Abstract Tryptophan (Trp) oxidation is a key biochemical process influencing plant development and numerous biomedical pathways. Here, we investigate how manganese doping modulates the catalytic behavior of titanium dioxide nanoparticles toward selective Trp oxidation. Mn-doped TiO2 nanoparticles containing 5%, 10%, and 20% Mn were systematically examined, while structurally related metal oxides (pristine TiO2, MnO2, MnFe2O4, maghemite (γ-Fe2O3), and industrial Fe3O4) were included as reference materials to establish catalytic benchmarks. Whereas the reference oxides predominantly promoted nonspecific reactive oxygen species (ROS) generation or exhibited lower catalytic efficiency, Mn-doped TiO2 displayed highly tunable reactivity. Specifically, 5% Mn doping favored broad-spectrum photocatalytic ROS production, whereas increasing the Mn content to 20% transformed the material from a conventional photocatalyst into a highly selective nanozyme. The 20% Mn-doped TiO2 exhibited superior biomimetic catalytic activity and was therefore subjected to detailed mechanistic studies. Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) revealed highly selective, nanozyme-driven Trp oxidation pathways leading to the formation of auxin-mimicking metabolites. In vivo experiments using Arabidopsis thaliana demonstrated that the resulting metabolite cocktail significantly stimulated lateral root formation, indicating improved nutrient acquisition potential. Collectively, these findings establish Mn-doped TiO2 as a tunable catalytic platform capable of directing amino acid oxidation toward biologically relevant products and highlight its potential applications in agriculture and biomedicine.

This study assesses density functional theory (DFT) methods for their accuracy in calculating hyperfine coupling constants (HFCCs) of heavy heteroatom radicals with heteroatoms including Sb, Bi, In, Tl and Sn. Given the essential role of EPR spectroscopy in characterization of these species, it is crucial that theoretical models can predict HFCCs accurately for heavy elements. This work presents a computational approach that addresses crucial factors: selection of basis set, hybrid exchange‐correlation functional, higher Hartree‐Fock exchange and the Gaussian description of nuclear charge. The relativistic effects were introduced using one‐component linear response theory with the second‐order Douglas–Kroll–Hess (DKH2) formalism and the fully relativistic four‐component Dirac–Kohn–Sham (DKS) method. Our findings show that, while one‐component DFT is accurate for the 4th row elements, the four‐component method is more precise for the 5th row radicals and the one‐component approach fails for the 6th row congeners. Increasing HF exchange significantly improves HFCC predictions. The developed framework for accurate HFCC calculations will enhance the understanding of electronic and magnetic properties of heavy element radicals and can be used by computational chemists and experimentalists alike.

This study comprehensively analyses two new ruthenium(III) complexes, [RuIIICl4(Nic)2]-[(CH3)2NH2]+DMF, 1, and [RuIIICl2(3-HPA)2]-[3-HH2PA]+(EtOH)2, 2, (where Nic = nicotinic acid (vitamin B3), 3-HPA = anion of a 3-hydroxypicolinic acid), as potential antimicrobial agents, highlighting their physicochemical properties, nanoparticle formation, and cytotoxic activity. The complexes were fully characterised by a single crystal X-ray diffraction technique, Fourier-transform infrared, energy-dispersive X-ray, and electron paramagnetic resonance spectroscopies. The synthesis of micro- and nanoparticles (NPs) of these complexes was performed using the liquid anti-solvent crystallisation method. The formation of NPs was confirmed, and their sizes were determined using scanning electron microscopy and dynamic light scattering techniques. The Debye-Scherrer technique, based on powder diffraction X-ray data, indicated the high crystallinity of the nanomaterials. Toxicity and morphological effects on L929 fibroblasts, hepatocellular carcinoma (Hep-G2) and human epithelial colorectal adenocarcinoma (Caco-2) cell lines of the complexes were assessed using the MTT assay and an inverted phase-contrast microscope, respectively. Complex 1 is a promising anti-cancer drug candidate targeting intestinal cancers, showing cytotoxicity against Caco-2 cancer cells and no cytotoxicity against L929 fibroblast cells, while complex 2 is markedly cytotoxic. The antibacterial activity of the complexes was assessed against methicillin-resistant Staphylococcus aureus (MRSA) and Klebsiella pneumoniae strains using the minimum inhibitory concentration (MIC) method. Complex 2 demonstrates superior bactericidal properties, achieving MIC values as low as 125 μg ml-1 for S. aureus, while complex 1 exhibits lower antimicrobial efficacy. The role of ligand composition in modulating bioactivity was examined.

