Homo-valent diruthenium(II,II) carbonates Na4[Ru2(CO3)4]·10H2O: synthesis, structure, properties, and calculation

Homo-valent diruthenium(II,II) carbonates have been underexplored hitherto. This paper reports the synthesis and crystal structure of a diruthenium(II,II) compound, Na₄Ru₂(CO₃)₄·10H₂O (1). It has a two-dimensional structure in which the paddle-wheel diruthenium units of Ru₂(CO₃)₄^4- are cross-linked through the carbonate groups. The investigation of the primary magnetic properties and theoretical studies with density functional theory (DFT) reveal that weak antiferromagnetic interactions are propagated between the Ru₂ units which contain two unpaired electrons in an electron configuration σ²π⁴δ²π*²δ*² with a ground state S = 1. According to Raman spectrum measurements combined with theoretical calculations, the strong peak at 356 cm^-1 in the small-wavenumber region was assigned to the stretching of the Ru-Ru double bonds.

Electronic Structure of Ru26+ Complexes with Electron-Rich Anilinopyridinate Ligands

Diruthenium paddlewheel complexes supported by electron-rich anilinopyridinate (Xap) ligands were synthesized in the course of the first in-depth structural and spectroscopic interrogation of monocationic [Ru₂(Xap)₄Cl]⁺ species in the Ru₂⁶⁺ oxidation state. Despite paramagnetism of the compounds, ¹H NMR spectroscopy proved highly informative for determining the isomerism of the Ru₂⁵⁺ and Ru₂⁶⁺ compounds. While most compounds are found to have the polar (4,0) geometry, with all four Xap ligands in the same orientation, some synthetic procedures resulted in a mixture of (4,0) and (3,1) isomers, most notably in the case of the parent compound Ru₂(ap)₄Cl. The isomerism of this compound has been overlooked in previous reports. Electrochemical studies demonstrate that oxidation potentials can be tuned by the installation of electron donating groups to the ligands, increasing accessibility of the Ru₂⁶⁺ oxidation state. The resulting Ru₂⁶⁺ monocations were found to have the expected (π*)² ground state, and an in-depth study of the electronic transitions by Vis/NIR absorption and MCD spectroscopies with the aid of TD-DFT allowed for the assignment of the electronic spectra. The empty δ* orbital is the major acceptor orbital for the most prominent electronic transitions. Both Ru₂⁵⁺ and Ru₂⁶⁺ compounds were studied by Ru K-edge X-ray absorption spectroscopy; however, the rising edge energy is insensitive to redox changes in the compounds due to the broad line shape observed for 4d transition metal K-edges. DFT calculations indicate the presence of ligand orbitals at the frontier level, suggesting that further oxidation beyond Ru₂⁶⁺ will be ligand-centered rather than metal-centered.

Interlayer hydrogen bonding directed magnetic properties for a different number of water-intercalated structural heterometallic phosphates based on paddlewheel units Ru2(PO4)46

Layered heterometallic phosphates {Mn(H2O)4}2Mn(H2O)2Ru2(PO4)4(H2O)2 (1) with a new topology were constructed from Ru2(PO4)46- and Mn2+ in the presence of anions as assisting reactants whose alkaline strength plays a key role in directing a different number of lattice water-intercalated structures. In the presence of CO32- and SO42- as assisting reactants, the assembling reaction in the aqueous solution at room temperature results in compounds 1·10H2O and 1·4H2O, respectively. Single-crystal X-ray diffraction analysis reveals that compounds 1·10H2O and 1·4H2O crystallize in orthorhombic space group Pbca and monoclinic space group P21/c, respectively. The layered structure of 1 is constructed by alternating Ru2O10 tetragonal dipyramid and MnO6 octahedra bridged by PO4 tetrahedra. The neutral heterometallic phosphate layers of 1 are separated by a different number of interlayer lattice water molecules, and hydrogen bonds are responsible for the neutral inorganic layer connection. Magnetism measurements show that compound 1·10H2O exhibits a soft magnet behaviour ordering below 8.5 K with indirect hydrogen bonding between these ferrimagnetic layers, and a reentrant spin-glass-like transition is observed for compound 1·4H2O, exhibiting two steps transition at 8.0 and 12 K, due to a strong competition between intralayer magnetic coupling and interlayer antiferromagnetic interactions mediated through the direct hydrogen bonding.

Structural diversity and magnetic properties of six ferrocenyl monocarboxylate Mn(ii), Ni(ii) and Co(ii) complexes with 1D aqua, carboxyl or dinuclear hydroxyl bridges

Six ferrocenyl monocarboxylate Mn(ii), Ni(ii) and Co(ii) complexes with different types of magnetic coupling bridges were synthesized successfully. 1–6 display intriguing structure diversity and magnetic properties.

Metal phosphonates incorporating metalloligands: assembly, structures and properties

This feature article summarizes the current status of metal–metalloligand phosphonates including the synthetic strategies, crystal structures and properties. Future challenges in this field are discussed.

Alkali counterions tune diruthenium(iii,iii)-based ferrimagnetic chain structured antiferromagnets exhibiting step-like hysteresis loops

The synthesis of antiferromagnets (AFMs) has attracted extensive attention in the area of magnetic devices, such as spintronics and memory devices. Following our initial work on the employment of the homo-valent diruthenium(iii,iii) paddle wheel species with high spin states (S = 2) as building blocks and active components for the construction of molecule-based magnetic materials, the reaction of mixed-valent diruthenium(ii,iii) phosphates Ru₂(H₂PO₄)₂(H_1.5PO₄)₂(H₂O)₂·2H₂O (1) with H₂O₂, Cu²⁺ and ACl (A = K, Rb and Cs) in aqueous solution led to the formation of heterometallic copper diruthenium(iii,iii) phosphates A₂[Cu(H₂O)₄Ru₂(HPO₄)₂(PO₄)₂(H₂O)₂]·nH₂O [A = K (2); A = Rb and n = 2 (3); A = Cs and n = 3 (4)]. The compounds consist of chain structures in which each octahedral environment of Cu(H₂O)₄²⁺ bonds to two [Ru(HPO₄)₂(PO₄)₂]^2- units in a trans manner, forming a ferrimagnetic negative chain {Cu(H₂O)₄Ru₂(HPO₄)₂(PO₄)₂(H₂O)₂}_n^2n-, exhibiting anomalous magnetic properties. Long-range ordering temperatures, T_c, were observed around 10 K, and the control of the chain structured antiferromagnets exhibiting step-like hysteresis loops was successfully achieved through counterion tuning by replacing K with either Rb or Cs.