This article presents a simple method for synthesizing 2-arylquinoxalines by the condensation of substituted phenacyl bromides with o-phenylenediamines, catalyzed by carbon microspheres decorated with copper nanoparticles as a reusable heterogeneous catalyst. This approach is advantageous due to its environmentally friendly nature, high yield, reduced reaction time, low cost, mild reaction conditions, use of a recyclable heterogeneous catalyst, and simple workup procedure. The catalyst can be easily recovered from the reaction mixture by simple filtration and can be reused up to five catalytic cycles without a significant decrease in catalytic performance, which makes the developed protocol efficient and economical.

$${^{99\text {m}}}$$Technetium Pyrophosphate ($${^{99\text {m}}}$$Tc-PYP(Sn)) is a commonly used radioactive tracer, with a long history of use in diagnosing bone-related diseases and a newfound purpose in differentiating ATTR and AL amyloidoses. Despite its ubiquity, basic aspects like its composition and structure are as of yet undetermined, and its method of binding to ATTR amyloid fibrils is likewise hitherto unknown. This complicates the diagnostic process, as it introduces inexplicable losses of sensitivity in some ATTR and AL variants. In this paper we report the results of our comprehensive investigation into the physiologically active structure of Tc-PYP and its closely related, but experimentally more approachable counterpart, Re-PYP, built on a robust theoretical basis and backed up by multiple spectroscopic methods (focusing on the rhenium analogue). We conclude that the Re/Tc-PYP tracers possess a flexible geometry, but ultimately appear as octahedral Re(IV)/Tc(IV) diaqua dipyrophosphate complexes under physiological conditions, and predict that this structure is the reason for the high affinity of $$\phantom{0}^{99m}$$Tc-PYP for certain amyloids.

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 diversity in the phase relations, composition, and metal ion valences, together with ion and vacancy site distribution variations, results in great variety and activity as catalysts in various industrially important redox processes such as the removal of CO or volatile organic substances (VOCs) from the air and oxidative destruction of pollutants such as dyes and pharmaceuticals from wastewater using peroxides. These mixed oxides can gain application in the selective oxidation of organic molecules like 5-hydroxyfurfural or aromatic alcohols such as vanillyl alcohol or in the production of fuels and other valuable chemicals (alcohols, esters) with the Fischer–Tropsch method. In this review, we summarize these redox-based reactions in light of the chemical and phase composition of the catalysts with the formula CoxMn3−xO4 with 0 < x < 3.

Energy-saving and cost-efficient reaction routes to prepare highly active catalysts for CO2 hydrogenation or solid oxide fuel cells (SOFCs) are enormously important. In this paper, we report a detailed study of a dichromate salt of [Fe(urea)6]3+, a member of the [M(urea)6]3+ complex family (M = Fe, Al, Mn, Cr, V, or Ti) with oxidizing anions, which is a promising precursor of a Cr-rich mixed chromium iron oxide catalyst prepared at a low temperature in the solid phase. The single-crystal X-ray structure, various (infrared, ultraviolet-visible, and Raman) spectroscopic studies, and thermal analysis (differential scanning calorimetry and thermogravimetric analysis/mass spectrometry) of [hexakis(urea-O)iron(III)] dichromate {[Fe(urea-O)6]2(Cr2O7)3} and its decomposition products confirmed the presence of a quasi-intramolecular redox reaction between the urea ligands and dichromate anions. The redox reactions result in various mixed Cr-Fe oxides with amorphous structure, whereas above 550 degrees C, the crystal structure and composition of the final products depend on the atmosphere during the thermal decomposition. The iron-chromium mixed oxides are potential catalysts in CO2 hydrogenation that afford CO, CH4, C2H6, and C3H8. Furthermore, our Mossbauer spectroscopy studies show a possible electron hopping between the FeII and FeIII ions at the tetrahedral sites of the spinel structure, which suggests that the formed chromite is also a potential SOFC material. Our study also demonstrates that hexaureairon(III) dichromate is a selective oxidation agent of sulfur-containing organic compounds.

A wide variety of complexes containing N-donor ligands from ammonia, amines, Schiff bases or N-heterocycles have been prepared since the first complex compound of the family, which was an ammonia cobalt complex, was discovered [...]

The structure of hexakis(urea-O)iron(III) nitrate is found to be incommensurately modulated. It is described in (3 + 1)-dimensional superspace adopting the superspace group C2/c(sigma 10 sigma 3)00 with the modulation wavevector q = -0.7394(7)a & lowast; +0.9390(8)c & lowast; . Up to the third-order satellite reflections are observed in the diffraction data collected at 100 K. Consequently, there is an anharmonic displacive modulation present in the hexacoordinated iron(III) complex. Nitrate ions are found in two symmetrically independent sites in the unit cell and form two disordered ensembles with three disordered components and two disordered components, respectively. The latter site is located near a 2-fold axis, resulting in a total of four disorder components for this molecular site. Along with the displacive modulation for the nitrate ions, there is also a complex occupational modulation present. Possible origins of the modulation are discussed.

