László Kótai

Hungarian Academy of Sciences | HAS · Institute of Materials and Environmental Chemistry

A temperature controlled carbonization process (5-800 °C for 1-4 h) of metal forms of various types of partially or completely saturated sulphonated styrene-divinylbenzene copolymer based ion-exchangers loaded with various valence state metal ions has been evaluated. The effect of temperature, nature and valence of metal ions, cross-linking and oth...

A review. Potassium permanganate is one of the most widely used chems. in chem. and chem. industry, however, the available information about the chem. of other permanganate compds. has not been reviewed. In this paper synthetic methods and reactivity of simple and complex permanganates other than the potassium salt are critically reviewed. Generali...

Biobutanol proved to be a superior fuel substitute and blending component in gasolines or diesel fuels. It can be used as raw material in the preparation of so-called butyl-diesel (longchain fatty acid butyl esters), in the butoxylation of unsaturated fatty acid esters and in the preparation of dibutoxy-acetals. Butanol can easily be transformed vi...

The cobalt manganese oxides, especially the spinels and related (multiphase) materials described with the formula CoxMn3–xO4 (0 < x < 3), are widely used catalysts in a range of processes in significant industrial and environmental areas. The great diver-sity in the phase relations, composition, and metal ion valences, together with ion and va-canc...

The increase in the risks of mosquito-transmitted serious diseases or viral infections generates strong motivations to find new and efficient solutions for controlling blood-sucking mosquitoes. There are selective protein toxins such as BTI (Bacillus thüringiensis israelensis) used to kill mosquito larvae, which require carrier materials that keep...

Mössbauer spectra of Fe III complex salts with urea-related ligands show a broadened line due to magnetic relaxation. The origin of the relaxation is not known, mostly spin–spin type is considered. A study of a large number of compounds can be helpful to show differences in the Mössbauer parameters and to see the infuence of the chemical environmen...

An environmentally benign and expeditious protocol was developed for the one‐pot multicomponent synthesis of 4‐aryl‐3‐methylisoxazol‐5(4H)‐ones by the condensation of aldehyde, hydroxyl amine hydrochloride, and ethyl acetoacetate in 50% aq. ethanol at 50 °C. The reaction was catalyzed by magnetically separable carbon microspheres co‐decorated with...

A unique compound (compound 1) with structural features including an unprecedented tridentate-bridging coordination mode of permanganate ions and an eight-coordinated (rhombohedral) κ1-chlorido and tridentate permanganato ligand in a potassium complex containing coordination polymer (CoIII(NH3)6]n[(K(κ1-Cl)2(μ2,2′,2″-(κ3-O,O′,O″-MnO4)2)n∞) with iso...

We have developed a convenient route to transform biomass power plant ashes (BPPA) into porous sponge-like fertilizer composites. The absence of water prevents the chemical reaction and carbon dioxide formation when concentrated sulfuric acid is mixed with BPPA and CaCO3. Adding water, however, initiates the protonation reaction of carbonate ion co...

Complexes of transition and non-transition metals with a wide variety of N-donor ligands (like ammonia, amines, urea derivatives, Schiff bases, or N-heterocycles) comprise a highly important class of compounds in chemistry, biochemistry, material science, and the chemical industry [...]

Carbonatotetraamminecobalt(III)] permanganate monohydrate was synthesized first in the metathesis reaction of [Co(NH3)4CO3]NO3 and NaMnO4 in aqueous solution. Its thermal dehydration at 100 °C resulted in phase-pure [Co(NH3)4CO3]MnO4 (compound 1). Compounds 1 and 2 (i.e., the hydrated form) were studied with IR, far-IR, and low-temperature Raman sp...

Due to their Fe- and N-containing reactive urea ligand content, the hexakis(urea-O)iron(II) and hexakis(urea-O)iron(III) complexes were found to be versatile materials in various application fields of industry and environmental protection. In our present work, we have comprehensively reviewed the synthesis, structural and spectroscopic details, and...

We have described a new route for the preparation of partially methylated polygalacturonic acid containing hydrolyzed (acidic) and unhydrolyzed (methyl esterified) carboxylate groups in a ratio of 1:1 (PGA, compound 1), and one of its basic FeIII—salts (compound 2) with a ~1:2 FeIII:GA stoichiometry (GA means galacturonic acid and methylated galact...

Thermal processing of Zr-loaded ion-exchangers is a facile route to synthetize (ZrO2, ZrC)@C composites. In the present paper, furnace and RF-thermal plasma processing of ZrOCl2 loaded thiourea-functionalized styrene-divinylbenzene copolymer was investigated and led to composites containing ZrO2 and ZrC. Different ZrO2@C composites were formed betw...

