A series of six new heteroleptic copper(I) complexes of the [Cu(N^N)(P^P)]+ type are reported in which P^P is 4,5-bis(diphenylphosphano)-9,9-dimethylxanthene (xantphos) and N^N are ligands based on 1,10-phenanthroline (phen) with different degrees of steric encumbrance in their 2,9-positions (R = H or CH3), and varying substitution on their imidazo backbone. The synthesized complexes were fully characterized by NMR spectroscopy, high-resolution mass spectrometry, as well as elemental and single-crystal X-ray analysis. Their electrochemical and photophysical properties were investigated, including supporting theoretical calculations, and HER catalytic investigations were conducted to probe potential reactivity. While the luminescence properties vary across the series in dichloromethane (DCM) and tetrahydrofuran (THF) solvents, selected complexes act as strong emitters, achieving photoluminescence quantum yields of up to 47%. In particular, [Cu(L3b)(xantphos)]PF6 exhibits a long emission lifetime of 8.52 μs in THF.

Heteroleptic copper(I) complexes with the general formula [Cu(N^N)(P^P)]X constitute one of the most studied categories of 3d metal photosensitizers. Here, we examine using 1,2,4,5-tetrazine-based ligands to synthesize photoactive Cu(I) complexes. The newly prepared complexes were characterized by single-crystal X-ray analysis, which revealed the formation of dinuclear complexes [Cu2(μ-L1)(xantphos)2](ClO4)2 (1) and [Cu2(μ-L2)(xantphos)2](ClO4)2 (2), and mononuclear complexes [Cu(L3)(xantphos)]ClO4 (3) and [Cu(L4)(xantphos)]ClO4 (4), where L1 = 3,6-di(2'-pyridyl)-1,2,4,5-tetrazine (bptz), L2 = 3,6-bis-(3,5-dimethyl-pyrazol-1-yl)-1,2,4,5-tetrazine, L3 = 3-(2-pyridyl)-1,2,4,5-tetrazine, L4 = 3-(3,5-dimethyl-1H-pyrazol-1-yl)-1,2,4,5-tetrazine and xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene. Solution stability assays were addressed by NMR spectroscopy showing that complexes are stable in dichloromethane over several days. The electronic excited states were investigated by UV-Vis and luminiscence spectroscopy and interpreted with the help of TD-DFT calculations. In the case of all the newly prepared complexes 1-4, the absorptions in the visible region were assigned to non-emissive MLCT transitions between the Cu(I) and the respective tetrazine ligand. Redox properties were probed by cyclic voltammetry and also supplemented by DFT calculations. Interestingly, tetrazine ligands L1-L4 show a shift of reduction potential to less negative values upon the formation of Cu(I) complexes 1-4. Moreover, the two complexes 3-4 represent the first reported case of mononuclear heteroleptic Cu(I)-tetrazine complexes.

The copper(II), cobalt(II), and zinc(II) complexes with 2-(1H-benzimidazol-2-ylmethylsulfanylmethyl)-1H-benzimidazole (tbb) and 2-[2-[2-(1H-benzimidazol-2-yl)ethylsulfanyl]ethyl]-1H-benzimidazole (tebb), [Cu(tbb)Cl2] (1), [Co(tbb)Cl2] (2), [Zn(tbb)Cl2] (3), [Cu(tebb)Cl(H2O)]Cl (4), [Co(tebb)Cl2]n·nCH3OH (5) and [Zn(tebb)Cl(H2O)]Cl (6), have been prepared and evaluated for antiproliferative activity. The structure of (4) was proved by X-ray diffraction crystallography. The coordination compounds were tested for their cytotoxic activities in cancer cell lines in vitro. The lower IC50 values were obtained for Co(II), Cu(II), and Zn(II) complexes with tebb in comparison with tbb complexes. Complex 2 showed strong antiproliferative selectivity for leukemia CEM cells and nontoxicity towards other tested cell lines and normal human cells (BJ and RPE-1). Proapoptotic activity of 2 and 5 were weaker than positive control cisplatin, but the big advantage of these complexes was their zero-cytotoxicity for normal healthy cells in contrast to the high cytotoxicity of cisplatin. The activation of apoptotic initiation phase was detected in neuroblastoma cancer cell line SH-SY5Y where 5 was cytotoxic without fragmentation of cells. Interestingly, complexes 5, 6, and tebb, together with cisplatin, dramatically impaired the mitochondrial membrane potential of SH-SY5Y after 72 h. Taken together, we demonstrated that our compounds trigger apoptosis via the mitochondrial pathway.

