Synthesis, characterization and magnetic property of a succinate bridged 1D coordination polymer of cobalt(II) containing benzidine as end-capping ligand

Antiferromagnetic Interactions through the Thirteen Å Metal-Metal Distances in Heterometallic One-Dimensional Chains

A heterometallic and paramagnetic one-dimensional aligned chain in -Rh(+2)-Rh(+2)- Pt(+2)-Ni(+2)-Pt(+2)- with direct metal-metal bonds was obtained via HOMO-LUMO interactions at the σ* (dz2) orbital between [Rh2(O2CCH3)4] and [Pt2Ni(piam)4(NH3)4] (piam=pivalamidate). The one-dimensional chains had straight backbones attributed to face-to-face stacking of each complex, and the Ni atoms were separated by approximately 13 Å from four different metals. Each Ni atom had two unpaired electrons in the d-orbitals, which strongly exchanged with J=-37.9 cm-1 through the diamagnetic -Pt-Rh-Rh-Pt- bonds.

Dimerization of Paramagnetic Trinuclear Complexes by Coordination Geometry Changes Showing Mixed Valency and Significant Antiferromagnetic Coupling through -Pt···Pt- Bonds

Paramagnetic trinuclear complexes, trans-[Pt₂M(piam)₄(NH₃)₄](ClO₄)_x (t-M; piam = pivalamidate, M = Mn, Fe, Co, Ni, and Cu, x = 2 or 3), aligned as Pt-M-Pt were successfully synthesized and characterized. The dihedral angles between the Pt and M coordination planes in t-M are approximately parallel, showing straight metal-metal bonds with distances of approximately 2.6 Å. Except for t-Fe, the trinuclear complexes are dimerized with close contact (approximately 3.9 Å) between the end Pt atoms to form Pt-M-Pt···Pt-M-Pt alignments with high-spin M(+2) containing five (t-Mn), three (t-Co), two (t-Ni), and one (t-Cu) unpaired electrons localized on M atoms. Several physical measurements and calculations revealed that the dimerized structures were maintained in MeCN, where cyclic voltammograms for t-M exhibited two-step oxidation and reduction attributed to Pt-M(+2)-Pt···Pt-M(+2)-Pt ↔ Pt-M(+3)-Pt···Pt-M(+2)-Pt ↔ Pt-M(+3)-Pt···Pt-M(+3)-Pt via mixed-valent states. Magnetic susceptibility measurements for t-M showed antiferromagnetic interaction, t-Mn: J = -0.9 cm^-1, t-Co: J = -3.5 cm^-1, t-Ni: J = -7.3 cm^-1, and t-Cu: J = 0.0 cm^-1, between the two M centers with distances of 9.0 Å through Pt···Pt bonds.

Construction of Pyrazine-Appended 1D and 3D Cobalt(II) Succinate Coordination Polymers: Influence of Solvent on Architectures and Applications in Gas Adsorption and NAC Detection

An underexplored reaction of pyrazine (rigid and linear) and succinic acid (flexible) with Co(NO₃)₂·6H₂O afforded four new coordination polymers (CPs): [Co(H₂O)(pyz)(suc)] (1), [Co(H₂O)₂(pyz)(suc)] (2), [Co(H₂O)₄(pyz)](suc) (3) and [Co₂(H₂O)₂(pyz)(suc)₂] (4), as well as [Co(HCO₂)₂(pyz)] (5) being lately reported along with well-known 6 and 7. The CPs were obtained as stable crystalline materials and characterized by conventional solid-state techniques, including X-ray crystallography. Hydrothermally produced compounds 1 and 2 were both 3D CPs. While 3 and 4 obtained under ambient/solvothermal conditions in DMSO generated 1D and 3D structures, 5 isolated from DMF under solvothermal conditions had a 3D structure. The topologies of the coordination polymers 1-7 were described by underlying nets 3D 5-c fet, 3D 4-c cds, 1D 2-c 2C1, 3D 5-c bnn, 3D 6-c rob, 1D 2-c 2C1, and 3D 6-c pcu, respectively. The plot of χ_M ^-1 versus T was essentially linear in the entire temperature range following the Curie-Weiss law with a Curie constant (C) of 2.525 and a negative Weiss constant (ϕ) of -46.24 K, suggesting weak antiferromagnetic (AF) exchange interactions. CO₂ and N₂ adsorption studies of 1-5 featured type III isotherms. 1 was found to show remarkably higher quenching efficiencies for nitrophenols (η = 98% for o-NP) over other NACs. The Stern-Volmer plot exhibited deviation in linearity with K _sv values about 200 times greater than that for the simplest nitroaromatic compound (NB), signifying its exclusive quenching ability toward 1. The LOD for p-NP addition to 1 was found to be 0.995 ppm.

Paramagnetic One-Dimensional Chain Complex Consisting of Three Kinds of Metallic Species Showing Magnetic Interaction through Metal-Metal Bonds

A heterometallic and paramagnetic one-dimensional (1-D) chain (3) aligned as -Rh(+2)-Rh(+2)-Pt(+2)-Co(+2)-Pt(+2)- with direct metal-metal bonds was obtained by HOMO-LUMO interactions at the σ* (d_z²) orbital between two kinds of complexes. The 1-D chains in 3 have relatively straight backbones because the raw material complexes, [Rh₂(O₂CCH₃)₄] and [Pt₂Co(piam)₄(NH₃)₄], are connected and stacked in a face-to-face fashion, where Co---Co are separated by about 13.3 Å with four different metals. Physical measurements revealed that 3 has a band gap between the σ-type conduction and valence bands, where d-orbitals of the Co ion with three unpaired electrons are laid among them. The magnetic behavior of 3 was investigated and found to be consistent with a complex interaction involving both zero-field splitting and Pauli paramagnetism attributed to band formation superimposed on relatively strong exchange coupling (zJ = -22.2 cm^-1) between two high-spin Co(+2) ions separated by the diamagnetic Pt-Rh-Rh-Pt.