Search Results (282)

This study reports the synthesis and characterization of a dinuclear zinc(II) complex, [Zn₂(L1)₂(L2)]·DMF·Et₃N (C₄₅H₅₄F₂N₁₀O₅S₂Zn₂), constructed from a fluoro-substituted thiosemicarbazone Schiff base ligand (2-(3-fluoro-5-hydroxybenzylidene)-N-methylhydrazine-1-carbothioamide, L1) and a rigid bipyridine auxiliary ligand (1,4-di(pyridin-4-yl)-2,5-dimethoxybenzene, L2) under solvothermal conditions. Single-crystal X-ray diffraction analysis reveals that the complex crystallizes in the monoclinic space group C2/c, featuring discrete dinuclear [Zn₂] units in which each Zn(II) center adopts a distorted square pyramidal geometry. These dinuclear units are extended into one-dimensional zigzag chains along the crystallographic c-axis via bridging L2 ligands, and further assembled into a two-dimensional supramolecular layer through hydrogen-bonding interactions involving lattice triethylamine and DMF molecules, ultimately forming a three-dimensional network. Both DMF and triethylamine molecules are disordered about a twofold rotation axis. This work highlights the structural directing roles of the fluoro-substituted multidentate Schiff base ligand and the rigid auxiliary ligand in the assembly of zinc(II) coordination polymers. Full article

Silver complexes are potential antimicrobial agents that trigger destructive processes in bacterial cells, leading to their death. Their ability to simultaneously stimulate tissue regenerative properties also makes them promising components in the development of medical materials. A common complication arising from the treatment of bone tissue damage is hospital-acquired infection, requiring repeated revision surgeries. The use of bone grafts with antibacterial properties can help solve this problem. New pyridine complexes of silver(I) with thiophenecarboxylic (Htph) and nitric acid anions have been synthesized: [Ag(tph)(py)₂]_n·nHtph (1, py—pyridine) and [Ag(bpy)]_n·nNO₃ (2, bpy—4,4′-bipyridine), the structures of which have been determined using X-ray analysis. Despite the fact that 2 is a known structure, we were able to obtain new cell parameters by conducting an X-ray diffraction analysis at a lower temperature of 100 K. According to X-ray diffraction data, both compounds are polymers in which the cationic part is formed by linear fragments (CN_Ag = 2) [Ag(py)₂]⁺ (1)/[Ag(bpy)₂]⁺ (2), and acid anions act as counterions. The presence of intermolecular and non-valent π-π interactions provides additional stabilization of supramolecular levels. Aqueous solutions 1 and 2 are stable for two weeks, according to UV-Vis data. Incubation of crosslinked resorbable polymer matrices functionalized separately with complex 1 or 2 in saline solution revealed a sustained, prolonged release of silver ions over 14 days. Evaluation of the antimicrobial potential of 1 and 2 against Gram-positive/Gram-negative species and fungi demonstrated moderate, controlled bacteriostatic growth inhibition broadly across tested strains, confirming the bifunctionality of the crosslinked hybrid matrix systems—moderate suppression of bacterial growth while simultaneously stimulating tissue regeneration. An increase in cell viability, expressed in their active proliferation under the influence of complexes 1 and 2 up to 156%, as well as calcium deposition, indicates the high cytocompatibility and pro-mineralization capacity of the new compounds. Full article

In this study, emodin was used as the starting material to synthesize two novel ligands, L1 and L2, containing bipyridine or phenanthroline moieties. Seven metal complexes (1–7) were obtained through coordination with Co, Rh, Ru, and Pt ions. Their structures were confirmed via NMR, HRMS, UV–Vis, IR, HPLC and SC-XRD analyses. The MTT assay showed that L1 and complex 2 selectively inhibited HepG-2 cells, with IC₅₀ values of 8.77 μM and 6.10 μM, respectively. Both compounds exhibited stronger activity than cisplatin (9.05 μM) and low toxicity toward normal 293T cells. Mechanistic studies demonstrated that they induced G2/M phase arrest by regulating Cyclin B1 and P21 expression, which was accompanied by ROS and Ca²⁺ accumulation, mitochondrial membrane potential disruption, and activation of the Caspase-9/3 cascade. Complex 2 showed superior antitumor activity to L1, and this finding was further supported by molecular docking analysis. In sum, Rh(III) complex 2 was identified as a selective and mechanistically defined anti-hepatocellular carcinoma lead compound, providing a potential strategy for the development of natural product-based metal anticancer agents. Full article

