Luísa M. D. R. S. Martins

Sulfur rich fuels produce harmful gaseous oxides on combustion leading to significant environmental and mechanical problems. Conventional desulfurization methods are often time and energy intensive, lack effective catalyst-oxidant synergy and are not readily applicable to real transportation fuels. Herein, a hausmannite manganese (Mn3O4) driven copper oxide (CuO) based C3N4 composite-sodium hypochlorite (Mn₃O₄-CuO/C₃N₄-NaClO) system was developed for the oxidative desulfurization (ODS) of naphthenic sulfur compounds in transportation fuels. The metal oxides were synthesized using a wet impregnation technique while C₃N₄ was prepared using urea as the precursor. The synthesized catalysts were characterized using various techniques which confirmed the incorporation of Mn3O4 and CuO species, and the uniform modification of the morphology and surface characteristics of pristine C₃N₄, resulting in enhanced crystallinity and surface functionalities. The Mn₃O₄-CuO/C₃N₄-NaClO system achieved 100% removal of dibenzothiophene (DBT) from model fuels, as well as 100% sulfur removal from gasoline and kerosene and 97.7% from diesel fuel. The system was optimized at 30 °C for 5 min using 0.1g of catalyst per 15 mL of fuel at an O/S ratio 1.5. The ODS process followed first-order kinetics, with an activation energy of 27 kJmol^-1. The catalyst maintained high activity over five consecutive cycles, demonstrating excellent recyclability with minimal loss in ODS performance. The enhanced efficiency is attributed to the synergistic interaction among the highly active Mn²⁺/Mn³⁺ and Cu²⁺ species and the NaClO oxidant, which facilitated the rapid oxidation of DBT to dibenzothiophene sulfone (DBTO₂). Thus, the Mn3O4-CuO/C₃N₄-NaClO system represents a potentially cost-effective and environmentally friendly alternative for large-scale oxidative desulfurization of transportation fuels.

The Ru(II) complexes bearing the hydrotris(pyrazolyl)methane ligand (Tpm)─([Ru(κ³-N-Tpm)(NCMe)₃](NO₃)₂ (1), [RuCl(κ³-N-Tpm)(PPh₃)(NCMe)]Cl (2), [Ru(κ³-N-Tpm)(PPh₃)(NCMe)₂](NO₃)₂ (3), [Ru(κ³-N-Tpm)(κ²-N-C₅H₄NCH₂NH₂)(PPh₃)](NO₃)₂ (4), [Ru(κ³-N-Tpm)(κ²-N-NH₂CH₂CH₂NH₂)(PPh₃)](NO₃)₂ (5), and [RuCl(κ³-N-Tpm)(PPh₃)(κ¹-N-NH₂(CH₂)₂OH)]Cl (6))─were evaluated for the azide/alkyne cycloaddition reaction (“click” reaction) in aqueous and organic media. In parallel, and for comparative purposes, piano-stool–Ru(II) complexes featuring cyclopentadienyl and adamantane-like ligands, 1,3,5-triaza-7-phosphaadamantane (PTA) and its N-monomethylated derivative (mPTA = N-methyl-1,3,5-triaza-7-phosphaadamantane) ([RuClCp(PTA)₂] (7), [RuCp(OH₂)(PTA)₂]CF₃SO₃ (8), [RuClCp(mPTA)₂](CF₃SO₃)₂ (9), and [RuCp(OH₂)(mPTA)₂](CF₃SO₃)₃ (10)), were also evaluated for azide–alkyne cycloaddition under similar conditions. Parameters, such as the solvent, substrate concentration, and temperature, were systematically varied to assess their influence on the reaction. The highest conversion rates and selectivity toward the 1,5-disubstituted triazole were achieved in water, acetonitrile/water, and dimethylformamide, while the formation of the 1,4-disubstituted product was slightly favored in methanol. Complexes 3 and 4 exhibited higher regioselectivity and conversion rates in DMF, favoring the formation of the respective 1,5-disubstituted triazole. Complex 3 also catalyzed the cycloaddition of benzyl azide to diphenylacetylene, a representative internal alkyne, reaching a TON of 75 (TOF = 12.5 h^–1). DFT calculations and NMR and TOF-MS spectroscopic studies were conducted to elucidate the mechanism of catalytic cycloaddition between complex 3, phenyl azide, and phenylacetylene under the optimized conditions.

