The reduction of the heteroleptic cobalt(III) complexes with bipyridine ligands of different structures of the model drug molecule is studied by in situ NMR spectroscopy. The nature of the ligand eliminated during reduction is shown to exert a substantial effect on the reduction rate, which indicates that an optimum amount of cobalt should be chosen for the redox-activated delivery of a certain drug.

A new redox-active cobalt(III) complex containing the 2-oxo-2Н-chromene-6,7-diolate dianion and 4,4'-dimethoxy-2,2'-bipyridine as ligands is synthesized. The reduction of the synthesized complex with ascorbic acid in an inert atmosphere is studied in situ by NMR spectroscopy. The reduction is shown to result in the release of 6,7-dihydrocycoumarin acting as a model drug. This process has the first order with respect to the initial complex.

The trinuclear cobalt(III) complex [(Bipy) 5 Co 3 (L) 2 ](Cl) 3 ( I ) is synthesized by the template reaction of 2,2'-(1 H -imidazole-4,5-diyl)bis(4-ethylphenol) (L) and bis(2,2-bipyridine)cobalt(II) dichloride in the presence of diazabicycloundecene. The complex is isolated in the individual state and characterized by elemental analysis, cyclic voltammetry, UV-VIS spectroscopy, and X-ray diffraction (XRD) (CIF file СCDC no. 2201135). According to the obtained data, the cobalt ions in trinuclear complex I have the oxidation state +3, and the complex formation occurs with the oxidation of the initial cobalt(II) ions.

A possibility of generating a high degree of spin polarization of 13 C and 15 N nuclei in the cyanide ion, which forms the coordination bond with the metal ion, using parahydrogen is demonstrated for the first time for the new iridium carbene complex as an example. The spin–spin interaction constants in the synthesized complex and the structure of the hydride intermediate are determined by an analysis of the 13 С NMR spectra detected using broadband and selective heteronuclear decoupling. The cyanide ion is shown to coordinate to the metal ion by the carbon atom in one of two equatorial positions, and two pyridine molecules are arranged in the axial and equatorial positions. The signal amplification factors for 13 С and 15 N nuclei of the cyanide anion (5665 and –49 555, respectively) are estimated by NMR spectroscopy of the polarized substrate using the SABRE method from an ultralow magnetic field of 0.5 μT. This amplification corresponds to 15.5% polarization of nitrogen nuclei achieved within several seconds at room temperature.

The Pogromnoye Deposit related to gold–sulfide-quartz formation of the veinlet-disseminated ore type was formed in the shear zone that occurs between overthrusts in the block confined to the volcanogenic–sedimentary basin along the fragment of the Mongol–Okhotsk suture. The parageneses of zonal quartz–albite–micaceous (muscovite–sericite) metasomatic formation related to the profile of moderate acid leaching are presented in ore-related metasomatites. The ore-related metasomatic replacements are interpreted to be Early Cretaceous and dated as far back as 139.5 ± 1.8 Ma. The absolute age of gold-bearing stockwork formation is associated with the termination of hydrothermal ore activity of the Amudzhikan–Sretensky Complex at 131 ± 1.2 Ma. Ore minerals are dominantly arsenopyrite, pyrite, secondary sphalerite, chalcopyrite, pyrrohotite with sulfosalts, gersdorffite, accessory molybenite and magnetite. The diffusion coefficient of As was calculated in zonal metacrystals of gold-bearing arsenopyrite and pyrite in the ores. The temperature interval of gold ore deposition during the formation of ore-bearing metasomatite equal to 350–150oC is validated by the physico-chemical data on mineral equilibria and fluid inclusions and the thermodynamic calculations performed using the SELECTOR software. Gold mineralization was generated by sulfoarsenide hydrothermal solution containing gold as thioarsenites AuAs $${\text{S}}_{2}^{0}$$ and H2AuAs $${\text{S}}_{3}^{0}$$ with hydrosulfide AuHS0, concentrations of dissolved S ≥ 0.01–0.001 m and As ≥ 0.005–0.0005 m, respectively.

