Search Results (444)

Pyridinecarbonitriles (pyCN), also referred to as cyanopyridines, are promising ligands for the formation of pyridine-based coordination compounds due to their two different N-donor atoms, which enable versatile coordination modes. Copper(II) complexes containing pyCN derivatives are of particular interest for their potential applications in medicinal chemistry and materials science. In this study, the synthesis, structural characterization, and thermal and magnetic properties of three new copper(II) complexes with 3-pyCN, 4-pyCN, and ethyl picolinimidate, obtained in situ by means of alcoholysis of 2-pyCN, are reported: [Cu₂(μ-Ac)₄(3-pyCN)₂] (1), [Cu(H₂O)₂(Etpic)₂]NO₃ (2), and [Cu(NO₃)₂(CH₃CN)(4-pyCN)₂]·CH₃CN (3). Single-crystal X-ray diffraction confirmed that complex 1 features a dinuclear paddle-wheel structure with bridging acetato ligands and monodentate 3-pyCN molecules, coordinated through the ring nitrogen, while complexes 2 and 3 are mononuclear. Thermal analysis showed an intense and highly exothermic decomposition of complex 3, containing nitrate ligands. Magnetic measurements revealed strong antiferromagnetic coupling in the dinuclear complex 1, whereas complexes 2 and 3 displayed paramagnetic behavior with effective magnetic moments ranging from 1.8 μ_B to 2.0 μ_B, consistent with isolated Cu(II) centers. Full article

The 1:1 stoichiometric reactions of α-amino isobutyric acid (H₂Aib) and diaminosilanes of the type SiRR′(NR¹R²)₂ (SiMe₂(imidazol-1-yl)₂, SiMe₂(NHnPr)₂, and SiRR′(pyrrolidin-1-yl)₂ with R,R′ = Me,Me, Me,H, Me,Vi, and Et,Et) afforded the pentacoordinate silicon complexes (Aib)SiRR′(HNR¹R²) with the release of one equivalent of HNR¹R². Single-crystal X-ray diffraction analyses confirmed the coordination of the N-donor Lewis base (i.e., imidazole, n-propylamine, and pyrrolidine, respectively) in an axial position of the distorted trigonal-bipyramidal Si-coordination sphere, trans to the carboxylate O atom of the Si-chelating Aib-dianion. The N–H moieties of the adduct-forming Lewis bases are involved in N–H⋯O hydrogen bonds with carboxylate groups of adjacent complex molecules, thus supporting the supramolecular structures of these adducts. The equatorially bound NH group of the Aib-dianion is involved in N–H⋯O hydrogen bonds in most cases, and it gives rise to residual dipolar coupling of the ¹⁴N nucleus with its directly bound atoms C and Si, thus causing characteristic shapes of both the ²⁹Si and ¹³C NMR signals of these two atoms in the solid-state spectra. In contrast to the adduct-formation reactions, the analogous conversion of H₂Aib and SiMe₂(NHtBu)₂ did not afford an amine adduct. Instead, a second equivalent of H₂Aib entered the reaction, and the ionic silicon complex [tBuNH₃]⁺[(Aib)₂SiMe]⁻ was obtained and characterized by crystallography and solution NMR spectroscopy. Full article

This review provides a comprehensive overview of recent advances in the synthesis, structural characterization, and applications of Ru(II), Ru(III), and Ru(VI) complexes, which bear tetradentate Schiff bases of salen type. Ruthenium complexes exhibit catalytic, electrochemical, and biological properties, serving as multifunctional platforms that integrate fundamental aspects of coordination chemistry with potential practical applications. Full article