The new heterometallic compounds, {[Ni(tren)(H2O)]2(mu 1,3-NCS)}[Cr(NCS)6] (1), {[Cu(tren)(H2O)]2(mu 1,3-NCS)} [Cr(NCS)6] (2) and [Ni(tren)(H2O)(NCS)][Cr(NCS)4(NH3)2] (3) (tren = tris(2-aminoethylo)amine), were obtained and characterized by X-ray analysis, IR spectra, XAS and magnetic measurements. The compounds 1 and 2 were isomorphous and crystallized in the monoclinic P21/c space group. These compounds consisted of a homometallic Ni-Ni and Cu-Cu dimers in 1 and 2, respectively, in which metal ions were coordinated by a single thiocyanate mu 1,3-NCS- bridge, and the [Cr(NCS)6]3- unit as the counterion. Crystal lattice of compound 3 had an orthorhombic Pbca symmetry. Single monomeric nickel ions and [Cr(NCS)4(NH3)2]- ions were arranged in the form of columns composed of alternately arranged complex cations and anions stabilised by hydrogen bonding. The XAS spectra on the selected 3d metals (Ni, Cu, Cr) L-edge and the N and O K-edge were intended to enable the determination of the spin state and configuration of Ni, Cu, Cr and to relate this information to other properties of materials, such as local symmetry of central atoms, charge state, covalency of unoccupied valence orbitals. The K-edge and L-edge XAS spectra confirmed the elemental composition and local geometry of transition metals occurring in newly synthesized molecular materials. Similarities in topology, local symmetry and structure enabled significant simplification of the magnetic properties modelling by assuming magnetic coupling inside {NiIINiII} or {CuIICuII} binuclear units separated by paramagnetic [Cr(NCS)6]3- units in 1 and 2. The obtained results indicated dominant antiferromagnetic interactions between metal ions in the dimers, which was confirmed by theoretical DFT and ab initio CASSCF/NEVPT2 calculations.

This study assesses density functional theory (DFT) methods for their accuracy in calculating hyperfine coupling constants (HFCCs) of heavy heteroatom radicals with heteroatoms including Sb, Bi, In, Tl, and Sn. Given the essential role of electron paramagnetic resonance spectroscopy in characterization of these species, it is crucial that theoretical models can predict HFCCs accurately for heavy elements. This work presents a computational approach that addresses crucial factors: selection of basis set, hybrid exchange-correlation functional, higher Hartree-Fock (HF) exchange, and the Gaussian description of nuclear charge. The relativistic effects are introduced using one-component linear response theory with the second-order Douglas-Kroll-Hess formalism and the fully relativistic four-component Dirac-Kohn-Sham method. The findings show that, while one-component DFT is accurate for the 4th-row elements, the four-component method is more precise for the 5th-row radicals and the one-component approach fails for the 6th-row congeners. Increasing HF exchange significantly improves HFCC predictions. The developed framework for accurate HFCC calculations will enhance the understanding of electronic and magnetic properties of heavy element radicals and can be used by computational chemists and experimentalists alike.