Three nickel, copper, and zinc complexes with dicarboxylic acids (3,3′-dithiodipropionic acid (H2dtdp) and fumaric acid (H2fu)) and N-donor ligands (1,10-phenanthroline (phen), N′–methyldipropylenetriamine (mdpta), and N,N,N′,N″,N″-pentamethyldiethylenetriamine (pmdien)) were synthesized. These complexes were characterized using elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. Interestingly, [Ni(dtdp)(phen)(H2O)3]∙0.5H2O (1) is a mononuclear complex, where the dtdp dianion employs only one carboxylate group for coordination to the central nickel atom. [(ClO4)(mdpta)Cu(μ-dtdp)Cu(mdpta)(H2O)](ClO4) (2) is a dinuclear copper complex with a dtdp bridge and different coordination on the copper center. [{Zn(pmdien)(H2O)}2(μ-fu)](ClO4)2 (3) is a symmetric dimer with a bridging fumarate ligand. These coordination compounds were tested for their antibacterial activities on Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis bacteria strains. All the complexes show moderate activities on the mentioned strains.

Direct selective transformation of greenhouse methane (CH4 ) to liquid oxygenates (methanol) can substitute energy-intensive two-step (reforming/Fischer-Tropsch) synthesis while creating environmental benefits. The development of inexpensive, selective, and robust catalysts that enable room temperature conversion will decide the future of this technology. Single-atom catalysts (SACs) with isolated active centers embedded in support have displayed significant promises in catalysis to drive challenging reactions. Herein, high-density Ni single atoms are developed and stabilized on carbon nitride (NiCN) via thermal condensation of preorganized Ni-coordinated melem units. The physicochemical characterization of NiCN with various analytical techniques including HAADF-STEM and X-ray absorption fine structure (XAFS) validate the successful formation of Ni single atoms coordinated to the heptazine-constituted CN network. The presence of uniform catalytic sites improved visible absorption and carrier separation in densely populated NiCN SAC resulting in 100% selective photoconversion of (CH4 ) to methanol using H2 O2 as an oxidant. The superior catalytic activity can be attributed to the generation of high oxidation (NiIII ═O) sites and selective C─H bond cleavage to generate •CH3 radicals on Ni centers, which can combine with •OH radicals to generate CH3 OH.

Background The emergence of antibiotic resistance in pathogenic bacteria has become a global threat, encouraging the adoption of efficient and effective alternatives to conventional antibiotics and promoting their use as replacements. Titanium dioxide nanoparticles (TiO 2 NPs) have been reported to exhibit antibacterial properties. In this study, we synthesized and characterized TiO 2 NPs in anatase and rutile forms with surface modification by geraniol (GER). Results The crystallinity and morphology of modified TiO 2 NPs were analyzed by UV/Vis spectrophotometry, X-ray powder diffraction (XRD), and scanning electron microscopy (SEM) with elemental mapping (EDS). The antimicrobial activity of TiO 2 NPs with geraniol was assessed against Staphylococcus aureus , methicillin-resistant Staphylococcus aureus (MRSA), and Escherichia coli . The minimum inhibitory concentration (MIC) values of modified NPs ranged from 0.25 to 1.0 mg/ml against all bacterial strains, and the live dead assay and fractional inhibitory concentration (FIC) supported the antibacterial properties of TiO 2 NPs with GER. Moreover, TiO 2 NPs with GER also showed a significant decrease in the biofilm thickness of MRSA. Conclusions Our results suggest that TiO 2 NPs with GER offer a promising alternative to antibiotics, particularly for controlling antibiotic-resistant strains. The surface modification of TiO 2 NPs by geraniol resulted in enhanced antibacterial properties against multiple bacterial strains, including antibiotic-resistant MRSA. The potential applications of modified TiO 2 NPs in the biomedical and environmental fields warrant further investigation.

A zero-field Co( ii ) single-molecule magnet is reported based on a 2-formylphenoxyacetic acid derivative, and the study is complemented by theoretical calculations, resulting in the formulation of a correlation between the electronic structure and magnetic anisotropy.