Raman studies on carbon-containing phases in nanosized-ZrO2/C and nanosized-(ZrC,ZrO2)/C composites. / A. Martiz, A. Farkas, Z. Karoly, F. P. Franguelli, S. K. Samaniego, A. Menyhard, L. Kotai. / Nano Studies. – 2021–2022. – # 21/22. – pp. 177-186. – eng. Raman spectroscopic studies were performed to identify the nature of the carbon-containing pha...

Thermal processing of Zr-loaded ion-exchangers is a facile route to synthetize (ZrO2, ZrC)@C composites. The chemical character of the functional groups in the cation exchanger is an essential factor in the composition and properties of the (ZrO2, ZrC)@C composites. In the present paper furnace and RF-thermal plasma processing of ZrOCl2 loaded thio...

Citation: Béres, K.A.; Homonnay, Z.; Bereczki, L.; Dürvanger, Z.; Petruševski, V.M.; Farkas, A.; Kótai, L. Crystal Nanoarchitectonics and Characterization of the Octahedral Iron(III)-Nitrate Complexes with Isomer Dimethylurea Ligands. Abstract: Three octahedral iron(III) nitrate complexes with dimethylated urea ligand isomers, [hex-akis(N,N'-dimeth...

Three ammonium-iron-sulfites (AIS) from a burning coal dump in an abandoned open coal pit at Pécs-Vasas (Mecsek Mountains, South Hungary) were identified: (NH4)9Fe³⁺(SO3)6 (AIS-1), (NH4)2Fe²⁺(SO3)2 (AIS-2), and (NH4)2Fe³⁺(OH)(SO3)2·H2O (AIS-3). They were formed by the interaction of decomposing iron sulfides and ammonia released from organic matter...

[�2-O,O0-Carbonatotetraamminecobalt(III)] iodide, or [Co(NH3)4CO3]I, named in this paper as compound 1, was prepared and characterized comprehensively with spectroscopic (IR, Raman and UV) and single-crystal X-ray diffraction methods. Compound 1 was orthorhombic, and isomorphous with the analogous bromide. The four ammonia ligands and the carbonate...

Copper manganese oxide spinels and related (multiphase) materials with the formula Cu x Mn 3−x O 4 are the active catalysts in a wide variety of industrially important processes due to their great diversity in their phase relations, metal ion valence/site distribution, and chemical properties. In this review, we summarize the preparation methods an...

Structural and spectroscopic characterization (SXRD, IR, liq. N2 temperature Raman, UV) of hexaamminecobalt(III) dibromide permanganate, [Co(NH3)6]Br2(MnO4) (compound 1), are described. There is a 3D hydrogen bond network including N?H???O?Mn and N?H???Br interactions, which could serve as potential reaction centres for solid-phase redox reactions...

Structural and spectroscopic characterization (SXRD, IR, liq. N 2 temperature Raman, UV) of hexaamminecobalt(III) dibromide permanganate, [Co(NH 3) 6 ]Br 2 (MnO 4) (compound 1), are described. There is a 3D hydrogen bond network including N-H···O-Mn and N-H···Br interactions, which could serve as potential reaction centres for solid-phase redox rea...

Amorphous calcium carbonate (ACC) is a precursor material that plays a key role in polymorph selection and crystallization of carbonates. It is involved in the formation of the cryogenic carbonate ikaite (CaCO 3 ·6H 2 O), but the role of ACC during the transformation of this room-temperature-metastable material is poorly understood. We report the o...

We synthesized and characterized (IR, Raman, UV, SXRD) hexaamminecobalt(III) dichloride permanganate, [Co(NH3)6]Cl2(MnO4) (compound 1) as the precursor of Co–Mn–spinel composites with atomic ratios of Co:Mn = 1:1 and 1:3. The 3D−hydrogen bond network includes N–HO–Mn and N–HCl interactions responsible for solid-phase redox reactions between the per...

Anhydrous hexakis(urea-O)iron(III)]peroxydisulfate ([Fe(urea-O)6]2(S2O8)3 (compound 1), and its deuterated form were prepared and characterized with single-crystal X-ray diffraction and spectroscopic (IR, Raman, UV, and Mössbauer) methods. Six crystallographically different urea ligands coordinate via their oxygen in a propeller-like arrangement to...

Anhydrous hexakis(urea-O)iron(III)]peroxydisulfate ([Fe(ureaO)6]2(S2O8)3 (compound 1), and its deuterated form were prepared and characterized with single-crystal X-ray diffraction and spectroscopic (IR, Raman, UV, and Mössbauer) methods. Six crystallographically different urea ligands coordinate via their oxygen in a propeller-like arrangement to...

Research on new reaction routes and precursors to prepare catalysts for CO2 hydrogenation has enormous importance. Here, we report on the preparation of the permanganate salt of the urea-coordinated iron(III), [hexakis(urea-O)iron(III)]permanganate ([Fe(urea-O)6](MnO4)3) via an affordable synthesis route and preliminarily demonstrate the catalytic...