Oxidative stress, driven by excess reactive oxygen species (ROS), is a key factor in the progression of neurodegenerative diseases like Alzheimer’s disease (AD). In this context, copper dysregulation can also contribute to this imbalance, being responsible for enhanced ROS production, so that copper scavenging has been investigated as a possible therapeutic strategy. This study investigates the behavior of two isostructural ligands, featuring an N₃O donor set, that effectively chelate Cu(II) in aqueous solution. Interestingly, their resulting mono- or dinuclear copper complexes feature a coordination environment suitable to foster antioxidant activity. By transforming copper’s oxidant potential into antioxidant action, these systems may reduce copper-induced oxidative damage. The work examines the pH-dependent metal-binding behavior of the ligands, the catalytic properties of the resulting complexes under physiological conditions, and their ability to inhibit β-amyloid peptide aggregation. Full article

This study presents the development of Cu-doped NiMo/TiO₂ photoelectrocatalysts for simultaneous green hydrogen production and pharmaceutical pollutant removal under simulated solar irradiation. The catalysts were synthesized via wet impregnation (15 wt.% total metal loading with 0.6 wt.% Cu) and thermally treated at 400 °C and 900 °C to investigate structural transformations and catalytic performance. Comprehensive characterization (XRD, BET, SEM, XPS) revealed phase transitions, enhanced crystallinity, and redistribution of redox states upon Cu incorporation, particularly the formation of NiTiO₃ and an increase in oxygen vacancies. Crystallite sizes for anatase, rutile, and brookite ranged from 21 to 47 nm at NiMoCu400, while NiMoCu900 exhibited only the rutile phase with 55 nm crystallites. BET analysis showed a surface area of 44.4 m²·g⁻¹ for NiMoCu400, and electrochemical measurements confirmed its higher electrochemically active surface area (ECSA, 2.4 cm²), indicating enhanced surface accessibility. In contrast, NiMoCu900 exhibited a much lower BET surface area (1.4 m²·g⁻¹) and ECSA (1.4 cm²), consistent with its inferior photoelectrocatalytic performance. Compared to previously reported binary NiMo/TiO₂ systems, the ternary NiMoCu/TiO₂ catalysts demonstrated significantly improved hydrogen production activity and more efficient photoelectrochemical degradation of paracetamol. Specifically, NiMoCu400 showed an anodic peak current of 0.24 mA·cm⁻² for paracetamol oxidation, representing a 60% increase over NiMo400 and a cathodic current of −0.46 mA·cm⁻² at −0.1 V vs. RHE under illumination, nearly six times higher than the undoped counterpart (–0.08 mA·cm⁻²). Mott–Schottky analysis further revealed that NiMoCu400 retained n-type behavior, while NiMoCu900 exhibited an unusual inversion to p-type, likely due to Cu migration and rutile-phase-induced realignment of donor states. Despite its higher photosensitivity, NiMoCu900 showed negligible photocurrent, confirming that structural preservation and surface redox activity are critical for photoelectrochemical performance. This work provides mechanistic insight into Cu-mediated photoelectrocatalysis and identifies NiMoCu/TiO₂ as a promising bifunctional platform for integrated solar-driven water treatment and sustainable hydrogen production. Full article

Application of organic ligand 2-(3-ethyl-pyrazin-2-yl)quinoline-4-carboxylate with N/O donor atoms enabled solvothermal synthesis of a 2D Cu(II) coordination polymer, {Cu(L)BF₄}_n (L = deprotonated 2-(3-ethyl-pyrazin-2-yl)quinoline-4-carboxylate). Both the ligand and its coordination polymer have been characterized. The condensed ring system of the applied ligand promotes the formation of coordination polymers rather than mononuclear species. The obtained 2D coordination polymer is photoluminescent with bathochromic/hypsochromic shifts in ligand absorption bands leading to a single absorption band at 465 nm. Density Functional Theory was employed to provide a theoretical description of the possible conformational changes within the ligand, with emphasis on the difference between the ligand conformation in its hydrochloride salt and in the polymer. Two models of polymer fragments were constructed to describe the electronic structure and non-covalent interactions. The Quantum Theory of Atoms in Molecules (QTAIM) was applied for this purpose. Using the obtained results, we were able to develop potential energy profiles for various conformations of the ligand. For the set of the studied systems, we detected non-covalent interactions, which are responsible for the spatial conformation. Concerning the models of polymers, electron spin density distribution has been visualized and discussed. Full article

