A combination of organic and inorganic cations in the synthesis of transition metal nitrates: preparation and characterization of canted rectangular Ising antiferromagnet (PyH)CsCo2(NO3)6

Pyridinium cesium cobalt nitrate, (PyH)CsCo2(NO3)6, obtained from a nitric acid solution crystallizes in the orthorhombic space group Pnma with unit cell parameters a = 8.6905(14) Å, b = 11.9599(18) Å, c = 18.386(3) Å, V = 1911.0(5) Å3, and Z = 4. It consists of [Co(NO3)3]- layers, in which each Co2+ ion is connected with four monodentate bridging NO3-groups and one bidentate terminal NO3-group, forming a corrugated rectangular net. Magnetization and specific heat measurements show that (PyH)CsCo2(NO3)6 undergoes a long-range canted antiferromagnetic ordering in two steps at TC1 = 5.0 K and TC2 = 2.6 K. The temperature dependence of the magnetic susceptibility and the field dependence of the magnetization measured for (PyH)CsCo2(NO3)6 show that it is an Ising antiferromagnet. In support of these observations, our DFT + U + SOC calculations show that the Co2+ ions of (PyH)CsCo2(NO3)6 have an easy-axis magnetic anisotropy with preferred spin orientation along the b-axis. To a first approximation, the spin lattice of (PyH)CsCo2(NO3)6 is a weakly alternating Ising antiferromagnetic chain (J1/J2 ∼ 0.85), and these chains interact weakly (J3/J2 ∼ 0.07) to form a rectangular Ising antiferromagnetic lattice. In agreement with the prediction for a rectangular Ising antiferromagnet by Onsager, (PyH)CsCo2(NO3)6 undergoes a long-range antiferromagnetic ordering.

A cascade of magnetic phase transitions and a 1/3-magnetization plateau in selenite-selenate Co3(SeO3)(SeO4)(OH)2 with kagomé-like Co2+ ion layer arrangements: the importance of identifying a correct spin lattice

We prepared a new compound, Co₃(SeO₃)(SeO₄)(OH)₂, having layers in a kagomé-like arrangement of Co²⁺ (spin S = 3/2) ions. This phase crystallizes in the orthorhombic space group Pnma (62) with unit cell parameters a = 11.225(9) Å, b = 6.466(7) Å and c = 11.530(20) Å. Its layers, parallel to the ab-plane, are made up of Co1O₅ square pyramids and Co2O₆ and Co3O₆ octahedra. As the temperature is lowered, Co₃(SeO₃)(SeO₄)(OH)₂ undergoes three successive magnetic transitions at 27.5, 19.4 and 8.1 K, and the magnetization of Co₃(SeO₃)(SeO₄)(OH)₂ measured at 2.4 K exhibits a 1/3-magnetization plateau between 7.8 and 19.9 T. The H-T magnetic phase diagram constructed for Co₃(SeO₃)(SeO₄)(OH)₂ from ac and dc magnetic susceptibility, specific heat and magnetization measurements contains three magnetic phases I, II and III. Phase I is antiferromagnetic, while phases II and III are ferrimagnetic and responsible for the 1/3-magnetization plateau. To interpret these complex magnetic properties, we identified the correct spin lattice for Co₃(SeO₃)(SeO₄)(OH)₂ by evaluating its intralayer and interlayer spin exchanges based on spin-polarized DFT+U calculations.