Calcium carbonate (CaCO3) is a dominant component of sedimentary rocks and biogenic structures, and is one of the most frequently studied inorganic compounds. It also plays a key role in preparing modern engineered materials. CaCO3 has three well-known polymorphs, calcite, aragonite, and vaterite, and four solvatomorphs with diverse crystallographic arrangements, hydration states, reactivity, and stability. Its solvatomorphs include the variable water-containing amorphous calcium carbonate (ACC—CaCO3·xH2O) and the crystalline monohydrocalcite (MHC—CaCO3·H2O), calcium carbonate hexahydrate (ikaite—CaCO3·6H2O), and the recently reported hemihydrate (CCHH—CaCO3·0.5H2O). Here, we review the preparation, crystal structure, and properties of these solvatomorphs and discuss their mutual transformations.

[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 spectroscopies, and their vibrational modes were assigned. The lattice parameters were determined by powder X-ray diffraction (PXRD) and single crystal X-ray diffraction (SXRD) methods for the triclinic and orthorhombic compounds 1 and 2, respectively. The detailed structure of compound 2 was determined, and the role of hydrogen bonds in the structural motifs was clarified. UV studies on compounds 1 and 2 showed the distortion of the octahedral geometry of the complex cation during dehydration because of the partial loss of the hydrogen bonds between the crystal water and the ligands of the complex cation. The thermal decomposition consists of a solid phase quasi-intramolecular redox reaction between the ammonia ligands and permanganate anions with the formation of ammonia oxidation products (H2O, NO, N2O, and CO2). The solid phase reaction product is amorphous cobalt manganese oxide containing ammonium, carbonate (and nitrate) anions. The temperature-controlled thermal decomposition of compound 2 in toluene at 110 °C showed that one of the decomposition intermediates is ammonium nitrate. The decomposition intermediates are transformed into Co1.5Mn1.5O4 spinel with MnCo2O4 structure upon further heating. Solid compound 2 gave the spinel at 500 °C both in an inert and air atmosphere, whereas the sample pre-treated in toluene at 110 °C without and with the removal of ammonium nitrate by aqueous washing, gave the spinel already at 300 and 400 °C, respectively. The molten NH4NO3 is a medium to start spinel crystallization, but its decomposition stops further crystal growth of the spinel phase. By this procedure, the particle size of the spinel product as low as ~4.0 nm could be achieved for the treatments at 300 and 400 °C, and it increased only to 5.7 nm at 500 °C. The nano-sized mixed cobalt manganese oxides are potential candidates as Fischer-Tropsch catalysts.

Mössbauer spectra of FeIII 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 environment on the relaxation. We have evaluated the Mössbauer spectra of 13 compounds recorded at various temperatures with the Blume–Tjon two-state relaxation model and with the (unrestricted) Afanasev–Gorobchenko model. The latter showed significant differences between some salts, and proved the presence of spin–lattice relaxation.

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 content and starts CO2 evolution. The key element of the method was that the BPPA and, optionally, CaCO3 and/or CaSO4·0.5H2O were mixed with concentrated sulfuric acid to make a paste-like consistency. No gas evolution occurred at this stage; however, with the subsequent and controlled addition of water, CO2 gas evolved and was released through the channels developed in the pastry-like material due to the internal gas pressure, but without foaming. Using a screw-containing tube reactor, the water can be introduced under pressure. Due to the pressure, the pores in the pastry-like material became smaller, and consequently, the mechanical strength of the granulated and solidified mixture became higher than that of the reaction products prepared under atmospheric pressure. The main reaction products were syngenite (K2Ca(SO4)2·H2O) and polyhalite (K2Ca2Mg(SO4)4·2H2O). These compounds are valuable fertilizer components in themselves, but the material’s porous nature helps absorb solutions of microelement fertilizers. Surprisingly, concentrated ammonium nitrate solutions transform the syngenite content of the porous fertilizer into ammonium calcium sulfate ((NH4)2Ca(SO4)2·2H2O, koktaite). Koktaite is slightly soluble in water, thus the amount of ammonium ion released on the dissolution of koktaite depends on the amount of available water. Accordingly, ammonium ion release for plants can be increased with rain or irrigation, and koktaite is undissolved and does not decompose in drought situations. The pores (holes) of this sponge-like fertilizer product can be filled with different solutions containing other fertilizer components (phosphates, zinc, etc.) to adjust the composition of the requested fertilizer compositions for particular soils and plant production. The method allows the preparation of ammonium nitrate composite fertilizers containing metallic microelements, and various solid sponge-like composite materials with adjusted amounts of slowly releasing fertilizer components like syngenite and koktaite.