The structures of hexaammine solvated indium(III) and thallium(III) ions in liquid ammonia solution are determined by EXAFS. Both complexes have regular octahedral coordination geometry with mean In-N and Tl-N bond distances of 2.23(1) and 2.29(2) Å, respectively. Ammine solvated thallium(III) in liquid ammonia is characterized with ²⁰⁵Tl NMR measurements. Solvents such as liquid ammonia, N,N-dimethylthioformamide (DMTF), trialkyl and triphenyl phosphite and phosphine are strong electron pair donors and thereby able to form bonds with a large covalent contribution with strong electron pair acceptors. A survey of reported structures of ammine, DMTF, trialkyl and triphenyl phosphite and phosphine solvated metal ions in the solid state and solution is presented. The M-N and M-S bond distances in ammine and DMTF solvated metal ions are compared with the M-O bond distance in the corresponding metal ion hydrates, expected to form mainly electrostatic interactions with metal ions. The d¹⁰ metal ions have high ability to form bonds with a high degree of covalency with increasing ability down the group and with decreasing charge of the metal ion. The difference in M-N and M-O bond distances between ammine solvated and hydrated metal ions with the same coordination geometry decreases significantly with the increasing ability of the metal ion to form bonds with a large covalent contribution. This difference correlates well with the covalent bonding index, γ_M²*r. Full article

The substrate-induced respiration-inhibition (SIRIN) method has been used to estimate fungi-derived N₂O emissions, but its contribution to soil N₂O emissions remains unclear. There is a need to quantify the fungal fraction of N₂O production more precisely. Here, using isotopocule analysis, we assessed the relative contribution of fungi to soil N₂O production potential under denitrifying conditions, where key limiting factors of denitrification (soil moisture, soil NO₃⁻, and electron donor) were removed. The result showed that the ratio of fungi-derived N₂O emissions (R_F) was 0.83~4.28% in paddy soils, 13.80~23.21% in vineyard soils, and 15.34~65.94% in vegetable field soils, respectively. This indicated that the bacteria were the dominator of soil N₂O production potential in most cases, but fungal pathways could be significant in vegetable field soils. The experiment with bactericide addition showed that inhibitors could affect non-target microorganisms in the SIRIN method. Our further analyses suggest that it is worth to explore the effect of soil organic carbon and microbial synergies on fungi-derived N₂O emissions. Full article

Dye-sensitized solar cells (DSSCs) are promising alternatives for power generation due to their environmental friendliness, cost effectiveness, and strong performance under diffused light. Conversely, their low spectral response in the ultraviolet (UV) region significantly obliterates their overall performance. The so-called luminescent down-shifting (LDS) presents a practical solution by converting high-energy UV photons into visible light that can be efficiently absorbed by sensitizer dyes. Herein, a conventional solid-state technique was applied for the synthesis of an LDS, europium (II)-doped barium orthosilicate (BaSiO₃:Eu²⁺) material. The material exhibited strong UV absorption, with prominent peaks near 400 nm and within the 200–300 nm range, despite a weaker response in the visible region. The estimated optical bandgap was 3.47 eV, making it well-suited for UV absorbers. Analysis of the energy transfer mechanism from the LDS material to the N719 dye sensitizer depicted a strong spectral overlap of $2\times {10}^{10}{\mathrm{M}}^{-1}{\mathrm{c}\mathrm{m}}^{-1}{\mathrm{n}\mathrm{m}}^4$, suggesting efficient energy transfer from the donor to the acceptor. The estimated Förster distance was approximately $6.83\mathrm{n}\mathrm{m}$, which matches the absorption profile of the dye-sensitizer. Our findings demonstrate the potential of BaSiO₃:Eu²⁺ as an effective LDS material for enhancing UV light absorption and improving DSSC performance through increased spectral utilization and reduced UV-induced degradation. Full article