Objectives Resistance to antibiotics among bacteria of clinical importance, including Staphylococcus aureus, is a serious problem worldwide and the search for alternatives is needed. Some metal complexes have antibacterial properties and when combined with antibiotics, they may increase bacterial sensitivity to antimicrobials. In this study, we synthesized the iron complex and tested it in combination with ampicillin (Fe16 + AMP) against S. aureus . Methods An iron complex (Fe16) was synthesized and characterized using spectroscopy methods. Confirmation of the synergistic effect between the iron complex (Fe16) and ampicillin (AMP) was performed using ζ – potential, infrared spectra and FICI index calculated from the minimum inhibitory concentration (MIC) from the checkerboard assay. Cytotoxic properties of combination Fe16 + AMP was evaluated on eukaryotic cell line. Impact of combination Fe16 + AMP on chosen genes of S. aureus were performed by Quantitative Real-Time PCR . Results The MIC of Fe16 + AMP was significantly lower than that of AMP and Fe16 alone. Furthermore, the infrared spectroscopy revealed the change in the ζ – potential of Fe16 + AMP. We demonstrated the ability of Fe16 + AMP to disrupt the bacterial membrane of S. aureus and that likely allowed for better absorption of AMP. In addition, the change in gene expression of bacterial efflux pumps at the sub-inhibitory concentration of AMP suggests an insufficient import of iron into the bacterial cell. At the same time, Fe16 + AMP did not have any cytotoxic effects on keratinocytes. Conclusions Combined Fe16 + AMP therapy demonstrated significant synergistic and antimicrobial effects against S. aureus . This study supports the potential of combination therapy and further research.

The new ferrocene-based metalloligand bis (N-4-[3,5-di-(2-pyridyl)-1,2,4-triazoyl])ferrocene carboxamide (L) was prepared through derivatization of 1,1′-ferrocenedicarboxylic acid with 4-amino-3,5-di(pyridyl)-4H-1,2,4-triazole. The composition and purity of L in the solid state was determined with elemental analysis, FT-IR spectroscopy, and its crystal structure with single-crystal X-ray analysis, which revealed that the substituted cyclopentadienyl rings adopt the antiperiplanar conformation and the crystal structure of L is stabilized by O–H···N and N–H···O hydrogen bonds. The molecular properties of L in solution were investigated with NMR and UV-VIS spectroscopies, and cyclic voltammetry disclosed irreversible redox behavior providing one oxidation peak at E1/2 = 1.133 V vs. SHE. Furthermore, the polymeric FeII complex {Fe(L)(C(CN)3)2}n (1) was prepared and characterized with elemental analysis, FT-IR spectroscopy, 57Fe Mössbauer spectroscopy, and magnetic measurements. The last two methods confirmed that a mixture of low- and high-spin species is present in 1; however, the spin crossover properties were absent. The presented study was also supported by theoretical calculations at the DFT/TD-DFT level of theory using TPSS and TPSSh functionals.

Two new iron(III) complexes, (TrBA)[Fe(azp)(2)] (1) and (TrPA)[Fe(azp)(2)] (2) (H(2)azp = 2,2' - dihydrox-yazobenzene, TrBA = tributylammonium and TrPA = tripropylammonium) were prepared by reaction of the azo dye H(2)azp, tributylamine (or tripropylamine) and FeCl3 in methanolic solution. The crystal structure of 1 was determined by single-crystal X-ray analysis. The asymmetric unit contains one tributylamonnium cation and one [Fe(azp)(2)](-) anion with an octahedrally coordinated Fe(III) ion with an FeN2O4 chromophore - the tridentate ligand azp(2-) is coordinated by two deprotonated phenolic oxygen atoms and one nitrogen atom from the azo group. The single-crystal X-ray analysis of 1 suggests that an N-H center dot center dot center dot O hydrogen bonding interaction between the TrBA cation and the [Fe(azp)(2)](-) anion may induce distortion of the coordination polyhedron resulting in a highspin complex. Magnetic investigation (DC magnetic data) revealed a high-spin state in the studied temperature range (2-300 K) for both 1 and 2. AC susceptibility measurements for 1 showed a field-induced slow relaxation of magnetization with an atypical temperature dependence of the relaxation time. Moreover, the cryogenic and room temperature Fe-57 Mossbauer spectroscopy parameters confirmed the high-spin state of 1. The study was also supported by theoretical calculations at the DFT level of theory.

Two cobalt(II) complexes with 2-[2-[2-(1H-benzimidazol-2-yl)ethylsulfanyl]ethyl]-1H-benzimidazole (tebb) of compositions [Co(tebb)Cl2]n center dot nCH3OH (1) and [Co(tebb)Br2]n center dot 3/2nCH3OH (2) have been prepared. Their poly-meric structures were determined by X-ray crystallography. In both cases, the central cobalt(II) atoms are in tetrahedral vicinity. There are two halogen anions and two nitrogen atoms of neighboring benzimidazole rings coordinated to cobalt. Methanol molecules are outside the coordination sphere and connected by hydrogen bonds to polymeric molecules. Magnetic properties of the complexes have been studied in the temperature range of 2-300 K. The moderate values of the zero-field splitting parameters were determined, D =-7.2(2) cm-1 for 1 and D =-3.7(1) cm-1 for 2. The theoretical calculations based on CASSCF/NEVPT2 method supported these findings.