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 isolated regular octahedral hexamminecobalt(III) cation was synthesized with a yield of >90%. The structure was found to be stabilized by mono and bifurcated N-H∙∙∙Cl and N-H∙∙∙O (bridging and non-bridging) hydrogen bonds. Detailed spectroscopic (IR, far-IR, and Raman) studies and correlation analysis were performed to assign all vibrational modes. The existence of a resonance Raman effect of compound 1 was also observed. The thermal decomposition products at 500 °C were found to be tetragonal nano-CoMn2O4 spinel with 19–25 nm crystallite size and KCl. The decomposition intermediates formed in toluene at 110 °C showed the presence of a potassium- and chloride-containing intermediates combined into KCl during aqueous leaching, together with the formation of cobalt(II) nitrate hexahydrate. This means that the CoIII–CoII redox reaction and the complete decomposition of the permanganate ions occurred in the first decomposition step, with a partial oxidation of ammonia into nitrate ions.

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 degrees C. The reaction was catalyzed by magnetically separable carbon microspheres co-decorated with nanosized iron sulfide and magnetite nanoparticles in 10 wt% amount. The FeS1-x-Fe3O4/C nanocatalyst was prepared from iron(III) sulfate loaded iminodiacetate group functionalized styrene-divinylbenzene based ion exchanger by pyrolysis reaction performed at 600 degrees C for 4 h. The use of magnetically separable heterogeneous catalyst, aqueous ethanol, short reaction time (30 min), and nonchromatographic purification methods are the striking features of the developed protocol. The isolated yield of the condensation products varied between 81% and 96%. Furthermore, the protocol exhibits high functional group tolerance and includes the use of noncorrosive, nonhazardous reaction conditions affording the product in excellent yields and short reaction time. A green protocol has been developed for the synthesis of 4-aryl-3-methylisoxazol-5(4H)-ones from aldehyde, hydroxyl amine hydrochloride, and ethyl acetoacetate catalyzed by magnetically separable iron-based heterogeneous catalyst. It includes noncorrosive, nonhazardous conditions affording the products in excellent yields and short reaction time. image

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 thermal properties of hexakis(urea-O)iron(II) and hexakis(urea-O)iron(III) salts with different anions (NO3-, Cl-, Br- I-, I-3(-)-, ClO4-, MnO4-, SO42-, Cr2O72-, and S2O82-). We compared and evaluated the structural, spectroscopic (IR, Raman, UV-vis, Mo''ssbauer, EPR, and X-ray), and thermogravimetric data. Based on the thermal behavior of these complexes, we evaluated the solid-phase quasi-intramolecular redox reactions of anions and urea ligands in these complexes and summarized the available information on the properties of the resulting simple and mixed iron-containing oxides. Furthermore, we give a complete overview of the application of these complexes as catalysts, reagents, absorbers, or agricultural raw materials.

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 the active ingredient on the surface of the water where the mosquito larvae feed. Environmentally friendly and effective composite carrier materials consisting of gypsum and perlite with controlled floating and sinking times were developed. The partial closing of open pores with modified cellulose derivatives as carboxymethyl cellulose (CMC) or cricket made from corn starch and hot water were used to ensure the slow dissolution of “CMC corks” in the pores, which can control the floating and sinking properties as well. The carrier composites were combined with BTI toxins such as 4% Vectobac WP (5000 ITU (international toxic unit)) toxin, resulting in a 90–100% killing rate against different tests (Culex pipiens) and various naturally abundant mosquito larva species. The stability test of the BTI-containing new carrier materials shows good applicability at flooded/dried/re-flooded areas where the flooding is temporary thus the composites can be applied as preventive treatment as well.

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 [...]

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 galacturonic acid units). The partially hydrolyzed pectin was transformed into compound 1 with the use of double ion exchange with a strongly acidic macroreticular sulfonated styrene–divinylbenzene copolymer as a hydrogen ion source. The reaction of compound 1 with FeCl3 resulted in compound 2. Compound 2 has a polymeric nature and contains binuclear FeIII(µ-O)(µ-OH)FeIII core units with two kinds of distorted octahedral iron geometries. The salt-forming acidic and methylated GA units of compound 1 are coordinated to FeIII centers in asymmetric bidentate-chelating and -bridging (via C=O group and glycosidic oxygen) modes, respectively. Two kinds of outer-sphere chloride anions were also detected by XPS in various chemical environments fixed by different sets of hydrogen bonds. We also observed a partial reduction of FeIII into FeII due to the ring-opening of the chain-end GA units of compound 1. This reaction provides a new route to determine the number of chain-ends in compound 2, and with the use of the number of GA units calculated from charge neutrality, the average length of these chains and the average molecular weight were also determined. The average molecular weight of the partially methylated polygalacturonic acid used in the industrial-scale production of commercial anti-anemic iron–polygalacturonate agents was ~50,000 g/mol. Compound 2 was also characterized by IR, Mössbauer, and X-ray photoelectron spectroscopy, and magnetic susceptibility measurements. These results on the structure and average molecular weight of basic iron(III) polygalacturonate provide a tool to design Fe-PGA complexes with tuned iron-releasing properties.

Ikaite formation and its transformation to calcite occurs via distinct amorphous calcium carbonates (referred to as I and II) that differ in their morphology, particle size, water content and stability.