A hemipyridine solvate of bis(pyridine)silver(I) perchlorate, [Agpy2ClO4]·0.5py (compound 1) was prepared and characterized by single crystal X-ray analysis and vibrational spectroscopy (R and low-temperature Raman). Compound 1 was prepared via the trituration of [Agpy2ClO4] and 4[Agpy2ClO4]·[Agpy4]ClO4 (as the source of the solvate pyridine) in a...

Tetrapyridinesilver(I) perrhenate [Agpy4]ReO4 was synthesized, and its crystal structure and Ra-man spectra were elucidated at low temperatures. The crystal lattice is constructed from isolated tetrahe-dral cations and anions having no argentophilic interactions. Weak hydrogen bonds are formed between the oxygens of the disordered perrhenate anions...

We have developed an easy route to prepare (nano-ZrO2,nano-ZrCx)@C composites with varying ZrO2/ZrCx content. The process consists of preparing a zirconium-loaded, iminodiacetate-functionalized styrene-divinylbenzene (STY-DVB) copolymer, and its subsequent carbonization in a tube furnace and/or a thermal plasma reactor. Depending on the zirconium s...

We have developed a simple method to prepare nano-(ZrC 0.93 , ZrO 2- polymorphs)@carbon composites with graphite/amorphous carbon content and adjustable Zr/C ratio based on using a multistep tube furnace and plasma-assisted heat treatment of zirconium-loaded sulfonated styrene–divinylbenzene (STY-DVB) copolymers. Pre-pyrolysis of zirconium-loaded s...

We synthesized and structurally characterized the previously unknown [Co(NH3)5Cl](MnO4)2 complex as the precursor of CoMn2O4. The complex was also deuterated, and its FT-IR, far-IR, low-temperature Raman and UV-VIS spectra were measured as well. The structure of the complex was solved by single-crystal X-ray diffraction and the 3D-hydrogen bonds we...

We reviewed the synthesis, structure, and properties of pyridine complexes of AgXO4 (X = Cl, Mn, and Re) compounds with various compositions ([AgPy2] XO4, [AgPy2XO4]·0.5Py, [AgPy4] XO4, and 4 [AgPy2XO4] [AgPy4] XO4). We also clarified the controversial information about the existence and composition of pyridine complexes of silver permanganate, use...

Nickel nanoparticles are gaining increasing attention in catalysis due to their versatile catalytic action. A novel, low-cost and facile method was developed in this work to synthesize carbon microsphere-supported metallic nickel nanoparticles (Ni-NP/C) for heterogeneous catalysis. The synthesis was based on carbonizing a polystyrene-based cation e...

We prepared and characterized a high-t tetragonal polymorph of diamminesilver(I) sulfate (a = 8.6004(4) Å, c = 6.2123(6) Å) (compound 1-HT). The phase transformation of the low-temperature polymorph of diamminesilver(I) sulfate (compound 1-LT) into the high-temperature polymorph (compound 1-HT) partly coincides with the initial stage of the thermal...

Oxidation of thioglycolic, thiolactic and thiomalic acids by pyridinium dichromate (PDC) in dimethylsulphoxide (DMSO) leads to the formation of disulphide dimmers. The reaction is first order in PDC. Michaelis-Menten type of kinetics is observed with respect to the thioacids. Reaction is failed to induce the polymerisation of acrylonitrile. The rea...

A rapid and efficient one-pot three-component synthesis of 2-amino-3-cyano-4-aryl-7-methyl-5-oxo-4,5-dihydro-pyrano-[3,2-c]pyran and 2-amino-3-cyano-4-aryl-6-methyl5,6-dihydro-5-oxo-4H-pyrano-[3,2-c]quinoline derivatives catalyzed by copper nanoparticles grafted on carbon microspheres is developed. The use of heterogeneous catalyst, mild reaction c...

An aerial humidity-inducedsolid-phase hydrolytic transformation of the [Zn(NH3)4]MoO4@2H2O (compound 1@2H2O) with the formation of [(NH4)xH(1􀀀x)Zn(OH)(MoO4)]n (x = 0.92–0.94) coordination polymer (formally NH4Zn(OH)MoO4, compound 2) is described. Based on the isostructural relationship, the powder XRD indicates that the crystal lattice of compound...

Coronavirus disease 2019 (Covid-19) is caused by the Severe Acute Respiratory Syndrome-Corona Virus-2 (SARS-CoV-2) was firstly identified in the city of Wuhan of China in December 2019, which was spread and become a global issue due to its high transmission rate. To date, the outbreak of COVID-19 has resulted in infection to 150,356,672 people and...