The article discusses a novel methodological approach to deciphering the evolution of ore-magmatic systems (OMS), based on the study of geochemical fields associated with different stages of the evolution of the magma chamber, accompanied by ore mineralization. As the material for research, we used the results of geochemical dispersion train surveys within the Kara ore cluster (Eastern Transbaikalia). The analysis of features of the composition and sequence of identification of geochemical fields made it possible to consider in more detail the evolution of the Kara OMS. It was found that we are dealing with a highly eroded rare metal OMS created in two ore formation stages. The first ore formation stage is associated with the evolution of the upper magma chamber (apical part of the Kara–Chacha massif). The main useful component of this OMS was Mo. The second stage is associated with the evolution of the lower magma chamber. This was also rare-metal mineralization; its profiling elements were W and Mo, but the main useful component is Au. It was found that Au is mobile at two evolutionary stages of the late OMS and accumulates when one stage of mineralization overprints the other. Granitoids of the Kara–Chacha massif can be considered the source of Au. No less probable is the hypothesis of its input together with B from the lower levels of the magmatic system, or as part of transmagmatic fluids from without.

Pogromnoe deposit of gold-sulfide-quartz formation of stringer-disseminated ore type is formed into shear zone between overthrusts within the block of volcanic-sediment basin along the part of the Mongol-Okhotsk suture. Paragenesises of zonal quartz-albite-mica metasomatic formation correspond to profile of the moderate acid leaching. Near ore metasomatic replacements are dated as 139.5± 1.2 Ma. The absolute age of gold-bearing stockworks formation is 131±1.2 Ma. Ore minerals are arsenopyrite, pyrite, additional sphalerite, chalcopyrite, pyrrohotite, sulfosalts, gersdorffite, rare molybdenite and magnetite. Diffusion coefficient of As was calculated into zonal metacrystals of arsenopyrite and pyrite in ores. The established temperature interval of ore gold sedimentation is based on the physico-chemical modeling with SEJEKTOR software as equal 350–150°C. The ore gold formation was generated by sulfoarsenide hydrothermal solution containing gold as AuAsS2 and H2AuAsS3 complexes for concentration of dissolved S ≥ 0.01 ÷ 0.001 m and As ≥ 0.005 ÷ 0.0005 m respectively.

Evaluation of the chromatographic properties of covalently bonded hyperbranched stationary phase based on poly(styrene-divinylbenzene) (PS-DVB) and containing zwitterionic fragments in the structure of functional layer was conducted in suppressed ion chromatography (IC), reversed phase high performance liquid chromatography (RP HPLC), and hydrophilic interaction liquid chromatography (HILIC) modes. Besides the possibility of resolving 20 inorganic anions and organic acids using KOH eluent in suppressed IC, prepared resin provided the separation of alkylbenzenes in RP HPLC, water-soluble vitamins, amino acids, and sugars in HILIC mode. Trends in the retention of hydrophobic and polar analytes on the prepared stationary phase indicated the dominating effect of analyte nature on the retention mechanism and proved satisfactory hydrophilization of PS-DVB surface with hyperbranched functional layer for retaining polar compounds. The obtained results revealed good prospects of using hydrophobic PS-DVB substrate for preparing stationary phases for mixed-mode chromatography.

