Incorporation of Pyrazine and Bipyridine Linkers with High-Spin Fe(II) and Co(II) in a Metal-Organic Framework

A series of isoreticular metal-organic frameworks (MOFs) of the formula M(BDC)(L) (M = Fe(II) or Co(II), BDC = 1,4-benzenedicarboxylate, L = pyrazine (pyz) or 4,4'-bipyridine (bipy)) has been synthesized and characterized by N₂ gas uptake measurements, single crystal and powder X-ray diffraction, magnetometry, X-ray absorption spectroscopy, and Mössbauer spectroscopy. These studies indicate the formation of a permanently porous solid with high-spin Fe(II) and Co(II) centers that are weakly coupled, consistent with first-principles density functional theory calculations. This family of materials represents unusual examples of paramagnetic metal centers coordinated by linkers capable of mediating magnetic or electronic coupling in a porous framework. While only weak interactions are observed, the rigid 3D framework of the MOF dramatically impacts the properties of these materials when compared with close structural analogues.

A new cube-based dodecanuclear cobalt(ii) cluster with azide and tetrazolate ligands exhibiting ferromagnetic ordering

A novel Co₁₂ cluster was composed of three identical Co₄ cubane units bridged by μ₆-CO₃²⁻ and tetrazolate bridges and exhibits long-range ferromagnetic ordering at about 9 K.

Poly[diaqua[μ4-4-(isonicotinamido)phthalato]nickel(II)] displaying antopology

In the title compound, [Ni(C14H8N2O5)(H2O)2]n, the NiIIcation is six-coordinate with a slightly distorted octahedral coordination geometry and the 4-(isonicotinamido)phthalate ligand links the NiIIcentres into a three-dimensional structure withsratopology. The structure is also stabilized by N—H...O hydrogen bonding between the uncoordinated amide groups of the ligand and extensive O—H...O hydrogen bonding between the two coordinated water molecules. The magnetic and thermal stability properties of the title compound are also discussed.

Double single-crystal-to-single-crystal transformation and small-molecule activation in rhodium NHC complexes

Three gases, one crystal: rhodium NHC complexes undergo back-to-back single-crystal-to-single-crystal transformations by selective nonreversible ligand exchange reactions. Slow diffusion of O(2) converts a dinitrogen complex into a dioxygen complex, and CO subsequently replaces O(2).

3D Mn(II) coordination polymer with alternating azide/azide/formate/formate bridged chains: synthesis, structure and magnetic properties

A new 3D Mn(II) coordination polymer, [Mn(2)(HCO(2))(L)(2)(N(3)) x MeOH](infinity) (1) (L = nicotinate N-oxide), was synthesized by a solvothermal reaction and characterized magnetically. Complex 1 is a typical antiferromagnet with alternating azide/azide/formate/formate bridges, exhibiting a new -J(1)J(1)J(2)J(2)- coupling sequence. This is the first complex to contain an azide, formate and another type of carboxylate ligand.