This study reports the synthesis, characterization, and biological evaluation of four novel heteronuclear Ru(II)-Cu(II) complexes with phosphine-fluoroquinolone conjugates. Structural analysis using X-ray diffraction, density functional theory calculations, and various spectroscopic techniques confirmed the stability and coordination geometries. The cytotoxicity was evaluated in vitro across multiple cancer cell lines (lung, breast, pancreatic, prostate) and noncancerous cells. In vivo toxicity was also assessed using a zebrafish (Danio rerio) larvae model. The results demonstrated that Ru(II)-Cu(II) complexes exhibit greater anticancer activity compared with cisplatin while almost being nontoxic toward control cells in vitro. Mechanistic studies revealed that their action involves nuclei accumulation, reactive oxygen species generation, lipid peroxidation, and mitochondrial membrane depolarization. The expression ratio of Bax to Bcl-2 mRNA correlates with apoptotic cell death. Additionally, encapsulation of the one Ru(II)-Cu(II) complex in bilosomes significantly improved its stability, selectivity, and therapeutic efficacy in three-dimensional (3D) cancer spheroid models.

The redox reactions of a pyrazine-bridged binuclear [(edta)RuIIIpzRuIII(edta)]2− (edta4− = ethylenediaminetetraacetate; pz = pyrazine) have been investigated spectrochemically and spectroelectrochemically for the first time.

Two dinuclear copper(II) complexes with macrocyclic Schiff bases K1 and K2 were prepared by the template reaction of (R)-(+)-1,1′-binaphthalene-2,2′-diamine and 2-hydroxy-5-methyl-1,3-benzenedicarboxaldehyde K1, or 4-tert-butyl-2,6-diformylphenol K2 with copper(II) chloride dihydrate. The compounds were characterized by spectroscopic methods. X-ray crystal structure determination and DFT calculations confirmed their geometry in solution and in the solid phase. Moreover, intermolecular interactions in the crystal structure of K2 were analyzed using 3D Hirshfeld surfaces and the related 2D fingerprint plots. The magnetic study revealed very strong antiferromagnetic CuII-CuII exchange interactions, which were supported by magneto-structural correlation and DFT calculations conducted within a broken symmetry (BS) framework. Complexes K1 and K2 exhibited luminescent properties that may be of great importance in the search for new OLEDs. Both K1 and K2 complexes showed emissions in the range of 392–424 nm in solutions at various polarities. Thin materials of the studied compounds were deposited on Si(111) by the spin-coating method or by thermal vapor deposition and studied by scanning electron microscopy (SEM/EDS), atomic force microscopy (AFM), and fluorescence spectroscopy. The thermally deposited K1 and K2 materials showed high fluorescence intensity in the range of 318–531 nm for K1/Si and 326–472 nm for the K2/Si material, indicating that they could be used in optical devices.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The COVID-19 pandemic has had a devastating impact on global health, highlighting the need to understand how the SARS-CoV-2 virus damages the lungs in order to develop effective treatments. Recent research has shown that patients with COVID-19 experience severe oxidative damage to various biomolecules. We propose that the overproduction of reactive oxygen species (ROS) in SARS-CoV-2 infection involves an interaction between copper ions and the virus's spike protein. We tested two peptide fragments, Ac-ELDKYFKNH-NH2 (L1) and Ac-WSHPQFEK-NH2 (L2), derived from the spike protein of the Wuhan strain and the beta variant, respectively, and found that they bind Cu(II) ions and form a three-nitrogen complexes at lung pH. Our research demonstrates that these complexes trigger the overproduction of ROS, which can break both DNA strands and transform DNA into its linear form. Using A549cells, we demonstrated that ROS overproduction occurs in the mitochondria, not in the cytoplasm. Our findings highlight the importance of the interaction between copper ions and the virus's spike protein in the development of lung damage and may aid in the development of therapeutic procedures.