The tetranuclear Cu(II) complex [Cu4(3-Mepy)8(H2L)2(ClO4)2]·(3-Mepy)2·(H2O)2 (1), where H5L = [(4-bromophenyl)(hydroxy)methylene]bis(phosphonic acid) and 3-Mepy = 3-methylpyridine, was prepared and characterized by elemental analysis, FT-IR spectroscopy, single-crystal X-ray analysis and magnetic measurements. The analysis of magnetic properties of 1 supported by DFT theoretical calculations revealed interplay between ferromagnetic exchange (J2 = J3 = 20.0 cm-1) and antiferromagnetic exchange (J1 = -64.4 cm-1) leading to S = 0 ground spin state.

In order to prepare an Fe(II) spin crossover (SCO) complex that could be consequently modified to a bimetallic coordination compound that possesses another magnetic property of interest, a specially designed ligand L-NH2 (1-(4-aminobenzyl)-4,11-bis(pyridine-2-ylmethyl)- 1,4,8,11-tetraazacyclotetradecane) was prepared. This ligand consists of a macrocyclic cyclam part containing two 2-pyridylmethyl pendant arms (expecting SCO upon Fe(II) complexation) and one p-aminobenzyl pendant arm with an NH2 group. The presence of this group enables the consequent transformation to various functional groups for the selective complexation of other transition metals or lanthanides (providing the second property of interest). Furthermore, the performed theoretical calculations (TPSSh/def2-TZVP) predicted SCO behavior for the Fe(II) complex of L-NH2. Thus, Fe(II) complexes [Fe(L-NH2)](ClO4)2 (1) and [Fe(L-NH2)]Cl2·6H2O (2) were synthesized and thoroughly characterized. Based on the crystal structure of an isostructural analogous Ni(II) complex [Ni(L-NH2)]Cl2·6H2O (3), the coordination number six was confirmed with an octahedral coordination sphere and a cis-arrangement of the pyridine pendant arms. The measured magnetic data confirmed the high-spin behavior of both compounds with large magnetic anisotropy (D = 17.8 for 1 and 20.9 cm−1 for 2 complemented in both cases also with large rhombicity), though unfortunately without any indication of the SCO behavior with decreasing temperature. The lack of SCO can be ascribed to the crystal packing and/or the non-covalent intermolecular interactions stabilizing the high-spin state in the solid state.

We report on the crystal structure and magnetic properties of four new ion-pair complexes.

A heptadentate macrocyclic ligand, H 2 L (3,12,18‐triaza‐6,9‐dioxabicyclo[12.3.1]octadeca‐1,14,16‐triene‐3,12‐diacetic acid) with two acetate pendant arms, and its complexes [Fe III L ]ClO 4 ( 1 ), [Fe II L ] · H 2 O ( 2 ), [Co II L ] · H 2 O ( 3 ), and [Ni II L ] · H 2 O ( 4 ) were synthesized. The complexes possess an axially compressed pentagonal bipyramidal geometry with the coordination numbers of 7 for 2 and 3 , and 6 + 1 for 4 . The magnetic susceptibility measurements revealed magnetic anisotropy for compounds 1 – 4 expressed by axial zero‐field splitting (ZFS) parameters ( D = –1.3 cm –1 for 1 , –9.6 cm –1 for 2 , 29.1 cm –1 for 3 , and –8.5 cm –1 for 4 ), with a rhombic ZFS ( E/D = 0, 0.006, 0, and 0.193, respectively). Field‐induced slow relaxation of magnetization was observed for the Co II complex 3 only. The structural and magnetic features of 1 – 4 were compared with those of similar complexes containing ligand with two 2‐pyridylmethyl pendant arms. Magnetic features of the complexes were also evaluated using theoretical calculations (DFT, CASSCF/NEVPT2).

