KTm[B4O6(OH)4] ⋅ 3H2O: A New Member of Borate Family with Mica-like Tetrahedral Layers

Crystallography Reports - Crystals of new borate KTm[B4O6(OH)4] ? 3H2O (sp. gr. Р $$\bar {3}$$ 1m, a = 4.5472(7) Å, c = 12.151(3) Å) have been obtained under hydrothermal...     

Molecular Structure and Magnetic and Optical Properties of Endometallonitridofullerene Sc3N@Ih-C80 in Neutral,Radical Anion,and Dimeric Anionic Forms

A series of compounds with Sc₃N@I_h-C₈₀ in the neutral, monomeric, and dimeric anion states have been prepared in the crystalline form and their molecular structures and optical and magnetic properties have been studied. The neutral Sc₃N@I_h-C₈₀ ⋅ 3 C₆H₄Cl₂ ( 1 ) and (Sc₃N@I_h-C₈₀)₃(TPC)₂ ⋅ 5 C₆H₄Cl₂ ( 2 , TPC=triptycene) compounds both crystallized in a high-symmetry trigonal structure. The reduction of Sc₃N@I_h-C₈₀ to the radical anion resulted in dimerization to form diamagnetic singly bonded (Sc₃N@I_h-C₈₀⁻)₂ dimers. In contrast to {[2.2.2]cryptand(Na⁺)}₂(Sc₃N@I_h-C₈₀⁻)₂ ⋅ 2.5 C₆H₄Cl₂ ( 3 ) with strongly disordered components, we synthesized new dimeric phases {[2.2.2]cryptand- (K⁺)}₂(Sc₃N@I_h-C₈₀⁻)₂ ⋅ 2 C₆H₄Cl₂ ( 4 ) and {[2.2.2]cryptand- (Cs⁺)}₂(Sc₃N@I_h-C₈₀⁻)₂ ⋅ 2 C₆H₄Cl₂ ( 5 ) in which only one major dimer orientation was found. The thermal stability of the (Sc₃N@I_h-C₈₀⁻)₂ dimers was studied by EPR analysis of 3 to show their dissociation in the 400–460 K range producing monomeric Sc₃N@I_h-C₈₀^.− radical anions. This species shows an EPR signal with a hyperfine splitting of 5.8 mT. The energy of the intercage C−C bond was estimated to be 234±7 kJ mol⁻¹, the highest value among negatively charged fullerene dimers. The EPR spectra of crystalline (Bu₃MeP⁺)₃(Sc₃N@I_h-C₈₀^.−)₃ ⋅ C₆H₄Cl₂ ( 6 ) are presented for the first time. The salt shows an asymmetric EPR signal, which could be fitted by three lines. Two lines were attributed to Sc₃N@I_h-C₈₀^.−. Hyperfine splitting is manifested above 180 K due to the hyperfine interaction of the electron spin with the three scandium atoms (a total of 22 lines with an average splitting of 5.32 mT are observed at 220 K). Furthermore, each of the 22 lines is additionally split into six lines with an average separation of 0.82 mT. The large splitting indicates intrinsic charge and spin density transfer from the fullerene cage to the Sc₃N cluster. Both the monomeric and dimeric Sc₃N@I_h-C₈₀⁻ anions show an intrinsic shift of the IR bands attributed to the Sc₃N cluster and new bands corresponding to these species appear in the NIR range of their UV/Vis/NIR spectra, which allows these anions to be distinguished from neutral species.     

Abrupt Spin-State Switching in Mn(III) Complexes with BPh4 Anion: Effect of Halide Substituents on Crystal Structure and Magnetic Properties.

Three tetraphenylborates of mononuclear Mn(III) cation complexes with hexadentate ligands, the products of the reaction between a N,N′-bis(3-aminopropyl)ethylenediamine and salicylaldehydes with the different haloid substitutions at the 5 or 3,5 positions, have been synthesized: [Mn(5-F-sal-N-1,5,8,12)]BPh₄ ( 1 ), [Mn(3,5-diCl-sal-N-1,5,8,12)]BPh₄ ( 2 ) and [Mn(3,5-Br,Cl-sal-N-1,5,8,12)]BPh₄ ( 3 ). Their crystal structure, dielectric constant (ϵ) and magnetic properties have been studied. Ligand substituents have a dramatic effect on the structure and magnetic properties of the complexes. With decreasing temperature, the complex ( 1 ) shows a gradual spin crossover from the high-spin state (HS) to the HS:LS intermediate phase, followed by an abrupt transition to the low-spin state (LS) without changing the crystal symmetry. The complexes 2 and 3 are isostructural, but have fundamentally different properties. Complex 2 demonstrates two structural phase transitions related to sharp spin crossovers from the HS to the HS:LS intermediate phase at 137 K and from the intermediate phase to the LS at 87 K, while complex 3 exhibits only one spin transition from the HS to the HS:LS intermediate phase at 83 K.     

