Czech Academy of Sciences, Institute of Inorganic Chemistry

The promising drug candidate indazolium trans-[tetrachlorobis(1H-indazole)ruthenate(III)] (KP1019) is the second Ru-based anticancer agent to enter clinical trials. In this review, which is an update of a paper from 2006 (Hartinger et al., J. Inorg. Biochem. 2006, 100, 891-904), the experimental evidence for the proposed mode of action of this coordination compound is discussed, including transport into the cell via the transferrin cycle and activation by reduction. The results of the early clinical development of KP1019 are summarized in which five out of six evaluated patients experienced disease stabilization with no severe side effects.

Catalytic hydrogenation and dehydrogenation reactions form the core of the modern chemical industry. This vast class of reactions is found in any part of chemical synthesis starting from the milligram-scale exploratory organic chemistry to the multi-ton base chemicals production. Noble metal catalysis has long been the key driving force in enabling these transformations with carbonyl substrates and their nitrogen-containing counterparts. This review is aimed at introducing the reader to the remarkable progress made in the last three years in the development of base metal catalysts for hydrogenations and dehydrogenative transformations.

We have investigated the interaction of oligonucleotides and their alkylating derivatives with mammalian cells. In experiments with L929 mouse fibroblast and Krebs 2 ascites carcinoma cells, it was found that cellular uptake of oligodeoxynucleotide derivatives is achieved by an endocytosis mechanism. Uptake is considerably more efficient at low oligomer concentration (less than 1 microM), because at this concentration a significant percentage of the total oligomer pool is absorbed on the cell surface and internalized by a more efficient absorptive endocytosis process. Two modified proteins were detected in mouse fibroblasts that were treated with the alkylating oligonucleotide derivatives. The binding of the oligomers to the proteins is inhibited by other oligodeoxynucleotides, single- and double-stranded DNA, and RNA. The polyanions heparin and chondroitin sulfates A and B do not inhibit binding. These observations suggest the involvement of specific receptor proteins in binding of oligomers to mammalian cells.

MnOx/C and Me-MnOx/C (Me = Ni, Mg) electrocatalysts prepared by chemical deposition of manganese oxide nanoparticles on carbon have been characterized by Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), and chemical analysis. Their Oxygen Reduction Reaction (ORR) kinetics and mechanism have been investigated in alkaline KOH solutions by using the Rotating Disk Electrode (RDE) and the Rotating Ring-Disk Electrode (RRDE) setups. Doping the MnOx/C nanoparticles with nickel or magnesium divalent cations can considerably improve their oxygen reduction activity. As a result, the Me-MnOx/C electrocatalysts exhibit ORR specific or mass activities close to the benchmark 10 wt % Pt/C from E-TEK. At low ORR current densities, the undoped MnOx/C electrocatalyst displays a reaction order with respect to PO2 and OH- of 1 and −0.5, respectively, while ∂E/∂log i is ca. −59 mV dec-1. The ORR reaction order toward OH- is unchanged with the magnesium doping, while it becomes −2 with the nickel doping. RRDE data show that doping the MnOx/C electrocatalysts directs the ORR toward the four-electron pathway. The first electrochemical step of the 4-electron ORR mechanism is probably the quasiequilibrium proton insertion process into MnO2 leading to MnOOH, while the second electron transfer, consisting of the O2,ads species electrosplitting, yielding Oads and hydroxide anion, is rate determining. The presence of the doping metal cations may stabilize the intermediate MnIII/MnIV species, which assist this second charge transfer to oxygen adatoms. As a result, the ORR rate is enhanced for the Me-MnOx/C electrocatalysts: they exhibit remarkable ORR catalytic activity and yield quantitative formation of OH- (selectivity toward the 4-electron pathway).

Graphene quantum dots is a class of graphene nanomaterials with exceptional luminescence properties. Precise dimension control of graphene quantum dots produced by chemical synthesis methods is currently difficult to achieve and usually provides a range of sizes from 3 to 25 nm. In this work, fullerene C60 is used as starting material, due to its well-defined dimension, to produce very small graphene quantum dots (∼2-3 nm). Treatment of fullerene C60 with a mixture of strong acid and chemical oxidant induced the oxidation, cage-opening, and fragmentation processes of fullerene C60. The synthesized quantum dots were characterized and supported by LDI-TOF MS, TEM, XRD, XPS, AFM, STM, FTIR, DLS, Raman spectroscopy, and luminescence analyses. The quantum dots remained fully dispersed in aqueous suspension and exhibited strong luminescence properties, with the highest intensity at 460 nm under a 340 nm excitation wavelength. Further chemical treatments with hydrazine hydrate and hydroxylamine resulted in red- and blue-shift of the luminescence, respectively.

