental analysis, and thermogravimetric analysis. In compound 1, each {PO3C} tetrahedron is corner-shared with three {CoNO3} tetrahedra and vice versa, thus forming a one-dimensional (1-D) inorganic chain along the a axis containing 8-membered rings of [(Co-O-P-O)2]. The inorganic chains are further connected by a 4-pmp(2-) ligand, generating a 2-D layered structure. Compound 2 displays a three-dimensional (3-D) framework structure, in which the inorganic layers are pillared by the pyridyl groups of the ligand, generating a 3-D pillared-layered structure. The magnetic properties of 1 and 2 have been studied. Compounds 1 and 2 behave as metamagnets at low temperature. The critical fields are about 70 kOe for 1 and 47 kOe for 2 at 1.8 K.

Explorations of new phases in the Ga(III)/In(III)-Cu(II)-Se(IV)-O system

Four new gallium(III)/indium(III), copper(II), selenium(IV) oxides, namely, Ga(2)Cu(SeO(3))(4) (1), Ga(2)CuO(SeO(3))(3) (2), and M(2)Cu(3)(SeO(3))(6) (M = Ga 3, In 4), have been synthesized by hydrothermal or high-temperature solid-state reactions. The structure of Ga(2)Cu(SeO(3))(4) (1) features a 2D layer of corner-sharing GaO(6) and CuO(6) octahedra with the SeO(3) groups hanging on both sides of the 2D layer. Ga(2)CuO(SeO(3))(3) (2) features a pillared layered structure in which the 1D Cu(SeO(3))(3)(4-) chains act as the pillars between 2D layers formed by corner- and edge-sharing GaO(n) (n = 4, 5) polyhedra. Although the chemical compositions of M(2)Cu(3)(SeO(3))(6) (M = Ga 3, In 4) are comparable, they belong to two different structural types. Ga(2)Cu(3)(SeO(3))(6) (3) exhibits a pillared layered structure built by [Ga(2)Cu(3)(SeO(3))(4)](4+) thick layers with Se(3)O(3)(2-) groups as pillars. The structure of In(2)Cu(3)(SeO(3))(6) (4) features a 3D network composed of [In(2)(SeO(3))(2)](2+) layers and [Cu(3)(SeO(3))(4)](2-) layers interconnected through Se-O-Cu and In-O-Cu bridges, exhibiting 8-MR helical tunnels along the a-axis. Results of magnetic property measurements indicate that there are considerable antiferromagnetic interactions between copper(II) centers in Ga(2)CuO(SeO(3))(3) (2) and M(2)Cu(3)(SeO(3))(6) (M = Ga 3, In 4). Interestingly, Ga(2)Cu(3)(SeO(3))(6) (3) behaves as a weak ferromagnet below the critical temperature of T(c) = 15 K. Further magnetic studies indicate that the compound is a canted antiferromagnet with a large canting angle of about 7.1 degrees.

Diaqua-bis(2-pyridylphospho-nato N-oxide-κO,O)cobalt(II)

In the title complex, [Co(C₅H₅NO₄P)₂(H₂O)₂], the Co^II ion, which lies on a crystallographic inversion center, is coordin­ated by four O atoms from two bidentate 2-phospho­nato­pyridine N-oxide ligands and two O atoms from two water ligands in a slightly distorted octa­hedral environment. Mol­ecules are inter­linked by three O—H⋯O hydrogen bonds and one weak C—H⋯O inter­action, forming a three-dimensional supra­molecular structure.

Three-Dimensional Lanthanide(III)–Copper(II) Compounds Based on an Unsymmetrical 2-Pyridylphosphonate Ligand: An Experimental and Theoretical Study

Based on an unsymmetrical 2-pyridylphosphonate ligand, two types of Ln(III)-Cu(II) compounds with three-dimensional structures were obtained under hydrothermal conditions, namely, Ln(2)Cu(3)(C(5)H(4)NPO(3))(6).4H(2)O (1.Ln; Ln=La, Ce, Pr, Nd) and Ln(2)Cu(3)(C(5)H(4)NPO(3))(6) (2.Ln; Ln=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho). Compounds 1.Ln are isostructural and crystallize in chiral cubic space group I2(1)3. In these structures, each Ln ion is nine-coordinate and has a tricapped triprismatic geometry, while each Cu center is six-coordinate with an octahedral environment. The {LnO(9)} polyhedra and {CuN(2)O(4)} octahedra are connected by edge sharing to form an inorganic open framework structure with a 3-connected 10-gon (10,3) topology in which the Ln and Cu atoms are alternately linked by the phosphonate oxygen atoms. Compounds 2.Ln are isostructural and crystallize in trigonal space group R3. In these structures, the {LnO(6)} octahedra are triply bridged by the {CPO(3)} tetrahedra by corner sharing to form an infinite chain along the c axis. Each chain is connected to its six equivalents through corner sharing of {CPO(3)} tetrahedra and {CuN(2)O(2)} planes to form a three-dimensional framework structure in which the Ln and Cu atoms are linked purely by O-P-O units. The formation of these two types of structures is rationalized by quantum chemical calculations, which showed that both the lanthanide contraction and the electron configuration of Cu(II) play important roles. When Cu(II) was replaced by Zn(II), only the first type of compounds resulted. The magnetic properties of complexes 1.Ln and 2.Ln were investigated. The nature of Ln(III)-Cu(II) (Ln=Ce, Pr, Nd) interactions is illustrated by comparison with their Ln(III)-Zn(II) analogues.

An azido–CuII–triazolate complex with utp-type topological network, showing spin-canted antiferromagnetism

An azido-metal-1,2,4-triazolate coordination polymer, [Cu(trz)(N(3))](n) (trz = 1,2,4-triazolate) was synthesized using hydrothermal methods; the complex has a rare three-dimensional non-interpenetrated utp or (10,3)-d topological network structure and exhibits spin-canted antiferromagnetism at low temperature.