Slow Magnetic Relaxation,Antiferromagnetic Ordering,and Metamagnetism in MnII(H2dapsc)-FeIII(CN)6 Chain Complex with Highly Anisotropic Fe-CN-Mn Spin Coupling

Reactions of [Mn(H₂dapsc)Cl₂] ⋅ H₂O (dapsc=2,6- diacetylpyridine bis(semicarbazone)) with K₃[Fe(CN)₆] and (PPh₄)₃[Fe(CN)₆] lead to the formation of the chain polymeric complex {[Mn(H₂dapsc)][Fe(CN)₆][K(H₂O)_3.5]}_n ⋅ 1.5n H₂O ( 1 ) and the discrete pentanuclear complex {[Mn(H₂dapsc)]₃[Fe(CN)₆]₂(H₂O)₂} ⋅ 4 CH₃OH ⋅ 3.4 H₂O ( 2 ), respectively. In the crystal structure of 1 the high-spin [Mn^II(H₂dapsc)]²⁺ cations and low-spin hexacyanoferrate(III) anions are assembled into alternating heterometallic cyano-bridged chains. The K⁺ ions are located between the chains and are coordinated by oxygen atoms of the H₂dapsc ligand and water molecules. The magnetic structure of 1 is built from ferrimagnetic chains, which are antiferromagnetically coupled. The complex exhibits metamagnetism and frequency-dependent ac magnetic susceptibility, indicating single-chain magnetic behavior with a Mydosh-parameter φ=0.12 and an effective energy barrier (U_eff/k_B) of 36.0 K with τ₀=2.34×10⁻¹¹ s for the spin relaxation. Detailed theoretical analysis showed highly anisotropic intra-chain spin coupling between [Fe^III(CN)₆]³⁻ and [Mn^II(H₂dapsc)]²⁺ units resulting from orbital degeneracy and unquenched orbital momentum of [Fe^III(CN)₆]³⁻ complexes. The origin of the metamagnetic transition is discussed in terms of strong magnetic anisotropy and weak AF interchain spin coupling.     

A Series of Novel Pentagonal-Bipyramidal Erbium(III) Complexes with Acyclic Chelating N3O2 Schiff-Base Ligands: Synthesis,Structure, and Magnetism

A series of six seven-coordinate pentagonal-bipyramidal (PBP) erbium complexes, with acyclic pentadentate [N₃O₂] Schiff-base ligands, 2,6-diacetylpyridine bis-(4-methoxybenzoylhydrazone) [H₂DAPMBH], or 2,6-diacethylpyridine bis(salicylhydrazone) [H₄DAPS], and various apical ligands in different charge states were synthesized: [Er(DAPMBH)(C₂H₅OH)Cl] (1); [Er(DAPMBH)(H₂O)Cl]·2C₂H₅OH (2); [Er(DAPMBH)(CH₃OH)Cl] (3); [Er(DAPMBH)(CH₃OH)(N₃)] (4); [(Et₃H)N]⁺[Er(H₂DAPS)Cl₂]⁻ (5); and [(Et₃H)N]⁺[Y₀.₉₅Er₀.₀₅(H₂DAPS)Cl₂]⁻ (6). The physicochemical properties, crystal structures, and the DC and AC magnetic properties of 1–6 were studied. The AC magnetic measurements revealed that most of Compounds 1–6 are field-induced single-molecule magnets, with estimated magnetization energy barriers, U_eff ≈ 16–28 K. The experimental study of the magnetic properties was complemented by theoretical analysis based on ab initio and crystal field calculations. An experimental and theoretical study of the magnetism of 1–6 shows the subtle impact of the type and charge state of the axial ligands on the SMM properties of these complexes.     

1,2-Dioximes in the trofimov reaction

3,3′-Dimethyl-1,1′-divinyl-2,2′-dipyrrole was obtained during the reaction of 3,4-hexanedione dioximes with acetylene under pressure in the potassium hydroxide-DMSO system. In the case of 1,2-cyclohexanedione dioxime 2,2′-dipyrrole and 2-pyridyl-and 2-acylpyrroles were isolated. α-Benzil and α-furil dioximes give 3,4-diphenyl-and 3,4-di(2-furyl)-1,2,5-oxadiazoles respectively in addition to their mono-and divinyl derivatives. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 39–46, January, 2006.     

Stereospecificity of shielding constants of carbon-13 nuclei in 13C NMR spectra of oximes of hetarenecarbaldehydes and alkyl heteryl ketones

It has been discovered that the chemical shifts of carbon atoms in ¹³C NMR spectra of oximes having pyrrolyl, furyl, benzofuryl, thienyl, and pyridyl rings as substituents are changed systematically on going from the E- to the Z-isomer. This makes it possible to use the indicated chemical shifts for establishing the configuration of oximes with heterocyclic substituents and studying the special features of their electronic structure. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1523–1531, October, 2008.     

Investigation of supersmooth optical surfaces and multilayer elements using soft X-ray radiation

The aim of this work is application of soft X-ray diffuse scattering for certification of diffractiongrade optical elements and their substrates at a working wavelength. A device is suggested that allows certification under laboratory conditions owing to a dynamic range approaching that of synchrotron radiation sources. Experimental data are compared with data of alternative methods.