Search Results (453)

Flavanones retrieved in the leaves of Glycyrrhiza glabra (licorice), specifically glabranin (GLA), pinocembrin (PIN) and licoflavanone (LIC), represent a valuable source of bioactive natural products, although their isolation and handling are often complicated by their structural similarity and unfavorable physical properties. In this work, crystal engineering strategies were explored both to facilitate the selective separation of licorice flavanones and to improve their solid-state characteristics. Co-crystallization was investigated as a tool for the selective recognition of PIN from a GLA-rich chromatographic fraction. Guided by structural considerations and predictive analyses performed using the Co-Crystal Design and Hydrogen Bond Propensity (HBP) tools in CCDC Mercury (within CCDC-Materials), co-crystallization experiments were performed with pyridinic co-formers. 4,4′-Bipyridine (BPY) selectively formed a new co-crystal with PIN, enabling the capture of traces of this flavanone directly from the GLA-rich fraction. In contrast, nicotinic acid (NIC) did not form a co-crystal with PIN, consistently with the predicted preference for NIC self-association. In addition, a co-amorphous system between LIC and BPY was obtained by quench cooling, yielding a fully amorphous solid with improved handling properties compared to the waxy precursor. These results highlight the potential of crystal engineering approaches for the selective separation and solid-state modification of natural flavanones. Full article

The Activators Regenerated by Electron Transfer Atom Transfer Radical Polymerization (ARGET-ATRP) of vanillin methacrylate (VMA), a bio-based methacrylic monomer derived from vanillin, was systematically studied for the first time. The reaction conditions were optimized aiming at achieving good monomer conversions while preserving the antimicrobial aldehyde functionality. Bipyridine-based catalysts showed limited effectiveness, whereas polydentate aliphatic amines displayed higher activity. Kinetic studies showed linear profiles during the early stages of the polymerization before reaching a conversion plateau accountable to the depletion of the reducing agent, as confirmed by reactivation experiments. The resulting polymer (PVMA) exhibited a glass transition temperature comparable to that of poly(styrene), emerging as a potential bio-derived alternative to fossil-based thermoplastic materials. Furthermore, preliminary in vitro tests demonstrated that PVMA has potential antimicrobial activity against both Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive). 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

Indane-1,3-dione and 1,4-dihydropyridine (1,4-DHP) scaffolds are of significant interest in medicinal chemistry. Herein, we report the synthesis characterization of a new lipid-like indane-1,3-dione–1,4-DHP betaine, 2-(3′,5′-bis((dodecyloxy)carbonyl)-2′,6′-dimethyl-1′,4′-dihydro-[3,4′-bipyridin]-1-ium-1-yl)-1,3-dioxo-2,3-dihydro-1H-inden-2-ide (3). Compound 3 was synthesized from 2,2-dicyanomethylideneindan-1,3-dione (1) oxide and a didodecyl-substituted 1,4-DHP derivative 2 and characterized by UV–Vis spectroscopy, ¹H-NMR, ¹³C-NMR, and HRMS. The obtained results demonstrate a promising strategy for the design of delivery agents, exploiting the lipid-like properties of the synthesized betaine. 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

The development of stable and sensitive fluorescent sensors for metal ion detection remains a challenge in materials chemistry. Although hydrogen-bonded organic frameworks (HOFs) have shown great potential in luminescent applications, their practical use is often limited by structural instability. In this work, we present a novel charge-assisted HOF, termed FDU-HOF-21 ([H(NH₂Bpy)]₂(TPE)), constructed from a tetraphenylethylene (TPE)-based carboxylic acid ligand (H₄TCPE) and 2,2′-bipyridine-5,5′-diamine (NH₂Bpy). Single-crystal X-ray diffraction (SCXRD) reveals a stable three-dimensional framework stabilized by an extensive hydrogen-bonding network and reinforced by charge-assisted hydrogen bonds (CAHBs), and it exhibits exceptional stability across various solvents and pH conditions. Moreover, FDU-HOF-21 serves as a highly sensitive and selective fluorescent turn-on sensor for Al³⁺ ions, with a lowest limit of detection (LOD) of 1.7 × 10⁻⁶ M. Characterization and time-dependent density functional theory (TDDFT) calculations reveal that the fluorescence enhancement originates from the suppression of non-radiative decay likely due to the reduction in intermolecular charge transfer (Inter-CT) during the emission process, coupled with the restricted intramolecular rotation upon Al³⁺ chelation. Full article

Background/Objectives: This study focused on synthesizing novel alkenyl derivatives of azinylferrocenes and evaluating their potential as Alzheimer’s disease (AD) therapeutics. Methods: 1-Azinyl-1′-acetylferrocenes were obtained by regioselective acetylation of azinylferrocenes, followed by the Wittig reaction or reduction of 1-azinyl-1′-acetylferrocenes and subsequent dehydration of the resulting alcohols. The synthesized compounds underwent the following biological activity testing relevant to AD: inhibition of acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and off-target carboxylesterase (CES); antioxidant capacity (ABTS and FRAP assays); inhibition of Aβ₄₂ self-aggregation (thioflavin method); blocking AChE-induced β-amyloid aggregation (propidium displacement); and cytotoxicity in SH-SY5Y and MSC-Neu cells (MTT assay). Results: Quinoline and bipyridine derivatives demonstrated effective cholinesterase inhibition, especially quinoline 7b (AChE IC₅₀ 3.32 μM; BChE IC₅₀ 3.68 μM), while acridine derivatives were poor inhibitors. Quantum chemical (QC) calculations predicted that acridine derivatives were especially prone to form stable dimers. Molecular docking into protein targets generated by an AlphaFold3 reproduction code showed that these dimers were too bulky to access enzyme active sites, yet they could bind to protein surfaces to inhibit Aβ₄₂ self-aggregation and displace propidium from the AChE peripheral anionic site. All compounds showed high antioxidant activity in ABTS and FRAP assays, with quinoline derivatives being 2–4 times more potent than Trolox. QC calculations supported these findings. Quinoline and bipyridine derivatives also exhibited low cytotoxicity and scant CES inhibition. Conclusions: Overall, the synthesized ferrocenes, particularly the quinoline and bipyridine derivatives, appear promising for further research as multifunctional therapeutic agents targeting AD due to their anticholinesterase, antiaggregating, and antioxidant activities combined with low toxicity. 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

The reaction of 4,4′-bipyridine (C₁₀H₈N₂) with the alkali metal pentacyanocyclopentadienides [Na{C₅(CN)₅}(MeOH)] and [KC₅(CN)₅] gives the coordination polymers [Na{C₅(CN)₅}(EtOH)(H₂O)(C₁₀H₈N₂)] (1) and [K{C₅(CN)₅}(H₂O)₂] • 2 (C₁₀H₈N₂) (2) after recrystallization from EtOH. Both compounds show octahedral coordination around the metal ion with a NaN₄O₂ and KN₂O₄ environment. The [C₅(CN)₅] acts as a 1,1-bridging ligand in 1 and a 1,2-bridging ligand in 2. The 4,4′-bipyridine acts as a N,N′-bridging ligand between dimeric [Na₂(EtOH)₂(H₂O)₂(µ-{C₅(CN)₅}₂] units, while it acts only as a guest molecule in the voids between polymeric [K(µ-H₂O)_4/2{µ-C₅(CN)₅}_2/2]_∞ chains. Both compounds employ multiple hydrogen bonds and π stacking to stabilize the crystalline structures. Full article