The reprocessing of spent nuclear fuel (SNF) and high-level waste (HLW) requires the development of selective methods for the extraction, separation, and monitoring of actinides, lanthanides, and toxic impurities. In this work, a series of alkyl-aryl diamides of 1,10-phenanthroline-2,9-dicarboxylic acid (DAPhen) were investigated as ionophores for potentiometric sensors and as ligands for various divalent metal ions and f-elements. It was shown that the developed sensors exhibit pronounced potentiometric responses toward di- and trivalent cations. The sensitivity toward divalent metal ions increases when moving from alkaline-earth to transition and heavy metals and correlates well with the results of solvent extraction experiments. The sensors display reproducible responses toward trivalent lanthanide ions, with sensitivities decreasing along the lanthanide series, and some of the sensors also respond efficiently to Th4+ and UO22+. For the first time, solid complexes of DAPhen ligands with Co(NO3)2, Pb(NO3)2, and PdCl2 were obtained and investigated by single-crystal X-ray diffraction. The Co2+ complex exhibits an unusual seven-coordinate environment involving tetradentate ligand coordination and three water molecules in the inner coordination sphere. In the case of Pb2+, pronounced differences in the structures of complexes with chlorinated and nonchlorinated diamides were revealed, including the formation of dinuclear and mononuclear species with different coordination numbers. For Pd2+, square-planar complexes are formed, accompanied by a noticeable distortion of the phenanthroline core. Overall, the obtained results demonstrate the potential of DAPhen diamides for the development of potentiometric sensors and solvent extraction systems for the monitoring and reprocessing of spent nuclear fuel.

The molecule Ptrop3 contains in each trop unit (trop = dibenzo[a,d]cyclohepten-5-yl) a rigid central seven-membered ring with an olefinic binding site making Ptrop3 potentially a tetradentate ligand. Nevertheless, in mononuclear CuI complexes, [Cu(Ptrop3)X] [X = Cl (2), OTf (3), BF4 (4')], this phosphane behaves mainly as a highly bulky ligand (cone angle approx. 250 °) and the interactions between CuI center and the C═Ctrop units are remarkably weak, such as in other related Cu trop-type complexes. The reaction of [Cu(Ptrop3)(OTf)] with Cu+ sources allows the preparation of dinuclear complexes [Cu2(μ2-Ptrop3)(μ2-X)]+ (X = Cl, OTf, TFA), which contain a μ2-bridging P center and in which the interaction between the CuI 2 core and the olefins is significantly enhanced. Experimental investigations and DFT calculations indicate that the uptake of a Cu+ ion by the mononuclear complex [Cu(Ptrop3)(OTf)] (3) is a kinetically and thermodynamically favorable process.

The development of efficient and practical catalytic asymmetric cis-dihydroxylation reactions using earth-abundant metal catalysts remains a major challenge; the cis-dihydroxylation of 1,4-quinones represents a vital gateway to enantioenriched cis-1,2-diols, which are privileged scaffolds for bioactive natural products and pharmaceuticals. Inspired by the asymmetric cis-dihydroxylation of aromatic and olefinic C═C bonds catalyzed by Rieske dioxygenases, we present a biomimetic strategy for the asymmetric cis-dihydroxylation of 1,4-quinones. Herein, we report an inexpensive and readily accessible nonheme manganese complex, supported by a tetradentate aminopyridine ligand featuring a rigid chiral diamine backbone and a sterically bulky triisopropylsilyl group, for the cis-dihydroxylation of 1,4-quinones by hydrogen peroxide and alkyl hydroperoxides; it is noted that this study reports the first example of using alkyl hydroperoxides as a terminal oxidant in cis-dihydroxylation reactions. Various 1,4-quinones were efficiently oxidized to cis-1,2-diols in synthetically useful yields with excellent chemo-, regio-, and enantioselectivity (up to 99% ee), along with complete diastereoselectivity. Mechanistic evidence from experimental and computational studies supports a highly electrophilic manganese(V)-oxo-hydroxo species as the active cis-dihydroxylating intermediate, although the formation mechanism of the high-valent manganese-oxo intermediate is different depending on the hydroperoxide oxidants. Moreover, a two-step mechanism is proposed for the manganese(V)-oxo-hydroxo-mediated asymmetric cis-dihydroxylation, such as the Re-face selective oxo attack on the less hindered C═C bond, followed by OH-rebound, with stereochemistry dictated by the initial oxo attack. Thus, this study delineates the first biomimetic oxidation strategy enabling asymmetric cis-dihydroxylation of 1,4-quinones mediated by a high-valent manganese-oxo species generated in the reactions of hydrogen peroxide and alkyl hydroperoxides.