Javorieite, KFeCl3, is a new mineral, commonly hosted by salt melt inclusions enclosed in vein quartz in the Biely Vrch porphyry gold deposit, in the Central Slovakia Volcanic Field in the Western Carpathians. The mineral name refers to the Javorie stratovolcano, which hosts most porphyry gold systems in this volcanic field. Within the inclusions, javorieite occurs in the form of small (up to 15 mu m) green anhedral crystals with high relief, which melt in the range 320-338 degrees C when heated. It is extremely hygroscopic and readily oxidised if exposed to the air. The daughter mineral was identified through comparison with the Raman spectra of the synthetic analogue, and through data obtained with the FIB-SEM-EBSD analytical technique. The combination of the three independent analytical tools on three different inclusions proved the match in chemistry and crystallography with synthetic KFeCl3. Javorieite is orthorhombic, the unit-cell parameters are a = 8.715(6) angstrom , b = 3.845(8) angstrom , c = 14.15(3) angstrom , V = 474.16(3) angstrom(3), Z= 4. Furthermore, the experimental data in the NaCl-KCl-FeCl2 system agree with the microthermometric behaviour of javorieite. The presence of javorieite in three other localities in this volcanic field was established by Raman spectroscopy. The distinctive Raman spectrum of javorieite (main bands at 66-69, 108-109, 119-120, 134-135, 235-237cm(-1)) can help in future studies of salt melt inclusions worldwide, including a quick recognition of shallow porphyry systems that can be potentially enriched in gold.

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 2-pyridylmethyl N-pendant-armed heptadentate macrocyclic ligand {3,12-bis(2-methylpyridine)-3,12,18-triaza-6,9-dioxabicyclo[12.3.1]octadeca-1,14,16-triene = L} and [M(L)](ClO4)2 complexes, where M = Mn(II) (1), Fe(II) (2), Co(II) (3), Ni(II) (4), and Cu(II) (5), were prepared and thoroughly characterized, including elucidation of X-ray structures of all the compounds studied. The complexes 1-5 crystallize in non-centrosymmetric Sohncke space groups as racemic compounds. The coordination numbers of 7, 6 + 1, and 5 were found in complexes 1-3, 4, and 5, respectively, with a distorted pentagonal bipyramidal (1-4) or square pyramidal (5) geometry. On the basis of the magnetic susceptibility experiments, a large axial zero-field splitting (ZFS) was found for 2, 3, and 4 (D(Fe) = -7.4(2) cm(-1), D(Co) = 34(1) cm(-1), and D(Ni) = -12.8(1) cm(-1), respectively) together with a rhombic ZFS (E/D = 0.136(3)) for 4. Despite the easy plane anisotropy (D > 0, E/D = 0) in 3, the slow relaxation of the magnetization below 8 K was observed and analyzed either with Orbach relaxation mechanism (the relaxation time τ0 = 9.90 × 10(-10) s and spin reversal barrier Ueff = 24.3 K (16.9 cm(-1))) or with Raman relaxation mechanism (C = 2.12 × 10(-5) and n = 2.84). Therefore, compound 3 enlarges the small family of field-induced single-molecule magnets with pentagonal-bipyramidal chromophore. The cyclic voltammetry in acetonitrile revealed reversible redox processes in 1-3 and 5, except for the Ni(II) complex 4, where a quasi-reversible process was dominantly observed. Presence of the two 2-pyridylmethyl pendant arms in L with a stronger σ-donor/π-acceptor ability had a great impact on the properties of all the complexes (1-5), concretely: (i) strong pyridine-metal bonds provided slight axial compression of the coordination sphere, (ii) substantial changes in magnetic anisotropy, and (iii) stabilization of lower oxidation states.

Three mononuclear lanthanide complexes of a 2-pyridylmethyl pendant-armed 15-membered ligand {(3,12-bis(2-pyridylmethyl)-3,12,18-triaza-6,9-dioxabicyclo-[12.3.1]octadeca-1,14,16-triene); L} with general formula [Ln(L)(H2O)(NO3)](NO3)2 (Ln = Tb (1), Dy (2), and Er (3)) are reported. Based on X-ray diffraction analysis of 1 and 2, the central lanthanide atoms are nine-coordinated with the N5O4 donor set originating from the ligand L and one coordinated water molecule and one monodentate-bonded nitrato ligand. The coordination geometry of the [LnN5O4] cores can be described as a muffin-like shape. Magnetic measurements revealed that all three compounds show field-induced single-molecule magnet behaviour, with estimated energy barriers U ≈ 44-82 K. The experimental study was complemented by CASSCF calculations showing a trend of an increasing first excited energy gap (Tb → Dy → Er) within the muffin-like geometry with the lowest magnetization tunnelling probability for the DyIII complex 2.