BACKGROUND: Graphene oxide composites with photocatalysts may exhibit better properties than pure photocatalysts via improvement of their textural and electronic properties. RESULTS: TiO2-Graphene Oxide (TiO2 - GO) nanocomposite was prepared by thermal hydrolysis of suspension with graphene oxide (GO) nanosheets and titania peroxo-complex. The characterization of graphene oxide nanosheets was provided by using an atomic force microscope and Raman spectroscopy. The prepared nanocomposites samples were characterized by Brunauer-Emmett-Teller surface area and Barrett-Joiner-Halenda porosity, X-ray Diffraction, Infrared Spectroscopy, Raman Spectroscopy and Transmission Electron Microscopy. UV/VIS diffuse reflectance spectroscopy was employed to estimate band-gap energies. From the TiO2 - GO samples, a 300 μm thin layer on a piece of glass 10×15 cm was created. The photocatalytic activity of the prepared layers was assessed from the kinetics of the photocatalytic degradation of butane in the gas phase. CONCLUSIONS: The best photocatalytic activity under UV was observed for sample denoted TiGO_100 (k = 0.03012 h-1), while sample labeled TiGO_075 (k = 0.00774 h-1) demonstrated the best activity under visible light.

Intense ultrasound in a pressurized batch reactor was used for preparation of monolayered MoS2 nanosheets from natural mineral molybdenite. Exfoliation of bulk MoS2 using ultrasound is an attractive route to large-scale preparation of monolayered crystals. To evaluate the quality of delamination, methods like X-ray diffraction, Raman spectroscopy and microscopic techniques (TEM and AFM) were employed. From single- or few-layered products obtained from intense sonication, MoS2 quantum dots (MoSQDs) were prepared by a one-pot reaction by refluxing exfoliated nanosheets of MoS2 in ethylene glycol under atmospheric pressure. The synthesised MoSQDs were characterised by photoluminescence spectroscopy and laser-scattering particle size analysis. Our easy preparation leads to very strongly green luminescing quantum dots.

Recently observed rapid climate changes have focused the attention of researchers and river managers on the possible effects of increased flooding frequency on the mobilization and redistribution of historical pollutants within some river systems. This text summarizes regularities in the flood-related transport, channel-to-floodplain transfer, and storage and remobilization of heavy metals, which are the most persistent environmental pollutants in river systems. Metal-dispersal processes are essentially much more variable in alluvia than in soils of non-inundated areas due to the effects of flood-sediment sorting and the mixing of pollutants with grains of different origins in a catchment, resulting in changes of one to two orders of magnitude in metal content over distances of centimetres. Furthermore, metal remobilization can be more intensive in alluvia than in soils as a result of bank erosion, prolonged floodplain inundation associated with reducing conditions alternating with oxygen-driven processes of dry periods and frequent water-table fluctuations, which affect the distribution of metals at low-lying strata. Moreover, metal storage and remobilization are controlled by river channelization, but their influence depends on the period and extent of the engineering works. Generally, artificial structures such as groynes, dams or cut-off channels performed before pollution periods favour the entrapment of polluted sediments, whereas the floodplains of lined river channels that adjust to new, post-channelization hydraulic conditions become a permanent sink for fine polluted sediments, which accumulate solely during overbank flows. Metal mobilization in such floodplains takes place only by slow leaching, and their sediments, which accrete at a moderate rate, are the best archives of the catchment pollution with heavy metals.