Cationic lanthanide luminophores remain underexplored compared with their neutral analogues, despite attractive features for solution-processed electroluminescent devices. Here we report the synthesis and characterization of five europium(III) cationic complexes of the type [Eu(L^{N,N})₂(L^{O,O})₂][PF₆], where L^{N,N} = 2,2′-bipyridine, 1,10-phenanthroline, or bathophenanthroline and L^{O,O} = acetylacetonate (acac) or hexafluoroacetylacetonate (hfac). These complexes are obtained in good yield via one-pot reactions from EuCl₃·6H₂O, β-diketonates, and diimine ligands, and are confirmed by FT-IR and RAMAN spectroscopies, elemental analysis, and single-crystal X-ray diffraction to possess well-defined EuO₄N₄ coordination spheres with PF₆ counterions. UV–Vis spectra show intense ligand-centered π–π* bands below ~300 nm and weak visible tails, consistent with efficient antenna sensitization and negligible direct Eu(III) f–f absorption. All complexes exhibit characteristic Eu(III) emission between ~575 and 725 nm, dominated by the ⁵D₀ → ⁷F₂ transition near 610–620 nm for all complexes and ⁵D₀ → ⁷F_3,4 transitions for 4 and 5, with similar line patterns but markedly different intensities. Replacing acac with hfac dramatically enhances performance with the quantum yields increasing from 15–18% to 85–93%, and excited-state lifetimes from 1.01–1.53 ms to 2.50–3.25 ms. These gains are attributed to improved ligand triplet to Eu(III) ⁵D₀ energy matching and reduced multiphonon relaxation, establishing these cationic Eu(III) complexes as promising emitters for solution-processable photonic devices. Full article

The clinical advancement of the ruthenium complex [bis(4,4′-dimethyl-2,2′-bipyridin){2-(2,2′:5′,2″-terthiophen-5-yl)imidazo[4,5-f][1,10]phenanthroline}ruthenium]dichloride (TLD-1433) has provided a breath of fresh air to the bioinorganic chemistry of metal-based complexes, especially those developed around Ru(II). The success of TLD-1433 resides in its dual metal–ligand photodynamic therapy mechanism, which allows for the treatment of hypoxic cancer. The presence of α-terthiophene at the periphery of the polypyridyl complex positively modified the photophysical property of the ruthenium complex; however, it is unclear if it possesses other favorable attributes. Considering the tremendous structural and photophysical diversity of terthiophene derivatives (14 isomers), as well as α-terthiophene’s recognized nematocidal activity, the following questions can be asked: What is the main role of α-terthiophene in TLD-1433? Is it to act as a pharmacophoric element, a photo-physical modulator, or a simple structural motif? Can a terthiophene motif be beneficial for other metal-based or organic drugs? Full article

A set of new coordination compounds of the formula [RuNO(L)Cl₃], with L representing the bidentate ligands bipyrimidine (bpym), bipyridine (bpy), or phenanthroline (phen), was prepared and fully characterized. For the isomeric species fac-[RuNO(bpym)Cl₃] (1), fac-[RuNO(phen)Cl₃] (2), mer-[RuNO(phen)Cl₃] (3), fac-[RuNO(bpy)Cl₃] (4), and mer-[RuNO(bpy)Cl₃] (5), an evaluation of the photoresponse in DMSO was performed under excitation with 450 nm using a continuous-flow arrangement that enabled the simultaneous acquisition of IR and UV-Vis spectral data. Quantum yields for photoinduced release of NO were determined as follows: 5.4 ± 0.5% for fac-[RuNO(bpym)Cl₃] (1); 0.8 ± 0.1% for fac-[RuNO(phen)Cl₃] (2); 0.6 ± 0.1% for mer-[RuNO(phen)Cl₃] (3); 3.7 ± 0.1% for fac-[RuNO(bpy)Cl₃] (4); 2.1 ± 0.1% for mer-[RuNO(bpy)Cl₃] (5). The product of the photolysis of compound 5 in acetonitrile solution was isolated and structurally characterized as mer-[Ru(CH₃CN)(bpy)Cl₃] (6). Taking into account the presence of typical DNA intercalating ligands, the complexes can be potentially exploited as photoNORMs. Full article