Surfactin, a group of cyclic lipopeptides produced by Bacillus subtilis, possesses surfactant properties and is a promising natural and biologically active compound. In this study, we present a comprehensive characterization of surfactin, including its production, chromatographic separation into pure homologues (C-12, C-13, C-14, C-15), and investigation of their physicochemical properties. We determined adsorption isotherms and interpreted them using the Gibbs adsorption equation, revealing that the C-15 homologue exhibited the strongest surface tension reduction (27.5 mN/m), while surface activity decreased with decreasing carbon chain length (32.2 mN/m for C-12). Critical micelle concentration (CMC) were also determined, showing a decrease in CMC values from 0.35 mM for C-12 to 0.08 mM for C-15. We employed dynamic light scattering (DLS), transmission electron microscopy (TEM), and density functional theory (DFT) calculations to estimate the size of micellar aggregates, which increased with longer carbon chains, ranging from 4.7 nm for C-12 to 5.7 nm for C-15. Furthermore, aggregation numbers were determined, revealing the number of molecules in a micelle. Contact angles and emulsification indexes (E-24) were measured to assess the functional properties of the homologues, showing that wettability increased with chain length up to C-14, which is intriguing as C-14 is the most abundant homologue. Our findings highlight the relationship between the structure and properties of surfactin, providing valuable insights for understanding its biological significance and potential applications in various industries. Moreover, the methodology developed in this study can be readily applied to other cyclic lipopeptides, facilitating a better understanding of their structure-properties relationship.

The phosphine ligand (Ph2PCH2N(CH3)(CH2)(2)Ph, PNMPEA) obtained by the reaction of the (hydroxymethyl)diphenylphosphine with naturally occurring alkaloid N-methylphenethylamine, was used to synthesize the half-sandwich iridium(III) (Ir(eta 5-Cp*)Cl2Ph2PCH2N(CH3)(CH2)(2)Ph, IrPNMPEA) and ruthenium(II) (Ru(eta 6-p-cymene)Cl2Ph2PCH2N(CH3)(CH2)(2)Ph, RuPNMPEA) complexes. They were characterized using a vast array of methods, including 1D and 2D NMR, ESI(+)MS spectrometry, elemental analysis, cyclic voltammetry (CV), electron spectroscopy in the UV-Vis range (absorption, fluorescence) and density functional theory (DFT). The initial antimicrobial activity in vitro toward Gram-positive and Gram-negative bacterial strains was examined, indicating that both complexes are selective towards Gram-positive bacteria, e. g., Staphylococcus aureus, where the IrPNMPEA has been more bactericidal compared to RuPNMPEA. Additionally, the interactions of these compounds with various biomolecules, such as DNA (ctDNA, plasmid DNA, 9-ethylguanine (9-EtG), and 9-methyladenine (9-MeA)), nicotinamide adenine dinucleotide (NADH), glutathione (GSH), and ascorbic acid (Asc) were described. The results showed that both Ir(III) and Ru(II) complexes accelerate the oxidation process of NADH, GSH and Asc that appeared to occur by an electron transfer mechanism. Interestingly, only IrPNMPEA leads to the formation of various biomolecule adducts, which can explain its higher activity. Furthermore, RuPNMPEA and IrPNMPEA have been interacting with the DNA through weak noncovalent interactions.

We report the synthesis and structural, spectroscopic and magnetic properties of new 1D coordination polymeric complex {[Cu( μ- l- Arg) 2 ]SO 4 ⋅1.5H 2 O} n ( 1 ) that contains asymmetric μ −O,O’ carboxylic bridge linking distorted square-pyramidal [Cu( μ- l- Arg) 2 ] 2+ coordination units. In 1D, the syn − anti − μ 2 − η 1 : η 1 zigzag polymer conformation, the adjacent Cu(II) ions are distanced by 5.707 Å, and the subsequent Cu∙∙∙Cu proximity in 1D-coordination chain equals 6.978 Å. Detailed interpretation of IR and Raman spectra of l- arginine and 1 was performed. The principal components of the g tensor determined from EPR experiments ( g x = 2.059, g y = 2.075, g z = 2.228) indicate nearly axial symmetry of Cu(II) coordination sphere and correspond to the unpaired electron occupying the d x 2– y 2 orbital. The single broad band at 16,200 cm –1 , characteristic of d−d transition, is assigned to the dominant dublet-dublet 2 B 1 g ( d x 2– y 2 )→ 2 E g ( d yz≈ d xz ) transition. Magnetic susceptibility measurements have revealed ferromagnetic coupling between the Cu(II) ions within the 1D-coordination chain, while the intermolecular coupling is antiferromagnetic. Graphical Abstract