Observation of a 1/3 magnetization plateau in Pb2Cu10O4(SeO3)4Cl7 arising from (Cu2+)7 clusters of corner-sharing (Cu2+)4 tetrahedra

A mixed-valence compound Pb₂Cu₁₀O₄(SeO₃)₄Cl₇ has a complex structure consisting of one nonmagnetic Cu⁺ (S = 0) ion and four nonequivalent magnetic Cu²⁺ (S = 1/2) ions. It exhibits antiferromagnetic ordering at T_N = 10.2 K. At a temperature below T_N, a sequence of spin-flop transition at B_spin-flop = 1.3 T and 1/3 plateau formation at B_spin-flip = 4.4 K is observed in the magnetization curve M(B). The 1/3 magnetization plateau persists at least up to 53.5 T. The spin exchanges of Pb₂Cu₁₀O₄(SeO₃)₄Cl₇ evaluated by performing energy-mapping analysis based on DFT+U calculations show that the magnetic properties of Pb₂Cu₁₀O₄(SeO₃)₄Cl₇ are described by the (Cu²⁺)₇ cluster of corner-sharing (Cu²⁺)₄ tetrahedra, and that each (Cu²⁺)₇ cluster has a S = 3/2 spin arrangement in the ground state. The 1/3 magnetization plateau observed for Pb₂Cu₁₀O₄(SeO₃)₄Cl₇ is explained by the field-induced flip of every second (Cu²⁺)₇ cluster within a unit cell.

Bis(alkyl) scandium and yttrium complexes coordinated by an amidopyridinate ligand: synthesis, characterization and catalytic performance in isoprene polymerization, hydroelementation and carbon dioxide hydrosilylation

Highly versatile and robust organolanthanides as catalysts or catalyst precursors for a variety of challenging transformations.

A new Mo(iv) complex with the pentadentate (N3O2) Schiff-base ligand: the first non-cyanide pentagonal-bipyramidal paramagnetic 4d complex

A heptacoordinate complex [Mo^IV(DAPBH)Cl₂] (H₂DAPBH is 1,1'-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene)dibenzohydrazine) has been synthesized and characterized structurally and magnetically. It exhibits a slightly distorted pentagonal bipyramidal geometry and reveals paramagnetic behaviour resulting from two unpaired electrons (S = 1) with large positive zero-field splitting (D = +50 cm^-1) and pronounced temperature-independent paramagnetism.

2-Acyl-1,1,3,3-tetracyanopropenides (ATCN): structure characterization and luminescence properties of ammonia and alkali metal ATCN salts

Herein, syntheses, crystal structures, and photoluminescence properties of 24 new ammonia and alkali metal ATCN salts characterized via single-crystal X-ray diffraction are reported. Moreover, ten structure types of these salts have been described, three of which are predominant. Some ATCNs were obtained as two crystalline polymorphs. It was estimated that most ATCN powders exhibited yellow-green fluorescence (at 450-600 nm). For samples that possess fluorescence of low intensity in the solid state, several optical centers of emission exist. It was speculated that the obtained spectral features were due to anion-anion intermolecular interactions. ATCN being a new representative of stable tetracyanoallyl salts is a promising candidate for creation of various 1D, 2D, and 3D supramolecular structures and potential functional materials.

(Et4N)[MoIII(DAPBH)Cl2], the first pentagonal-bipyramidal Mo(iii) complex with a N3O2-type Schiff-base ligand: manifestation of unquenched orbital momentum and Ising-type magnetic anisotropy

We demonstrate that a planar pentadentate organic ligand can generate sufficiently strong ligand-field to stabilize the low-spin orbitally-degenerate configuration of Mo(iii) that results in strong Ising-type magnetic anisotropy.

Invariom approach to electron density studies of open-shell compounds: the case of an organic nitroxide radical

The study reports the successful modeling of electron density with invarioms for an open-shell compound, an organic nitroxide radical.

Invariom approach as a new tool in electron density studies of ionic liquids: a model case of 1-butyl-2,3-dimethylimidazolium chloride BDMIM[Cl]

In this comparative study of an ionic liquid (IL), BDMIM[Cl], the invariom approximation emerges as a useful tool in search for ‘structure–property’ relations in ILs, as entangling complex interplay of interionic interactions that operate in them.

Tuning of the double-well potential of short strong hydrogen bonds by ionic interactions in alkali metal hydrodicarboxylates

The influence of the cation nature on the peculiarities of short strong H-bonds within hydrocarboxylate crystals is revealed.