Well-defined, small-molecule, platinum-centered coordination compounds are of continued interest in both basic and applied research, particularly in medicinal chemistry and pharmaceuticals (i.e., cisplatin). Organoplatinum(IV) complexes have been reported to exhibit substantial in vitro cytotoxicity across a range of cancer cell lines. Compared with coordinatively unsaturated platinum(II) species, electronically and coordinatively saturated platinum(IV) complexes are generally more inert, reducing undesirable side reactions in plasma and cellular environments and potentially improving their safety profiles as chemotherapeutic agents. In addition, the presence of organic ligands can enhance lipophilicity, facilitating passive diffusion across cell membranes. Here, we report the synthesis, structural characterization, and in vitro anticancer activity of a series of organoplatinum(IV) complexes of the general formula Pt(CH₃)₂I₂{n,n′-dimethyl-2,2′-bipyridine} (n,n′ = 4,4′; 5,5′; 6,6′). The 5,5′- and 6,6′-dimethyl isomers were characterized by single-crystal X-ray diffraction. All three dimethyl-substituted complexes, along with the parent compound, Pt(CH₃)₂I₂{2,2′-bipyridine}, were evaluated for cytotoxic activity against a panel of 60 human cancer cell lines. Whereas Pt(CH₃)₂I₂{2,2′-bipyridine} and the 4,4′- and 5,5′-dimethyl derivatives displayed limited cytotoxicity, the 6,6′-dimethyl isomer exhibited notable activity, particularly against the colon cancer cell line HCT-116 (LC₅₀ = 8.17 μM) and the ovarian cancer cell line OVCAR-3 (LC₅₀ = 7.34 μM). The enhanced cytotoxicity of the 6,6′-dimethyl derivative is attributed, at least in part, to the relatively facile dissociation of the 6,6′-dimethyl-2,2′-bipyridine ligand from the platinum(IV) center, suggesting that sterically induced ligand lability plays an important role in modulating biological activity in this particular compound, giving new structural activity impetus for potential drug molecules. Full article

This study investigates the rational design of a dinuclear zinc(II) coordination polymer, (C₃₆H₃₄Br₂N₈O₄S₂Zn₂), to explore how halogen substitution and ligand choice modulate structural architecture, contributing to the development of functional coordination polymers with tailored properties. The complex was synthesized from a bromo-substituted semicarbazone Schiff base ligand (L1) and a rigid bipyridine linker (L2) under solvothermal conditions, and its structure was elucidated using single-crystal X-ray diffraction (SCXRD), complemented by characterization via powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and infrared (IR) spectroscopy. Crystallographic analysis reveals that the complex crystallizes in the triclinic space group P-1, forming discrete dinuclear units where each Zn(II) center adopts a distorted square–pyramidal geometry; these units are extended into one-dimensional chains by bridging L2 ligands and further assembled into a three-dimensional supramolecular network through hydrogen-bonding interactions. PXRD confirms the high phase purity of the bulk material, TGA indicates notable thermal stability up to 130 °C, and IR spectroscopy validates the coordination modes and hydrogen-bonding network. This work elucidates the critical role of the bromo substituent and rigid ancillary ligands in modulating the solid-state structure of the zinc(II) complex. The revealed structure-directing principles provide a valuable reference for the rational design of functional coordination polymers. Full article

