Protonated paramagnetic redox forms of di-o-quinone bridged with p-phenylene-extended TTF: A EPR spectroscopy study

The chemical oxidation and reduction processes of deprotonated, direduced o-quinone-exTTF-o-quinone in protic solvents were studied by EPR spectroscopy. The formation of relatively stable paramagnetic protonated redox forms of the parent triad was very surprising. The character of spin-density distribution in the semiquinone–quinone and semiquinone–catechol redox forms indicates that the p-phenylene-extended tetrathiafulvalene connector provides a quite effective electronic communication channel between dioxolene coordination sites. It was found that the deprotonated, direduced o-quinone-exTTF-o-quinone is capable to reduction of the metal copper in solution. The radical anion species formed in this reaction exists in solution as a solvent-separated ion pair with a copper cation. A character of spin-density distribution in a radical anion species leads to the conclusion that the ligand corresponds to type III of the Robin–Day classification

Sandwich Compounds of Transition Metals with Cyclopolyenes and Isolobal Boron Analogues

A series of sandwich compounds of transition metals (M=Ni, Fe, Cr) with cyclic hydrocarbon (M(CH)n) and borane (M(BH2)n), ligands (including mixed hydrocarbon/borane sandwiches) has been studied using density functional theory (B3LYP/6‐311+G(df,p)). Multicenter bonding between the central metal atom and basal cycloborane rings provides stabilization to planar cycloborane species. Large negative NICS values allude to aromatic character in the cycloboranes similar to the analogous cyclic hydrocarbons. The ability of cycloborane sandwiches to stabilize attached carbocations, radicals and carbanions is also assessed

Recognition of S···Cl Chalcogen Bonding in Metal-Bound Alkylthiocyanates

Reaction of K₂[PtCl₄] with excess AlkSCN in water gives the alkylthiocyanate complexes <i>trans</i>-[PtCl₂­(AlkSCN)₂] (Alk = Et <b>1</b>, ^<i>n</i>Pr <b>2</b>; 80–85%). These species were studied, in particular, by X-ray crystallography. In the solid state, both <b>1</b> and <b>2</b> exhibit the previously unreported S···Cl chalcogen bonding, which consolidates the complexes into networks and leads to layered structures. Theoretical density functional theory calculations and Bader’s atoms in molecules analysis demonstrated two types of intermolecular interactions in tetramer (<b>1</b>)₄, viz. the S···Cl chalcogen and the H···Cl hydrogen bonds. Despite that each particular S···Cl or H···Cl bonding is weak with the estimated energy of 1–2 kcal/mol, altogether they play a crucial role in the stabilization of the S₂Cl₂ fragment in (<b>1</b>)₄, the basis set of superposition error corrected interaction energy being −12.8 kcal/mol per monomer complex molecule. The chalcogen bonding and the rhomboidal structure of the S₂Cl₂ fragment can be interpreted in terms of electrostatic arguments as a result of the interaction between the belt of negative electrostatic potential around the Cl atoms and the sulfur σ-holes. The natural bond orbital analysis revealed that both LP­(S) → LP*­(Pt)/​σ*­(Pt–N)/​σ*­(Pt–Cl) and LP­(Cl) → σ*­(S–C) types of hyperconjugative charge transfers are important in the chalcogen bonding

Indirect Magnetic Exchange between <i>o</i>‑Iminosemiquinonate Ligands Controlled by Apical Substituent in Pentacoordinated Gallium(III) Complexes

A number of pentacoordinated gallium complexes iSQ₂GaR (<b>1</b>–<b>7</b>) (R = Et (<b>1</b>), Me (<b>2</b>), N₃ (<b>3</b>), Cl (<b>4</b>), Br (<b>5</b>), I (<b>6</b>), NCS (<b>7</b>)) where iSQ is a radical anion of 4,6-di-<i>tert</i>-butyl-<i>N</i>-(2,6-diisopropylphenyl)-<i>o</i>-iminobenzoquinone were synthesized, and crystalline samples of <b>1</b>–<b>7</b> were characterized using magnetic susceptibility measurements. The character of magnetic exchange interaction between spins of <i>o</i>-iminosemiquinonate radicals was found to be strongly influenced by the nature of the apical substituent. The antiferromagnetic coupling is predominant when the apical position is occupied by halogens or other tested inorganic anions, and the value of exchange interaction parameter varies from −99 to −176 K for R = I and NCS, respectively. In the case of alkyl groups the ferromagnetic exchange prevails and, as the result, the triplet ground state for pentacoordianted biradical compounds was observed. Compounds <b>1</b>–<b>7</b> demonstrate a biradical X-band EPR spectrum in frozen toluene matrix. The molecular structures of <b>4</b>, <b>6</b>, and <b>7</b> have been established by single-crystal X-ray analysis. A computational DFT UB3LYP/6-31G­(d,p) study was performed on complexes <b>1–7</b> in order to understand the reason for changes in the magnetic behavior of the related diradical gallium compounds. The calculations showed that the magnetic behavior of the complexes with inorganic anions is conditioned by the presence of antiferromagnetic exchange channel formed as a consequence of overlapping between donor atomic orbitals of iminoquinone with π-orbitals of halogen atoms (<b>4</b>–<b>6</b>) or nitrogen atom (<b>3</b>, <b>7</b>)

Extremely Polysubstituted Magnetic Material Based on Magnetoplumbite with a Hexagonal Structure: Synthesis, Structure, Properties, Prospects

Crystalline high-entropy single-phase products with a magnetoplumbite structure with grains in the &#956;m range were obtained using solid-state sintering. The synthesis temperature was up to 1400 &#176;C. The morphology, chemical composition, crystal structure, magnetic, and electrodynamic properties were studied and compared with pure barium hexaferrite BaFe12O19 matrix. The polysubstituted high-entropy single-phase product contains five doping elements at a high concentration level. According to the EDX data, the new compound has a formula of Ba(Fe6Ga1.25In1.17Ti1.21Cr1.22Co1.15)O19. The calculated cell parameter values were a = 5.9253(5) &#197;, c = 23.5257(22) &#197;, and V = 715.32(9) &#197;3. The increase in the unit cell for the substituted sample was expected due to the different ionic radius of Ti/In/Ga/Cr/Co compared with Fe3+. The electrodynamic measurements were performed. The dielectric and magnetic permeabilities were stable in the frequency range from 2 to 12 GHz. In this frequency range, the dielectric and magnetic losses were &#8722;0.2/0.2. Due to these electrodynamic parameters, this material can be used in the design of microwave strip devices