The exchange coupling, represented by the J parameter, is of tremendous importance in understanding the reactivity and magnetic behavior of open-shell molecular systems. In the past, it was the subject of theoretical investigations, but these studies are mostly limited to the interaction between metallic centers. The exchange coupling between paramagnetic metal ions and radical ligands has hitherto received scant attention in theoretical studies, and thus the understanding of the factors governing this interaction is lacking. In this paper, we use DFT, CASSCF, CASSCF/NEVPT2, and DDCI3 methods to provide insight into exchange interaction in semiquinonato copper(II) complexes. Our primary objective is to identify structural features that affect this magnetic interaction. We demonstrate that the magnetic character of Cu(II)-semiquinone complexes are mainly determined by the relative position of the semiquinone ligand to the Cu(II) ion. The results can support the experimental interpretation of magnetic data for similar systems and can be used for the in-silico design of magnetic complexes with radical ligands.

A new organic-inorganic hybrid, AZEMnBr, has been synthesized and characterized. The thermal differential scanning calorimetry, differentialthermal analysis, and thermogravimetric analyses indicate one structural phasetransition (PT) at 346 and 349 K, on cooling and heating, respectively.AZEMnBrcrystallizes at 365 K in the orthorhombic,Pnma, structure, which transforms tomonoclinicP21/nat 200 K. Due to the X-ray diffraction studies, the anionicMnBr42-moiety is discrete. The azetidinium cations show dynamical disorder inthe high-temperature phase. In the proposed structural PT, the mechanism isclassified as an order-disorder type. The structural changes affect the dielectricresponse. In this paper, the multiple switches between low- and high- dielectricstates are presented. In addition, it was also observed that the crystal possesses amutation offluorescent properties between phase ON and OFF in the PT's pointvicinity. We also demonstrate that EPR spectroscopy effectively detects PTs instructurally diverse Mn(II) complexes.AZEMnBrcompounds show DC magnetic data consistent with theS= 5/2 spin system withsmall zero-field splitting, which was confirmed by EPR measurements and slow magnetic relaxation under the moderate DCmagneticfield typical for a single-ion magnet behavior. Given the above, this organic-inorganic hybrid can be considered a rareexample of multifunctional materials that exhibit dielectric, optical, and magnetic activity

Four hexanuclear chloride and sulphate Ni(II) and Cu(II) complexes 1, 2, 4 and 5 and one tetranuclear nitrate Cu(II) complex 3 have been synthesised from appropriate metal salts and 6 + 6 octadecaaza macrocyclic ligands. All obtained coordination compounds have been characterised by elemental analysis, spectroscopic methods (ESI MS, NMR and EPR), magnetic susceptibility measurements and X-ray crystallography. Their X-ray crystal structures reveal different coordination modes of metal cations involved in the obtained centro-symmetrical coordination compounds. The conformational folding of the macrocyclic ligand adopted in the respective complexes depends on the number of metal cations bound within the macrocycle but not on their type. The cavities of these multinuclear complexes might be occupied by solvent molecules and counter anions bound by hydrogen bonds or might be empty in the case where the macrocyclic ring of the ligand is squeezed in the middle. All obtained Ni(II) and Cu(II) coordination compounds are paramagnetic. This has been proved by their 1H NMR and EPR spectra and magnetic measurements. Direct current (DC) variable-temperature magnetic susceptibility measurements on the polycrystalline samples of 1-5 were carried out in the temperature range of 1.8-300 K. The magnetic behaviour of 1 and 2 is dominated by the magnetic anisotropy of the nickel(II) ion masking the magnetic interactions between magnetic centres. The magnetic data of 3-5 reveal small antiferromagnetic interactions within the Cu4 and Cu6 units. EPR experiments for 3-5 show, at 9.6 and 34 GHz frequencies, that the predominant contribution to the orbitals occupied by the unpaired electrons in the ground state originates from dx2-y2.