The interaction of cobalt(II) with first-generation quinolones oxolinic acid (Hoxo), flumequine (Hflmq), pipemidic acid (Hppa) and cinoxacin (Hcx) in the presence of the N,N′-donor heterocyclic ligands 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) afforded a series of novel cobalt complexes, namely [Co(bipy)₂(oxo)](PF₆)₂·H₂O (1), [Co(phen)₂(oxo)](PF₆)₂·0.5CH₃OH·0.5H₂O (2), [Co(bipy)₂(flmq)](PF₆)₂·0.5CH₃OH·0.5H₂O (3), [Co(bipy)₂(ppa)](PF₆)₂·CH₃OH·0.5H₂O (4), [Co(phen)₂(cx)](PF₆)₂·CH₃OH·0.5H₂O (5), and [Co(phen)₂(flmq)](PF₆)·0.5CH₃OH·H₂O (6). The characterization of the complexes involved physicochemical techniques, various spectroscopies and single-crystal X-ray crystallography. The affinity of complexes to calf-thymus (CT) DNA was monitored with various techniques, suggesting intercalation in-between the DNA-nucleobases as the most probable interaction mode, which may be combined with electrostatic interactions as a result of the cationic nature of the complexes. The affinity of the complexes for bovine and human serum albumin proteins was monitored, and the determined corresponding albumin-binding constants revealed a tight and reversible interaction. Full article

A nitro-derivative of fenamic acid (4′–nitro–fenamic acid) was synthesized and used as ligand for the synthesis of four Co(II) complexes in the absence or presence of the N,N′-donors 2,2′–bipyridylamine, 1,10–phenanthroline and 2,9–dimethyl–1,10–phenanthroline. The characterization of the resultant complexes was performed with diverse techniques (elemental analysis, molar conductivity measurements, IR and UV-vis spectroscopy, single-crystal X-ray crystallography). The biological evaluation of the compounds encompassed (i) antioxidant activity via hydrogen peroxide (H₂O₂) reduction and free radical scavenging; (ii) antimicrobial screening against two Gram-positive and two Gram-negative bacterial strains; (iii) interactions with calf-thymus (CT) DNA; (iv) cleavage of supercoiled pBR322 plasmid DNA (pDNA), in the dark or under UVA/UVB/visible light irradiation; and (v) binding affinity towards bovine and human serum albumins. The antioxidant activity of the compounds against 2,2′–azinobis–(3–ethylbenzothiazoline–6–sulfonic acid) radicals and H₂O₂ is significant, especially in the case of H₂O₂. The complexes exhibit adequate antimicrobial activity against the strains tested. The complexes interact with CT DNA through intercalation with binding constants reaching a magnitude of 10⁶ M⁻¹. The compounds have a significantly enhanced pDNA-cleavage ability under irradiation, showing promising potential as photodynamic therapeutic agents. All compounds can bind tightly and reversibly to both albumins tested. Full article

This study presents a cost-effective and feasible technique for the deep denitrification of wastewater, based on sulfur autotrophic denitrification mediated by polysulfides (${\mathrm{S}}_{\mathrm{n}}^{2-}$). Various polysulfides were used as electron donors in an aerobic/anoxic sequencing batch reactor (SBR) to simulate nitrification and denitrification processes. The performance of different polysulfide species and their respective dosages were evaluated to determine the optimal conditions for nitrogen removal. Under optimal nitrogen removal conditions with a dosing of 19.2 mg S/L from Na₂S₃, the system was operated continuously for 38 days, with low sludge production during the process. During stable operation, the system achieved an average removal of 7.3 mg/L of $\mathrm{N}{\mathrm{O}}_3^{-}\text{-}\mathrm{N}$, corresponding to a removal efficiency of 23.1%. No significant accumulation of $\mathrm{N}{\mathrm{O}}_2^{-}\text{-}\mathrm{N}$ was observed in the effluent, and the average utilization efficiency of Na₂S₃ reached 83.7%. Continuous dosing of Na₂S₃ promoted the enrichment of sulfur autotrophic denitrification-related microorganisms within the system. Full article