Nonstoichiometric TiO2–graphene nanocomposite was prepared by thermal hydrolysis of suspension with graphene nanosheets and titania–peroxo complex. The characterization of graphene nanosheets was provided by using an atomic force microscope (AFM). The prepared samples were characterized by Brunauer–Emmett–Teller (BET) surface area and Barrett–Joiner–Halenda porosity (BJH), X-ray diffraction (XRD), infrared spectroscopy (IR), Raman spectroscopy (RS), and transmission electron microscopy (TEM). UV/vis diffuse reflectance spectroscopy was employed to estimate band gap energies. From the titania/graphene samples, a 300 μm thin layer on a piece of glass 10 × 15 cm was created. The photocatalytic activity of the prepared layers was assessed from the kinetics of the photocatalytic degradation of butane in the gas phase. With regard to the degree of mineralization of butane, the sample labeled TiPC0100 and containing 0.1 g of graphene nanosheets then can be considered as the most active sample.

Electrical double layer defines the reaction environment by influencing transport of CO ₂ , local pH, electrical field strength and solvent polarization.

Abstract The photophysical and electron transfer properties of the lowest excited state of nine ruthenium (polypyridine) complexes have been characterized. The complexes studied are Ru (bpy) 3‐n (LL) 2+ n , where n varies from 0 to 3, and LL is 4, 4′‐di‐ t ‐butyl‐2,2′‐bipyridine (DTB‐bpy), 3, 3′‐dimethyl‐2, 2′‐bipyridine (DM‐bpy), or a 2, 2′‐diquinolyl derivative (DMCH). The results obtained show that the Ru (bpy) 2 (DMCH) 2+ complex is expected to be a more efficient mediator than Ru (bpy) 2+ 3 in the water‐splitting reaction by solar energy.

The topic of the review is the electrochemical analysis of solids aimed to identify or determine their phase or elemental composition, analyse the composition of solid mixtures, characterise their electrochemistry-related properties and analyse the redox state of the constituent elements. The ways of the electrode preparation are discussed with a special attention paid to compact and composite electrodes including carbon-paste electrodes, and direct immobilisation of powders on a working electrode. Examples are given of simultaneous electrochemical measurements combined with X-ray diffraction, optical or atomic force microscopy, and mass measurement by quartz microbalance. The state-of-art of voltammetric analysis of inorganic and organic solids achieved in the last two decades is systematically reviewed with the aim to find cases, when electrochemistry can compete successfully with other analytical techniques as for sensitivity, specificity, and sample consumption. Electrochemical methods are shown to be a perspective tool for redox analysis of catalysts, combined elemental and phase analysis of inorganic pigments and minerals, characterisation of solid solutions, metalloorganic and organic solids. A review with 196 references.

Nanometric particles of pure brookite TiO2 were synthesized by modified thermolysis of reactant solutions containing titania powder, HCl, urea and PEG 10000. Unique flower-like brookite agglomerates with an average diameter of ∼400–450 nm composed of single brookite nanocrystals of ∼4–5 nm were obtained at 105 °C. The brookite → rutile transformation has been studied and TiO2 mixtures with variable amount of anatase, brookite and rutile polymorphs at different temperatures (from 200 to 800 °C) were obtained. High resolution transmission electron microscopy (HRTEM), electron diffraction pattern and BET/BJH analyses were used to characterize the phase assemblages, crystallite size and pore volume of the pure-phase brookite and TiO2 mixtures. In order to understand the metastable–stable TiO2 phase transformation X-ray powder diffraction (XRD) was performed. The photoactivity of pure brookite and TiO2 powders with different compositions of the brookite–anatase–rutile and anatase–rutile polymorphs obtained during the transitions was examined by photocatalyzed degradation of 4-chlorophenols in aqueous solution. The titania sample having the highest catalytic activity was obtained at 500 °C, contained 3.2% brookite, 42.9% anatase and 53.9% rutile and is referred to as TiO[B])/500 .

Zirconium-based metal-organic frameworks were recently investigated as catalysts for degradation of organophosphate toxic compounds, such as pesticides or chemical warfare agents. The most utilized UiO-66 is considered as a stable material for these applications in an aqueous environment. However, the presented results indicate that the properties of UiO-66 are changing considerably in aqueous media under common conditions used for organophosphate degradations, and therefore its catalytic activity is not related to the number of structural defects created during the material synthesis. We delineate the stability of UiO-66 in water of various pHs, the in situ formation of new catalytic sites, and the correlation of these two parameters with the degradation rate of a model organophosphate pollutant, dimethyl-4-nitrophenyl phosphate (methyl-paraoxon). The stability was quantified using high-performance liquid chromatography (HPLC) by measuring the amounts of leached terephthalic acid, the linker of UiO-66, and monocarboxylic acids, the modulators bound at UiO-66 defects. We demonstrate that the HPLC analysis is a more suitable method for metal-organic frameworks stability assessment than commonly used methods, e.g., powder X-ray diffraction, adsorption isotherms, or electron microscopy.