Cisplatin’s chemotherapy is hindered by drug resistance and toxicity, making copper complexes a potential alternative. A novel copper(II) complex, [CuLBr], was synthesized from a tetradentate vicinal dioxime ligand (H2L) and characterized. [CuLBr] features a distorted square pyramidal geometry with a CuN4Br chromophore. DFT calculations showed a narrowed HOMO-LUMO gap and increased electrophilicity, enhancing its chemical reactivity. [CuLBr] exhibited potent biomimetic catalytic activity, functioning as an efficient superoxide dismutase mimic and catalase mimic. Biophysical studies (UV-Vis, fluorescence, and viscosity) demonstrated a strong, spontaneous affinity of [CuLBr] for calf thymus DNA and Human Serum Albumin, suggesting groove-binding and static quenching mechanisms. In vitro assays revealed superior anticancer activity against HepG-2, HCT-116, and MDA-MB-231 cell lines, with greater selectivity than the free ligand and doxorubicin. Molecular docking studies reveal a high binding affinity of [CuLBr] with key proteins, including ferredoxin-1 and VEGF. This may suggest potential dual mechanisms of action, involving the induction of cuproptosis and the inhibition of tumor angiogenesis. These findings position [CuLBr] as an effective multi-metal-based anticancer agent with advantageous selectivity.

Herein, we reporta series of Cr­(II) complexes containing triaryl,tetradentate ligands derived from o-phenylenediamidethat illuminate how rigid, chelating amido ligands facilitate Cr–Crbonding. The aminolysis reaction of Cr­[N­(SiMe3)2]2(thf)2 with H2(L1)a protonated N4 proligand containing flankingNMe2 groupsyielded square planar and mononuclearCr­(L1) (1), whereas the same reaction withN2S2 and N2O2 proligandswith flanking SMe and OMe groups yielded dinuclear [Cr­(L2)]2 (2) and [Cr­(L3)]2 (3). The structures of 2 and 3 revealed Cr–Cr distances of 2.3356(6) and 2.3481(5) Å,consistent with metal–metal bonding, which was confirmed bythe complete active space methods. The theoretical results suggestthat Cr–Cr bonding is assisted by the chelating nature of thebridging amido ligands, which fold the dinuclear structure and orientthe metals so that side-on overlap of Cr 3d orbitals can occur. Variable-temperatureSQUID magnetometry and spectroscopic data (e.g., UV–vis-NIR,Raman, and IR) reported for 1–3 show differencesindicative of the change in nuclearity and electronic structure. Collectively,these results reveal bridging amido ligand characteristics that supportmetal–metal bonding with Cr­(II), and they help account forthe wide range of metal–metal distances observed in dinuclear(or binuclear) Cr­(II) complexes containing Cr2N2 cores.

In this work, the Schiff base ligand N,N′- bis(salicylidene)-1,2-phenylenediamine (H2L) was synthesized through the condensation reaction of 2- hydroxybenzaldehyde with 1,2-phenylenediamine, yielding a tetradentate N2O2-type ligand. Complexes of this ligand with Mg2+ and Ca2+ ions were subsequently prepared in a 1:1 molar ratio, resulting in [MgCl2L] and [CaCl2L]. The ligand and its complexes were characterized by nuclear magnetic resonance (NMR), Fourier-transform infrared (FT-IR) spectroscopy and ultraviolet–visible (UV-Vis) spectroscopy. The spectral data confirmed the coordination of the ligand through its azomethine nitrogen and phenolic oxygen atoms. All complexes were found to be nonelectrolytic. Antibacterial activity of the ligand and its complexes was evaluated against Escherichia coli and Staphylococcus aureus and the results were compared with Gentamycin. Notably, the Mg(II) and Ca(II) complexes exhibited significantly enhanced activity against E. coli compared to the free ligand