—Study of granitoids spatially and genetically associated with gold mineralization within the Kara gold ore cluster has provided a new insight into their genesis, association with ore mineralization, and the sources of their ore material. The regional granitoids associated with gold mineralization are part of two individual complexes. One of them, earlier assigned to the Amanan complex, has an isotopic age of 182.9 ± 2.6 Ma and must be related to the subduction zone that existed on the southern margin of the Siberian continent in that period. Its granitoids differ in age and composition from the granitoids of the Amanan complex and must be separated as an independent taxonomic unit after an additional geological study. The second, Amudzhikan–Sretensk, complex has an isotopic age of 151.7 ± 1.9 Ma and might be related to the collision of the Siberian and Mongol–Chinese continents after the closure of the Mongol–Okhotsk ocean. In geochemistry the granitoids of the Amanan(?) complex correspond to adakites and must be considered melting products of the basaltic layer of the oceanic lithosphere. The granitoids of the Amudzhikan-Sretensk complex are similar in geochemistry to sanukitoids, melting products of subcontinental sources contaminated with continental-crust material. The granitoids of both complexes have high contents of gold and must be considered gold-bearing. In the Amanan(?) complex, adakites are the gold-richest rocks (as estimated from the slab melt composition), which indicates the primary nature of this gold. In the Amudzhikan–Sretensk complex, the highest contents of gold are specific to primitive sanukitoids, melting products of a mantle source with gold signatures. This suggests the primary nature of gold, whose content is determined by the portion of slab melt in the source of the rock material. The presence of adakites and primitive sanukitoids in the regional granitoid complexes indicates the existence of a subcontinental mantle source with gold signatures during the magma generation. The source formed in the subduction zone that existed on the southern margin of the Siberian continent in the Early Jurassic and was remobilized under collision of the Siberian and Mongol–Chinese continents in the Late Jurassic. This source might have controlled both granitoid magmatism and ore mineralization.

Four types of high-purity quartzites from the Oka–Urik block, stock quartzites of the East Sayan Urengenur block, and granular quartz of the Patom plateau (vein 2821) are investigated. The textural and structural features and mineral and fluid inclusions (FIs) are determined for all types of raw quartz material. Schemes for producing high-purity quartz concentrates are developed for each type. Optical glass samples are produced by the vacuum-compression fusion and their spectral characteristics are measured.

Pyrite crystals and ore-bearing shales of the Degdekan deposit were studied by means of XPS, SEM–EDX, EPMA, and AAS. Five peaks of carbon organic forms were identified, conforming to polymer compounds containing either double bonds of carbon or alkyne groups and compounds containing C–OH and C=O bonds, as well as, probably, small amounts of S-containing compounds and those with functional groups of carboxylic acids. Sulfate prevails over sulfite in pyrites; among the surface sulfide forms, disulfide prevails over monosulfide; the presence of polysulfide is registered. The occurrence of various chemical forms of sulfur on the surface might provide for concentrating of microelements including the noble metals (NMs) in their surface-bound forms. The regular behavior of NMs (Au, Pt, Pd, and Ru) depending on the grain sizes (specific surfaces) of pyrite crystals along with the narrow range of the ratios of structural and surface components of the concentrations of different NMs points to NM coprecipitation with pyrite during the same productive stage. No capture of NM-containing carbonaceous phases took place, which should violate the regularity of Au distribution in pyrites of the Sukhoi Log deposit.

Spatial/genetic control by slab magma products at gold deposits is shown in this paper by the example of granitoids in the Ust'-Kara area of the Eastern Trans-Baikal Region. The investigation performed makes it possible to take a fresh look at the problem of metal sources in the East Trans-Baikal gold deposits and to relate their formation to material flow from the oceanic lithosphere in the subduction zone, material conservation within the subcontinental mantle, and possible remobilization under large tectonic reconstructions.

This study provides geochemical, mineralogical, and isotope data for rocks and ores from Lower Proterozoic black shale formations of the Kodar–Udokan structural and formational zone, which host the Khadatkanda gold—uranium deposit. The results indicate that the uranium and gold mineralizations were formed at different times in relation to different geodynamic settings. The gold mineralization is associated with the inception of the Syulban fault and has a juvenile source. The later Th–U mineralization originated during tectonic rejuvenation of the Syulban fault zone, while the sources of radioactive elements were presumably the underlying sediments of the Kodar Group, which are widespread throughout the area of the Baikal mountain region (BMR). Based on the above results, the Au–U mineralization in the study area can be recognized as unconformity-type deposits, analogous to the well-known deposits of Australia and Canada. In this connection, the Baikal mountain region has a good potential for the discovery of Au—U deposits.