The reaction of ammoniacal AgNO3 solution (or aq. solution of [Ag(NH3)2]NO3) with aq. NaClO4 resulted in [Ag(NH3)2]ClO4 (compound 1). Detailed spectroscopic (correlation analysis, IR, Raman, and UV) analyses were performed on [Ag(NH3)2]ClO4. The temperature and enthalpy of phase change for compound 1 were determined to be 225.7 K and 103.04 kJ/mol,...

The 1:1 type double salt of AgNO 3 and NH 4 NO 3 (NH 4 NO 3 ·AgNO 3 , compound 1 ) was prepared and its Raman spectrum was evaluated. IR and far‐IR spectra of compound 1 and its deuterated analog (ND 4 NO 3 ·AgNO 3 , compound 1‐D ) were also studied. We identified two types of nitrate ions, one had a relatively strong, whereas the other is only wea...

The cover picture shows the arrangement of polyoxotungstate cages in the lattice of decakis(dimethylammonium)[dihydrogendodecatungstate] polymorphs, strong multifurcated bounds of cations and some water molecules via hydrogen bonds (represents by chains), which hinder free proton‐deuterium isotope exchange. Inside the unit cells, there are water cl...

Two monoclinic polymorphs of [Ag(NH3)2]MnO4 containing a unique coordination mode of permanganate ions were prepared, and the high-temperature polymorph was used as a precursor to synthesize pure AgMnO2. The hydrogen bonds between the permanganate ions and the hydrogen atoms of ammonia were detected by IR spectroscopy and single-crystal X-ray diffr...

Two monoclinic polymorphs of [Ag(NH3)2]MnO4 containing a unique coordination mode of permanganate ions were prepared, and the high-temperature polymorph was used as a precursor to synthesize pure AgMnO2. The hydrogen bonds between the permanganate ions and the hydrogen atoms of ammonia were detected by IR spectroscopy and single-crystal X-ray diffr...

This study aims to describe the thermal decomposition of two solvatomorphs of decakis(dimethylammonium) dihydrogendodecatungstate ((Me 2 NH 2 ) 10 H 2 W 12 O 42 ·10H 2 O and 11 H 2 O) under inert and oxidizing atmospheres. Thermal studies have been done by TG-MS, TG-DSC-MS, XRD and IR methods in both synthetic air and helium atmospheres. The genera...

Two polymorphs and a solvatomorph of a new dimethylammonium polytungstate-decakis(dimethylammonium) dihydrogendodecatungstate, (Me2NH2)10(W12O42)xnH2O (n = 10 or 11)-have been synthesized. Their structures were characterized by single-crystal X-ray diffraction and solid-phase NMR methods. The shape of the dodecatungstate anions is essentially the s...

Copper manganese oxides (CMO) with CuMn2O4 composition are well-known catalysts, which are widely used for the oxidative removal of dangerous chemicals, e.g., enhancing the CO to CO2 conversion. Their catalytic activity is the highest, close to those of the pre-crystalline and amorphous states. Here we show an easy way to prepare a stable CMO mater...

Molecular iodine contributes significantly to organic transformations in synthetic organic chemistry. It works effectively due to its mild Lewis acidic character, ability as an oxidizing agent, good moisture stability, and easy availability.

Infrared and Raman spectra of two solvatomorphs of a new dimethylammonium polytungstate decakis(dimethylammonium) dihydrogendodecatungstate, (Me2NH2)(H2W12O42)·nH2O (n = 10 or 11), were evaluated and discussed. The assignment of bands corresponding to the cationic and anionic components as well as the water of crystallization is presented. Deuterat...

Detailed vibrational (IR, Raman, far-IR) and thermal (TGA, TG–MS, DSC) analysis has been performed on di[κ1O,κ2O-carbonatotetraamminecobalt(III)] sulfate trihydrate, ([Co(NH3)4CO3]2SO4·3H2O (1). Its isothermic heating at 100 °C leads to formation of [Co(NH3)4CO3]2SO4 (compound 2). UV and IR studies showed that the distorted octahedral arrangement a...

There is broad consensus that many bones of extinct vertebrates contain Rare Earth Elements (REE) and other trace minerals that have been incorporated and enriched into the fossil during diagenesis. During fossilization, apatite minerals in vertebrate bones recrystallize from metastable biogenic forms to thermodynamically more stable inorganic apat...

The novel corona virus-2 (n-CoV-2) identified in the December 2019 which then spread worldwide has become pandemic in the form of Corona virus disease 2019 (COVID-19) and affected the health, economy and the medical system to a significant extent. As on date, around 8.20 million confirmed cases including death of around 443,815 have been reported....

Amorphous calcium carbonate (ACC) is a precursor of crystalline calcium carbonates that plays a key role in biomineralization and polymorph evolution. Here, we show that several bacterial strains isolated from a Hungarian cave produce ACC and their extracellular polymeric substance (EPS) shields ACC from crystallization. The findings demonstrate th...