A flexible tetradentate ligand, L,1,2,4,5-tetrakis((pyridin-4-ylthio)methyl)benzene, was designed to precisely construct topologically distinct handcuff-shaped molecules 1,2 and Double-Z cage 1 through coordination-driven self-assembly with building blocks (B1-B3). In particular, the size of the conjugated surfaces of B1-B3 and hydrogen bond-accepting properties of anions play critical roles in influencing the resulting topology, as supported by single-crystal X-ray diffraction (SCXRD), electrostatic potential (ESP), and independent gradient model (IGM) calculations. BF4- anions favored the formation of handcuff-shaped structures with smaller conjugated building blocks B1 and B2, while Double-Z Cage 1 with a larger conjugated building block B3. Intriguingly, when BF4- is replaced with OTf-, the stronger electron-donating and hydrogen bond-accepting capabilities of OTf- induce a topological transformation from Handcuff 2 to Double-Z Cage 3. Specifically, Handcuff 1 and Double-Z Cage 1 correspond to Handcuff 3 and Double-Z Cage 2, respectively, demonstrating how anion identity influences the final topology for similar building blocks. Furthermore, a remarkable in situ topological transformation from Handcuff 2 to Double-Z Cage 3 was achieved under mild conditions with the addition of KOTf to Handcuff 2, as confirmed by real-time 1H NMR monitoring. This work offers promising avenues for designing responsive molecular materials with tailored topologies.

The growing need for high-purity lanthanides demands more selective separation strategies. Existing approaches mainly follow lock-and-key or induced-fit principles: the former uses fixed binding cavities for size-based recognition and the latter relies on adaptive, energy-favored architectures. Although impressive trends such as reversed, V-shaped, and S-shaped selectivity have been achieved, cation-specific selectivity remains rare. Here, we show that an asymmetric ligand design at the atomic level can be highly effective. Introducing sulfur into a phenanthroline-diimine scaffold produced an asymmetrical ligand with unexpected Nd selectivity among light lanthanides. Spectroscopic titrations confirmed this behavior: despite lowering overall binding affinity, sulfur incorporation enhanced Nd selectivity by two orders over La and Eu. This validates the asymmetric ligand design as a promising route to f-element discrimination.

Abstract The present study describes the synthesis of mononuclear Co(II) ( 1 ), Ni(II) ( 2 ) and binuclear Cu(II) ( 3 ) chelates of the ligand ( L ): N,N′-(propane-1,3-diyl)bis(2-aminobenzamide). Their structural characterization was affirmed by different analytical, spectroscopic, thermal techniques, powder X-ray diffraction and DFT. Octahedral structure was assured for Co(II) ( 1 ), Ni(II) ( 2 ) and distorted square planar for Cu(II) ( 3 ) chelates. Also, the current work was to establish the impact of a high dose of γ -ray irradiation on their physical and chemical properties. In addition, the dc solid-state electrical conductivity of un-irradiated and γ -irradiated chelates have been performed. Changes in crystallite size and solid electrical conductivity were observed as a result of defect formation upon irradiation. The in vitro antimicrobial property of the chelates towards Staphylococcus aureus as Gram +ve bacteria, Escherichia coli as Gram −ve bacteria, and Candida albicans and Aspergillus niger as fungal strains was evaluated for unirradiated complexes. The outcomes of antimicrobial studies showed that the ligand and its complexes possess excellent to good activity towards the examined microorganisms.

This work reports the synthesis of four tetradentate Schiff base ligands— H 2 L X ; where X = Cl ( N,N ′-bis(5-chloro-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine), Br ( N,N ′-bis(5-bromo-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine), Me ( N,N ′-bis(5-methyl-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine), and OMe ( N,N ′-bis(5-methoxy-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine)—prepared by the reaction of 5-substituted salicylaldehydes and 2,2-dimethyl-1,3-propanediamine, and their subsequent Ni(II) and Cu(II) complexes. The structural characterization of all new compounds was confirmed by elemental (CHN) analysis, FT-IR, and 1 H NMR spectroscopy. Geometry optimization was performed using the B3LYP functional; the LanL2DZ basis set was applied for Cu and Ni, and 6-31G(d) for all other elements. This work focuses on the key interactions of the ligands and their Ni/Cu complexes with DNA and BSA. The results indicate that H 2 L Me and its Ni complex predominantly bind within the DNA minor groove, whereas the Cu complex favors major-groove interaction. H 2 L Me forms three key hydrogen bonds with the nucleotide bases (≈2.92–3.12 Å), while also interacting through a hydrogen bond (≈3.34 Å) with amino-acid residues within the active sites of BSA. These results offer a practical model for advancing Schiff-base ligand chemistry toward metallodrug development by enabling controlled biomolecular interactions that may improve efficacy and safety. • Four Schiff bases and their Ni and Cu complexes were synthesized and characterized. • The shift in C N and C O stretches corresponds to the change in bond lengths due to complexation. • Molecular docking demonstrated strong binding to DNA and BSA. • Free ligands form specific H-bonds and hydrophobic interactions with BSA.