Recent findings demonstrate that concentrated sulfuric acid supports rich organic chemistry, including the stability of the canonical DNA bases adenine, thymine, guanine and cytosine. Yet, due to full protonation in concentrated sulfuric acid, these bases may not pair as effectively as they do in water. We are therefore motivated to study nucleic acid bases that pair via hydrophobic and van der Waals interactions instead of canonical hydrogen bonding. Here, we investigate the stability of 14 selected, commercially available alternative nucleobases in concentrated sulfuric acid to evaluate their potential for forming DNA-like polymers in this solvent. The reactivity of compounds 1–14 have not been previously investigated in concentrated sulfuric acid. We incubate the selected compounds in 98% and 81% w/w sulfuric acid and monitor their stability using ¹H and ¹³C NMR spectroscopy over 3 weeks at room temperature. In 98% w/w sulfuric acid, six bases—benzo[c][1,2,5]thiadiazole (1), 2,2′-bipyridine (2), 1,1′-biphenyl (3), 1-methoxy-3-methylbenzene (MMO2) (7) and 1-chloro-3-methoxybenzene (ClMO) (13), and 2,4-difluorotoluene (14)—remain soluble and stable with no detectable degradation. A few compounds show non-destructive reactivity, like sulfonation (compound 3) or H/D exchange (compounds 7, 13, 14). The other compounds react rapidly or are insoluble in 98% w/w sulfuric acid. In 81% w/w sulfuric acid, only compounds 1 and 2 remain stable and soluble, while other selected compounds are insoluble or unstable. Our findings identify a subset of alternative bases stable in concentrated sulfuric acid, advancing efforts towards the design of an example genetic-like polymer in this unusual solvent. Our work further highlights sulfuric acid’s potential for supporting complex organic chemistry, with implications for astrobiology, planetary science of Venus and synthetic biology. Full article

Three complexes of Zn(II) with the general formulas {[Zn(H₂O)₄(4,4′-BiPy)](NO₃)₂·2NA·H₂O}_n(1), [Zn(NA)₂Br₂]·2NA (2), and [Zn₂(CH₃COO)₄(NA)₂]·2H₂O (3), where 4,4′-BiPy = 4,4′-bipyridine and NA = nicotinamide, have been synthesized and characterized by means of single-crystal X-ray diffraction (complexes 1 and 2), elemental analysis, FT-IR, fluorescence, ¹H and ¹³C NMR spectroscopy (complexes (2) and (3)), and thermogravimetric analysis. A previously reported complex, [Zn(NA)₂(H₂O)₄](NO₃)₂·2H₂O, was used as a precursor for the synthesis of coordination compounds (1) and (2). X-ray data show that (1) is a 1D polynuclear compound, whereas complex (2) is mononuclear. The Zn(II) ions adopt a slightly distorted octahedral geometry in the polymer and a slightly distorted tetrahedral geometry in the monomer. The antimicrobial activity of complexes (2) and (3) was also evaluated, and complex (3) exhibited superior antimicrobial properties, particularly against the C. albicans strain. Full article

Two crystalline complexes, (2,2′-bipyridine)Cu(CH₃COO)₂·5H₂O (3) and (2,2′-bipyridine)Cu(CH₃COO)₂·CH₃CN (4), have been isolated and characterized by low-temperature single-crystal X-ray diffraction experiments. Crystals of phase 3 were studied previously at room temperature (296 K) under conditions leading to rapid desolvation and less distinct characterization of the waters of crystallization. With our redetermination of 3 at 100(2) K, we present a detailed description of ribbon-like structure formed by water molecules in crystals of (2,2′-bipyridine)Cu(CH₃COO)₂·5H₂O. Acetate oxygens are linked by hydrogen-bonding to two inequivalent waters separated by 4.72 Å; the other three water molecules are trapped in polymeric ribbons of anticooperative hydrogen-bonded six-membered rings fused with cooperative hydrogen-bonded four-rings. Water oxygens of the fused ring ribbons associate only with other water oxygens, and this water structure has a local density and pair distribution function which resembles that of liquid water. Crystals of 4 are monoclinic, with acetonitrile of solvation unassociated with the complex. In both 3 and 4, bipyridine planes interleave through π-aryl stacking. Full article

Although various phosphorescent organic light-emitting diodes (PhOLEDs) have been developed, their lifetimes remain shorter than those of fluorescent OLEDs. In this study, a novel Pt(II) complex featuring a tetradentate ligand composed of bipyridine and phenoxypyridine, referred to as LL-O, was synthesized and fully characterized to evaluate its potential as a dopant for PhOLEDs. Geometry-optimized calculations indicate that LL-O adopts a distorted square–planar structure around the Pt(II) center. The complex displays bluish-green emission with maxima at 490 and 518 nm. However, it exhibits a low photoluminescence quantum yield (4%), primarily due to a dominant non-radiative decay rate that surpasses the radiative decay rate. Natural transition orbital analysis reveals that the emission of LL-O originates from a combination of triplet ligand-centered (³LC), triplet ligand-to-ligand charge-transfer (³LL′CT), and triplet metal-to-ligand charge-transfer (³MLCT) transitions. This compound also demonstrates high thermal stability (decomposition temperature > 340 °C) and an appropriate HOMO energy level (−5.58 eV), making it suitable for use as a dopant in versatile PhOLEDs. Full article