Photodynamic therapy (PDT) is a minimally invasive technique—used for the local eradication of neoplastic cells—that exploits the interaction of light, oxygen, and a photo-responsive drug called photosensitizer (PS) for the local generation of lethal ROS. Push-pull chromophores, that bear electron donor (D) and acceptor (A) groups linked through a π-electron bridge, are characterized by a non-homogeneous charge distribution in their excited state, with charge transfer from one extremity of the chain to the other one (Internal Charge Transfer—ICT). This phenomenon has a direct impact on the photophysical features of the push-pull compounds, as the bathochromic shift of the emission maxima and intersystem crossing (ISC) of the excited state are directly connected with the production of reactive oxygen species (ROS). In continuing our research regarding the synthesis and use of oligophenylene ethynylenes (OPEs) in PDT, two new push-pull glycosyl OPE-NOF and OPE-ONF—featuring electron-donor N,N-dimethylamino (N) and dimetoxyaryl (O) and acceptor tetrafluoroaryl (F) moieties on the OPE chain—have been efficiently prepared. The interchanged position of the D groups onto the conjugated skeleton was aimed to tune and optimize the push-pull effect, while the introduction of glucoside terminations was directed to give biocompatibility and bioaffinity to the chromophores. OPE-NOF, OPE-ONF, and the synthetic intermediates were fully characterized, and their photophysical properties were investigated by using UV-Vis absorption and emission spectroscopy. OPE-NOF showed a strong charge-transfer character and high PDT effect on HeLa cancer cells when irradiated with non-harmful blue light, causing massive cancer cell death. Full article

This research aimed to co-produce CQDs and hydrochar from natural sources to improve the photocatalytic properties of TiO₂. Juice extract from Citrus lemon fruits from south-eastern Spain was used as the carbon precursor. The synthesis strategy of the CQDs and hydrochar (Hc) was divided into different stages aimed at figuring out the role of the temperature (180, 220, 250 °C), the addition of TiO₂ nanoparticles, and the presence of N-/P-donor compounds (ethylenediamine and orto-phosphoric acid) in the photocatalytic properties of final composites. The results revealed that at 250 °C, using agro-carbon materials as Hc, and the addition of N-donor compounds, improved the photocatalytic activity and photodegradation rate of TiO₂ over methyl orange (MO) under blue light by 1000% and 2700%, respectively, with the parallel reduction of TiO₂ bandgap from 3.5 eV (Uv light) to 3.00 eV (visible light). These results are related to the ability of the carbon materials (electronegative) to enhance the formation of a Ti³⁺-active state. This study provides a landscape for a one-step method for the production of agro-carbon/TiO₂ photocatalysts with high activity under visible light as an efficient and sustainable strategy for applications such as energy generation and water purification under sunlight. Full article

A zinc complex bearing a pyrazolone-based azomethine ligand has been synthesized for blue-emitting organic light-emitting diodes (OLEDs). The azomethine ligand H₂L and the complex [ZnL·H₂O] were characterized by IR, 1H NMR, XRD, and TGA/DSC techniques. According to a single-crystal X-ray diffraction analysis, the complex [ZnL·H₂O] has a molecular structure. Its solid-state PL maxima appear to be at 416 nm and emit moderate blue emission with a quantum yield (QY) of 2%, with a dehydrated form of the complex showing greater efficiency with a QY of 55.5%. ZnL-based electroluminescent devices for OLED applications were fabricated. The devices exhibit blue emission with brightness up to 5300 Cd/A. Full article