Twelve new mono‐ and polynuclear Cu(II) complexes derived from 3‐(2‐pyridyl)‐5 R ‐1,2,4‐triazoles (HL ⁿ , where R = Me, n = 1; R = Et, n = 2; R = i ‐Pr, n = 3; R = t ‐Bu, n = 4; R = Ph, n = 5; R = Bz, n = 6) containing other ligands, such as nitrate, aqua, or dimethylformamide (dmf), were obtained and structurally characterized. Nine compounds were tested as selective catalysts for the microwave‐assisted oxidation of neat styrene to benzaldehyde (up to 85% yield) via copper‐peroxide reactive species and its further ultrasound‐assisted conversion (up to 99% yield) to the syn ‐ and anti ‐ β ‐nitroethanol mixture with a remarkable diastereoselectivity to the anti‐ isomer.

Air-stable ruthenium( ii ) η ⁶ -arene isocyanide complexes are versatile catalytic precursors for terminal alkyne dimerization/trimerization in aqueous medium.

The chalcogen atom Ch (O, S, Se or Te) replacement at element–Ch⋯nucleophile has a significant impact on the strength and directionality of chalcogen bonding.

Extracting valuable platform chemical from waste biomass is a crucial part of the path to developing a circular, sustainable materials economy. As a particularly significant example, recent developments at the insect biorefinery - utilization of insect biomass - are herein discussed. The focus is placed on the valorization of Hermetia illucens (commonly known as Black Soldier Fly, BSF) waste created during their industrial production process. In particular, pupae exuviae of BSF are used in studies aimed at obtaining useful raw materials, such as chitin and chitosan, for another industry sectors, namely the health industry.

In this work, new copper(I) complexes of borane-functionalized bis(3,5-dimethylpyrazolyl)methane ligands were synthesized, characterized and used as catalysts for the cycloaddition of phenylacetylene and azides. Reaction of the allylated bis(3,5-dimethylpyrazolyl)methane proligand (La) with CuCl or [Cu(NCMe)₄]BF₄ gave rise to the neutral copper chloride complex [(La)CuCl] (1a) or the binuclear cationic copper complex [(La)Cu(NCMe)]₂(BF₄)₂ (2a₂), respectively. The same reactions using a borane-functionalized bis(3,5-dimethylpyrazolyl)methane proligand (Lb) led to the isolation of complexes [(Lb)CuCl] (1b) and [(Lb)Cu(NCMe)₂]BF₄ (2b). The new complexes were characterized by NMR and FTIR spectroscopies, elemental analysis, cyclic voltammetry and, in selected cases, single-crystal X-ray diffraction. Complexes 1a, 1b, 2a₂ and 2b catalyzed the cycloaddition of phenylacetylene and in situ prepared benzyl azide to afford the respective 1,2,3-triazole products. When using complex 0.33 mol% of complex 2b in the presence of 40 equivalents of diisopropylethylamine (DIPEA), a maximum yield of 97% with a maximum TOF value of 800 h⁻¹ was obtained. Complex 2b also catalyzed the cycloaddition of phenylacetylene with 7 azides prepared in situ in 87%–99% yields. The borane-functionalized complexes 1b and 2b were, on average, 4-fold more active than their respective allylated analogues, and complex 2b readily led to the formation of the η²-phenylacetylene complex [(Lb)Cu(η²-PhCCH)]BF₄ (4) and the presumed detection of borane-centered Lewis pairs with MesN₃. These experimental observations, along with computational insights based on DFT calculations, indicated that the respective borane functionalities are beneficial to catalytic activity due to a substrate-directing effect.