The first molecular superconductor based on BEDT-TTF radical cation salt with the paramagnetic tris(oxalato)ruthenate anion, β′′-(BEDT-TTF)₄K_x(H₃O)_1−x[Ru^III(ox)₃]C₆H₅Br (x ∼ 0.8), is synthesized and its crystal and electronic structure as well as transport and magnetotransport properties are studied. The single crystals have monoclinic C2/c symmetry and β′′-packing of the conducting BEDT-TTF layer. The samples were found to be superconductors with T_c = 2.8–6.3 K (depending on the sample). Well pronounced Shubnikov–de Haas oscillations are observed in the field range 7–17 T. The Fourier spectrum of the oscillations mainly consists of two frequencies, which correspond to the Fermi surface cross sections 6.3% and 0.85% of the Brillouin zone. The first one with good accuracy corresponds to the calculated cross section 7.5%, the origin of the second one is discussed. Semiconducting orthorhombic phase ‘pseudo-κ’-(BEDT-TTF)₄K_x(H₃O)_1−x[Ru^III(ox)₃]C₆H₅CN is also synthesized and studied.

A modified procedure for the electrocrystallization of organic conductors with paramagnetic anions of the (BEDT-TTF)₄A^I[M^III(C₂O₄)₃]·G family has been proposed. It is found that single crystals of different phases of the family can be prepared if the electrocrystallization medium is represented by the mixture of 1,2,4-trichlorobenzene (or 1,3-dibromobenzene), 96% ethanol and different solvents (G), only the latter being included into the composition of the resulting salts as neutral guest molecules (G = benzonitrile, fluorobenzene, chlorobenzene, 1,2-dichlorobenzene, bromobenzene, nitrobenzene). Using this approach, a number of known and new BEDT-TTF salts with the tris(oxalato)ferrate anion have been synthesized. Among them, there are superconducting crystals of monoclinic β′′-series with different guest solvents (G) and their mixtures. For the first time, crystals of a triclinic phase (G = 1,2-dibromobenzene), with alternating α- and ‘pseudo-κ’ BEDT-TTF layers and metallic behaviour down to 1.5 K, were obtained. Additionally, monoclinic crystals having another stoichiometry and α-type donor packing were prepared.

New crystals (1–4) of organic conductors based on the radical cation salts of the bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with paramagnetic and diamagnetic tris(oxalato)metallate anions {A⁺[M³⁺(ox)₃]³⁻G}²⁻, where M is Cr, Ga; G is 2-chloropyridine, 2-bromopyridine; and A⁺ is [K_0.8(H₃O)_0.2]⁺ have been prepared and their crystal structure and transport properties were studied. All crystals belong to the monoclinic group of the (BEDT-TTF)₄A⁺[M³⁺(ox)₃]G family with β″-packing type of conducting BEDT-TTF layers. In contrast to the known superconducting crystals with M³⁺ = Fe³⁺ and G = 2-chloro- or 2-bromopyridine (T_c = 4.0–4.3 K), crystals with Cr³⁺ and Ga³⁺ ions exhibit metallic properties down to 0.5 K without superconducting transition. Upon cooling these crystals, the incommensurate superstructure appears, which has never been observed before in the numerous β″-salts of the family. In addition, orthorhombic (sp. group Pbca) semiconducting crystals α″-(BEDT-TTF)₅[Ga(ox)₃]·3.4·H₂O·0.6 EtOH (5) were obtained. It is a new compound in the family of BEDT-TTF crystals with tris(oxalato)metallate anions.

The first mononuclear anionic erbium complex [Er(hfac)₄]⁻ (hfac = hexafluoroacetylacetone) with an organic ammonium cation [(CH₃)₄N⁺] as the counterion was synthesized and structurally and magnetically characterized. The coordination geometries around the Er ions are square antiprisms with pseudo-D_4d symmetry. The complex shows distinct field-induced slow magnetization relaxation, which is described by a combination of Orbach (U_eff/k_B~28.54(8) K.) and direct mechanisms. Quantum chemical calculations were performed to analyze the magnetic properties of the complex under consideration.