Examining Pseudohalide (N3, NCS, NCO) Coordination in Nonheme Fe(II) and Fe(III) Complexes.

Integrated experimental and theoretical investigation of VO(II), Ni(II), and Ru(III) nanocomplexes derived from a tetradentate anthraquinone ligand: Sonochemical synthesis and therapeutic assessment

Design and synthesis of tunable schiff base complexes from bis-(2-oxoindolin-3-ylidene)anthracene-9,10-dione: Integrated structural, biological, and molecular modeling insights.

Abstract In this study, the ONNO type Schiff base ligand N, N’-bis(2-hydroxyphenylidene)-1,3-propanediamine (LH 2 ) was reduced and converted into a tetradentate phenolic amine ligand, N, N′-bis(2-hydroxybenzyl)-1,3-diaminopropane (L H H 2 ). First, a mononuclear [NiL H Cl(DMF)] 2 (DMF) complex (I) was obtained with the reduced ligand in dimethylformamide (DMF). CoCl 2 was then added to the complex I to give the heterodinuclear [NiL H CoCl 2 (DMF) 2 ] complex (II) . The complexes were characterized by elemental analysis, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and single-crystal X-ray diffraction (XRD). The XRD analysis of complex I revealed that one phenolic oxygen persisted in its coordinated phenol form, while the charge of Ni(II) was observed to be neutralized by a chloride ion and a phenolate ion. The Ni(II) center ion in the complex exhibited octahedral coordination, being surrounded by two phenolic oxygens, two aminic nitrogens, an oxygen from a DMF molecule, and a chloride ion. In complex II , the Ni(II) ion was coordinated by two phenolic oxygens, two aminic nitrogen, and two DMF oxygens. The Co(II) ion was found to have a tetrahedral coordination sphere with two phenolate oxygens and two chloride ions. Thermogravimetric analysis demonstrated distinct thermal behaviors for mononuclear and heterodinuclear complexes. The mononuclear complex exhibited stability up to 210 °C and an exothermic reaction at 510 °C in an oxygen atmosphere, resembling energetic materials. The heterodinuclear complex showed higher thermal stability and a distinct decomposition pathway, influenced by Co(II) coordination. These findings highlight the significance of heterometallic coordination in thermal properties and controlled decomposition applications.

Iron complexes of tetradentate macrocyclic ligands containing N-heterocyclic carbene (NHC) donors have been referred to as organometallic heme analogues, but they usually lack the redox noninnocence under oxidizing conditions that is characteristic of porphyrins. Here we report a novel NHC/N-donor hybrid macrocyclic ligand containing two trans NHC moieties, a pyridine and a redox active carbazolide fragment. Its FeII, FeIII and formal FeIV complexes have been isolated and comprehensively characterized, where UV/vis and 57Fe Mössbauer spectroscopies, SQUID magnetometry and density functional theory (DFT) calculations reveal that the latter are best described as FeIII systems antiferromagnetically coupled to a carbazolide-based organic π-radical. Two different redox series are obtained depending on the axial ligands: nitriles such as MeCN give low-spin (LS) configurations of the metal ion, while in case of weakly coordinating solvents and triflate anions the iron adopts an intermediate-spin (IS) configuration; MeCN binding constants have been determined. As in other heme analogues with NHC-based macrocycles, the strong equatorial σ-donor character raises the energy of the Fe(dx2-y2) orbital, making high-spin (HS) iron species inaccessible. The combined features of equatorial ligand redox noninnocence, restriction to LS/IS surfaces and tunability via the axial coligands makes this a promising platform for bioinspired reactivity such as the generation of reactive Fe/Ox intermediates.

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.

New antimony(V) complexes, 1 and 2, containing the redox-active ligands N,N'-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,2-phenylenediamine (LH4) and glyoxal-bis(2-hydroxy-3,5-di-tert-butylanil) (L'H2), respectively, were synthesized and characterized. Single-crystal X-ray diffraction analysis showed that complexes 1 and 2 exhibit distorted pentagonal bipyramidal structures. These complexes contain a tetradentate, redox-active ONNO ligand that, doubly deprotonated, forms a dianion with a nearly planar core. The UV/vis/NIR absorption spectra of 1 and 2 demonstrate intense bands in the 500-1000 nm range attributed to intraligand charge transfer (ILCT). Electrochemical analysis demonstrates the redox-amphoteric properties of complexes 1 and 2. Complex 1 also exhibits efficient photothermal conversion (η = 57%) under 808 nm laser irradiation.