Two new ion-pair complexes, consisting of a cationic polypirydyl Ru(II) complex ([Ru-II(terpy)(bipy)Cl](+) or [RuII(terpy)(phen)Cl](+)) and the cis-[RuIIICl2(pic)(2)](-) anion (terpy = 2,2 ':6 ',2 ''-terpyridine, bipy = 2,2 '-bipyr-idine, phen = 1,10-phenanthroline and pic- = picolinate) were synthesized. Magnetic and EPR studies were preceded by identifying the obtained species and checking the homogeneity and purity of the bulk material using various analytical techniques: single-crystal and powder X-ray diffraction, SEM, EDX, and FT-IR spectroscopies in the solid state, and ESI-MS in solution. The spectral characteristics in the UV-vis range and redox behavior of the ion-pair complexes were examined. The principal g components for [RuII(terpy)(bipy)Cl](+)[cis-(RuCl2)-Cl-III(- pic)(2)](-) .(CH3)(2)CO.H2O,1, and [RuII(terpy)(phen)Cl]+[cis-(RuCl2)-Cl-III(pic)(2)](-) .2H(2)O, 2, and their Ru(III )precursor [H (Hpic)(2)](+)[cis-(RuCl2)-Cl-III(pic)(2)](-)center dot 2H(2)O were similar and typical for low-spin d5 species. The presence of one un-paired electron (in the dxy orbital) was shown by DFT calculations. The EPR spectra of 1 and 2 were characteristic for species in a singlet state (S = 1/2 systems) in contrast to that of their analog, previously reported for the first Ru-II/Ru(III )ion-pair complex, [RuII(bipy)2(pic)](+)[cis-(RuCl2)-Cl-III(pic)2]-, typical for a species in the triplet state (S = 1 system).

Copper ions bind to biomolecules (e.g., peptides and proteins) playing an essential role in many biological and physiological pathways in the human body. The resulting complexes may contribute to the initiation of neurodegenerative diseases, cancer, and bacterial and viral diseases, or act as therapeutics. Some compounds can chemically damage biological macromolecules and initiate the development of pathogenic states. Conversely, a number of these compounds may have antibacterial, antiviral, and even anticancer properties. One of the most significant current discussions in Cu biochemistry relates to the mechanisms of the positive and negative actions of Cu ions based on the generation of reactive oxygen species, including radicals that can interact with DNA molecules. This review aims to analyze various peptide–copper complexes and the mechanism of their action.

Surfactants are molecules that lower surface or interfacial tension, and thus they are broadly used as detergents, wetting agents, emulsifiers, foaming agents, or dispersants. However, for modern applications, substances that can perform more than one function are desired. In this study we evaluated antioxidant properties of two homological series of N-oxide surfactants: monocephalic 3-(alkanoylamino)propyldimethylamine-N-oxides and dicephalic N,N-bis[3,3′-(dimethylamino)propyl]alkylamide di-N-oxides. Their antiradical properties were tested against stable radicals using electron paramagnetic resonance (EPR) and UV-vis spectroscopy. The experimental investigation was supported by theoretical density functional theory (DFT) and ab initio modeling of the X–H bonds dissociation enthalpies, ionization potentials, and Gibbs free energies for radical scavenging reactions. The evaluation was supplemented with a study of biological activity. We found that the mono- and di-N-oxides are capable of scavenging reactive radicals; however, the dicephalic surfactants are more efficient than their linear analogues.