Three new Cu(II) coordination polymers with 4,4′-bipyridine (bpy) were synthesized by hydrothermal reactions and their structures determined by single crystal X-ray diffraction. [Cu(bpy)₃(H₂O)₂](bpy)(PF₆)₂(H₂O)₃ (1) is built from bpy-bridged chains, [Cu(bpy)₂(H₂O)₂](bpy)(PF₆)₂(H₂O)₆ (2) from layers, and in [Cu(bpy)₂(NO₃)](bpy)(PF₆)₂(H₃O)(H₂O) (3) the layers are further connected by nitrate to a cuboid lattice. The magnetic properties of 3 are compared to [Cu(bpy)₂(H₂O)₂](SiF₆) (4) and [Cu(pyz)(bpy)(H₂O)₂](PF₆)₂ (5), where pyz = pyrazine. 3–5 are weakly coupled two-dimensional S = 1/2 antiferromagnetic Heisenberg lattices with 0.86 K < J < 1.47 K. Full article

Anthraquinones are molecules with numerous biological properties that can act as DNA intercalators and topoisomerase IIa inhibitors. In this work, the development of technetium-99m radiotracers was pursued via the technetium-tricarbonyl “2 + 1” mixed-ligand approach, fac-[^99mTc][Tc^I(CO)₃(NN′)(N)]⁺, with a (N,N′) bidentate chelator and a N co-ligand. In one approach, the ligands used were 2,2′-bipyridine (bpy) and N-functionalized-imidazole, where imidazole was conjugated to an anthraquinone moiety. In the other approach, 2-picolylamine and imidazole were used as the mixed-ligand system, where picolylamine was conjugated to an anthraquinone moiety. The synthesis of the ligands was achieved by reaction of 2-picolylamine with a suitably functionalized anthraquinone (Aqpa) or anthrapyrazole (Appa) and imidazole with a suitably functionalized anthraquinone (Aqim). The rhenium reference compounds, fac-[Re^I(CO)₃(bpy)(Aqim)]⁺ with bpy as a bidentate chelator and fac-[Re^I(CO)₃(Aqpa or Appa)(Im)]⁺, with imidazole (Im) as a co-ligand, were synthesized and characterized with spectroscopic methods. The radiotracer technetium-99m complexes fac-[^99mTc][Tc(CO)₃(bpy)(Aqim)]⁺ and fac-[^99mTc][Tc(CO)₃(Aqpa or Appa)(Im)]⁺ were prepared and characterized with standard methods. The purified radiotracers displayed high stability (≥90%) after incubation 24 h in 1 mM L-histidine or rat plasma. The tracers’ cell uptake was evaluated in vitro in CT-26 cells, and their pharmacokinetic properties and tumor uptake were evaluated in vivo in CT26-tumor-bearing mice. The “2 + 1” technetium-tricarbonyl approach leads to in vitro stable tracers, and this mixed-ligand system shows promise for further evaluation. Full article

This work investigates the coordination compound [Zn(2,2-bpy)₃](BF₄)₂ as a catalyst for the molecular reduction of CO₂. The synthesis and characterization of the complex are reported, along with electrochemical studies conducted both in the presence and absence of CO₂. In the absence of CO₂, reduction of the 2,2′-bipyridine ligands was observed (Epa(I) = −1.84 V vs. Fc/Fc⁺ and Epa(II) = −2.18 V vs. Fc/Fc⁺). In contrast, under a CO₂ atmosphere, catalytic molecular activity toward CO₂ reduction was detected (Epk(I) = −1.90 V vs. Fc/Fc⁺ and Epk(II) = −2.18 V vs. Fc/Fc⁺). Foot of the wave analysis (FOWA) was employed to determine the catalytic rate constant (k = 1.352 × 10³ M⁻¹ s⁻¹) for CO₂ reduction. Spectroelectrochemical experiments were also carried out in both the presence and absence of CO₂. Density functional theory (DFT) calculations were conducted to understand the interaction of the complex with CO₂. Bulk electrolysis and FTIR analysis suggest that oxalate is the product of the CO₂ reduction. Full article