A series of penta-coordinate Cu(II) complexes were synthesised and structurally characterised to explore the relationship between coordinating environment, molecular magnetism, and antibacterial activities. A dinuclear complex, [Cu2(L1)2] (1), derived from an ONNO-coordinated tetradentate ligand (H2L1 = N,N'-bis[(3-methoxy-2-hydroxybenzylidene)]ethane-1,2-diamine), and three paramagnetic Cu(II) complexes, [Cu2(N3)2(L2)2] (2), [Cu(SCN)(L2)]n (3), and [Cu(CH3COO)(L2)]n (4), stabilised by a tridentate NNO-donor ligand (HL2 = (E)-1-(pyridin-2-yldiazenyl)naphthalen-2-ol), were isolated. Dinuclear complex 2 features an asymmetric end-on μ1,1-azido bridge, whereas 3 and 4 exhibit end-to-end μ1,3-thiocyanate/acetate bridges, forming one-dimensional polymeric architectures. Single-crystal X-ray diffraction confirmed their square-pyramidal molecular geometries. Complexes 1 and 4 exhibit field-induced single-molecule magnet (SMM) behaviour, consistent with quasi-isotropic S = ½ Cu(II) centres. All complexes show χMT ≈ 0.4 cm3 mol-1 K-1 with a slight decrease below 10 K. EPR parameters support the existence of mixed orbital character dz2/dx2-y2 (gx = 2.23, gy = 2.06, gz = 1.90) (1) and dx2-y2 (g∥ = 2.21, g⊥ = 2.06) (4) in the ground states. Molecular docking analyses demonstrated complex 3 has strong binding affinities against four biologically relevant targets: B-DNA (PDB ID: 1BNA), human DNA topoisomerase I (hTOPI, PDB ID: 1SC7), Escherichia coli MenB enzyme (EC-MenB, PDB ID: 3T88), and human serum albumin (HSA, PDB ID: 4LA0), indicating its potential for target-specific activity.

Background: Ceftriaxone (CF) shows high and wide range of the potent antibacterial activity with rare some side effects, a long half-life. Now new transition metal drug complex attract more attention for evolving of new capacities with multi-therapeutic approach such as anticancer activities. Methods: CF/Zinc (CF/Zn) complex was prepared and characterized via the transmission and scanning electron microscope. CF/Zn complex was prepared in (1:1) ceftriaxone: Zn+2 ratio. Result: (CF) coordinated as a tetradentate ligand towards zinc metal ion with the molecular formula [Zn(CF)(H2O)2].2H2O.The particle size and morphological surface for zinc complex was examined by using of many analyses: SEM, EDX, TEM, TGA/DTG and X-ray diffraction. This study investigated the effect of CF/Zn metal complex as a potent anticancer agent against three cancer cell lines (Breast adenocarcinoma MCF-7, Hepatocellular carcinoma HepG-2 and large cell lung cancer H460). The synthesized complex showed great anticancer capacities against the three cell lines at conc. 10 ug/ml and the living percentages were: 95.44, 90.6 and 94.04 µg/ml respectively and inhibited the proliferation of the cancer cells at conc.100 ug/ml and the living percentages were 90.35, 80.25 and 84.26 µg/ml. Exposure to CF/Zn complex even at very low concentrations elevated anticancer capacities of CF against three dangerous and common cancer types worldwide.

Ligand design plays a crucial role in developing chiral transition metal complexes with enhanced or new catalytic properties. Here, we report our progress toward a new class of linear tetradentate NCCN ligands incorporating strongly σ-donating carbene moieties. The NCCN ligand coordinates to iron(II) in a cis-α topology, with two pyridine donors occupying the apical positions and two 1,2,3-triazolin-5-ylidene mesoionic carbene (MIC) donors in the equatorial plane. Two acetonitrile ligands complete the octahedral coordination sphere, and their lability provides the basis for the observed catalytic activity. Notably, the two strongly σ-donating MIC groups create a strong ligand field, which is critical for achieving configurational stability of the metal-centered stereogenicity. This design strategy thus enabled the first chiral-at-iron catalyst derived from an achiral tetradentate ligand, which was applied to catalytic and enantioselective C(sp3)-H amination and a Cannizzaro reaction.