The combination of zirconium-based MOF UiO-66 with buffered environment leads to UiO-66 decomposition.

Silicon nanocrystals are an extensively studied light-emitting material due to their inherent biocompatibility and compatibility with silicon-based technology. Although they might seem to fall behind their rival, namely, direct band gap based semiconductor nanocrystals, when it comes to the emission of light, room for improvement still lies in the exploitation of various surface passivations. In this paper, we report on an original way, taking place at room temperature and ambient pressure, to replace the silicon oxide shell of luminescent Si nanocrystals with capping involving organic residues. The modification of surface passivation is evidenced by both Fourier transform infrared spectroscopy and nuclear magnetic resonance measurements. In addition, single-nanocrystal spectroscopy reveals the occurrence of a systematic fine structure in the emission single spectra, which is connected with an intrinsic property of small nanocrystals since a very similar structure has recently been observed in specially passivated semiconductor CdZnSe nanoparticles. The organic capping also dramatically changes optical properties of Si nanocrystals (resulting ensemble photoluminescence quantum efficiency 20%, does not deteriorate, radiative lifetime 10 ns at 550 nm at room temperature). Optically clear colloidal dispersion of these nanocrystals thus exhibits properties fully comparable with direct band gap semiconductor nanoparticles.

Molybdenum-doped anatase was prepared by thermal hydrolysis of peroxotitanium complex aqueous solutions containing a molybdenum peroxo-complex. The synthesized samples were characterized by X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction, and surface area (BET) and porosity (BJH) determination. Molybdenum doping caused the increase of unit cell constants of anatase and changes in the morphology of particles from spindle-like shapes to the shapes with rectangular or square cross sections. The presence of Mo5+/Mo6+ ion doping in the TiO2 nanostructure has no significant effect on the transformation of anatase to rutile. In the visible region, the photocatalytic activity is substantially enhanced in the molybdenum concentration of about 1.38%. The photocatalytic activity of doped titania samples was determined by the decomposition of Orange II dye during irradiation at 365 and 400 nm. The titania sample with 1.38% Mo has the highest catalytic activity during the photocatalyzed degradation of Orange II dye in an aqueous suspension in the UV and visible regions.

A multi-parametric assessment of the impact of storage time/conditions and capping agent charge on the stability and toxicity of AgNPs showed agglomeration, dissolution, oxidation, capping agent degradation and attachment of Ag⁺ions all play a role.

HIV protease (HIV PR) is a primary target for anti-HIV drug design. We have previously identified and characterized substituted metallacarboranes as a new class of HIV protease inhibitors. In a structure-guided drug design effort, we connected the two cobalt bis(dicarbollide) clusters with a linker to substituted ammonium group and obtained a set of compounds based on a lead formula [H(2)N-(8-(C(2)H(4)O)(2)-1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))-3,3'-Co)(2)]Na. We explored inhibition properties of these compounds with various substitutions, determined the HIV PR:inhibitor crystal structure, and computationally explored the conformational space of the linker. Our results prove the capacity of linker-substituted dual-cage cobalt bis(dicarbollides) as lead compounds for design of more potent inhibitors of HIV PR.

5'-[32P]-labelled alkylating decathymidylate [4-(N-2-chloroethyl)N-methylaminobenzyl]-5'-phosphamide derivatives containing cholesterol or phenazinium residues at their 3'-termini were synthesized and used for alkylation of DNA within mammalian cells. The uptake of the cholesterol derivative by the cells and the extent of DNA alkylation are about two orders of magnitude higher than those of a similar alkylating derivative lacking the groups at the 3'-termini. The presence of the phenazinium residue at the 3'-terminus of the oligonucleotide reagent does not improve the reagent uptake by the cells but drastically increases the DNA modification efficiency.