Search Results (39)

This study employs molecular dynamics simulations to investigate counterion effects (Li⁺, Na⁺, K⁺) on the interfacial aggregation of mixed short-chain fluorocarbon, Perfluorohexanoic acid (PFH_XA), and Sodium dodecyl sulfate (SDS) surfactants. Motivated by the need for greener surfactant alternatives and a fundamental understanding of molecular interactions governing their behavior, we demonstrate that counterion hydration radius critically modulates system organization. K⁺ ions induce superior monolayer condensation and interfacial performance compared to Li⁺ and Na⁺ counterparts, as evidenced by threefold analysis: (1) RMSD/MSD-confirmed equilibrium attainment ensures data reliability; (2) 1D/2D density profiles and surface tension measurements reveal K⁺-enhanced packing density (lower solvent-accessible surface area versus Na⁺ and Li⁺ systems); (3) Electrostatic potential analysis identifies synergistic complementarity between SDS’s hydrophobic stabilization via dodecyl chain interactions and PFH_XA’s charge uniformity, optimizing molecular-level charge screening. Radial distribution function analysis demonstrates K⁺’s stronger affinity for SDS head groups, with preferential sulfate coordination reducing surfactant-water hydration interactions. This behavior correlates with hydrogen-bond population reduction, attributed to SDS groups functioning as multidentate ligands—their tetrahedral oxygen arrangement facilitates cooperative hydrogen-bond networks, while counterion-specific charge screening competitively modulates bond formation. The resultant interfacial restructuring enables ordered molecular arrangements with lower system curvature than those observed in Li⁺ and Na⁺-containing systems. These findings elucidate counterion-mediated interfacial modulation mechanisms and establish K⁺ as an optimal candidate for enhancing PFH_XA/SDS mixture performance through hydration-radius screening. The work provides molecular-level guidelines for designing eco-friendly surfactant systems with tailored interfacial properties. Full article

2-Hydroxy-3-methoxybenzaldehyde semicarbazone (HMBS) is a multidentate ligand with interesting coordination behavior that depends on the central metal ion and the overall complex geometry. In this contribution, the structural characteristics of five HMBS-containing complexes with different metal ions (Dy, Er, Ni, and V) were investigated. Four binuclear and one mononuclear complex were selected from the Cambridge Structural Database. The crystallographic structures and intermolecular interactions in the solid state were analyzed, and the effect of central metal ions was elucidated. The different contributions of the most numerous contacts were explained by examining additional ligands in the structure. Density functional theory (DFT) optimizations were performed for the selected complexes, and the applicability of different computational methods was discussed. The Quantum Theory of Atoms in Molecules (QTAIMs) approach was employed to identify and quantify interactions in nickel and vanadium complexes, highlighting the role of weak intermolecular interactions between ligands in stabilizing the overall structure. Molecular docking studies of the interaction between these complexes and Human Serum Albumin (HSA) demonstrated that all compounds bind within the active pocket of the protein. The overall size and presence of aromatic rings emerged as key factors in the formation of stabilizing interactions. Full article

Multidentate bispidine ligands, including tetra-, penta-, hexa-, hepta-, and octadentate variants, exhibit strong coordination tendencies due to their intrinsic rigidity, significant reorganization potential, and ability to efficiently encapsulate metal ions. These structural attributes profoundly influence the thermodynamic stability, metal ion selectivity, redox behavior, and spin-state configuration of the resulting complexes. Metal ions, in turn, serve as highly suitable candidates for coordination due to their remarkable kinetic inertness, rapid complex formation kinetics, and low redox potential. This review focuses on ligands incorporating the bispidine core (3,7-diazabicyclo[3.3.1]nonane) and provides an overview of advancements in the synthesis of metal complexes involving p-, d-, and f-block elements. Furthermore, the rationale behind the growing interest in bispidine-based complexes for applications in radiopharmaceuticals, medicinal chemistry, and organic synthesis is explored, particularly in the context of their potential for diagnostic and catalytic drug development. Full article

A first syn-type tricyclic 8-8-8 (three fused-8-membered ring) laddersiloxane functionalized with four azido groups was successfully synthesized through efficient and highly selective hydrosilylation and nucleophilic substitution, achieving an excellent overall yield. The starting material, a tetravinyl-substituted 8-8-8 laddersiloxane, was prepared via a straightforward and scalable method. The obtained azido-functionalized ladder compound, fully characterized, constitutes a versatile building block for hybrid materials. Reacting this compound with 2-ethynylpyridine via click chemistry yielded a multidentate ligand containing four 2-triazole-pyridyl moieties. This N,N-bidentate ligand was subsequently employed in copper-catalyzed alcohol oxidative dehydrogenation reactions, demonstrating its potential in catalysis. Full article

We report the research results of polynuclear complexes consisting of 3d-4f mixed-metal cores that are maintained by acetate ligands and multidentate Schiff base ligands with structurally exposed thioether groups. The presence of the latter at the periphery of these neutral compounds enables their anchoring onto substrate surfaces. Specifically, we investigated the electronic and magnetic properties as well as the structural arrangement in {Mn^II₃Mn^IVLn^III₃} with Ln = Dy, Yb coordination complexes using various complementary methods. We studied the electronic and atomic structure of the target compounds using the XAS and XES techniques. The molecular structures of the compounds were determined using density functional theory, and the magnetic data were obtained as a function of the magnetic field. Using the XMCD method, we followed the changes in the electronic and magnetic properties of adsorbed magnetic compounds induced by the reaction of ligands through interaction with the substrate. The complexes show antiferromagnetic exchange interactions between Mn and Ln ions. The spectroscopic analyses confirmed the structural and electronic integrity of complexes in organic solution. This study provides important input for a full understanding of the dependence of the magnetic properties and the molecule–substrate interaction of single adsorbed molecules on the type of ligands. It highlights the importance of chemical synthesis for controlling and tailoring the magnetic properties of metalorganic molecules for their use as optimized building blocks of future molecular spin electronics. Full article

Three amidine-based ligands were used in the crystal design of a series of mononuclear Zn(II) complexes. Interaction of zinc chloride, ZnCl₂, with N-2-pyridylimidoyl-2-pyridylamidine (Py₂ImAm) resulted in complexes [Zn(Py₂ImAm)₂] (1) and [ZnCl₂(Py₂ImAm)] (2). In [Zn(Py₂ImAm)₂] (1, monoclinic, P2₁/c), the metal ion was coordinated with the bidentate pocket of the anionic form of Py₂ImAm, while in [ZnCl₂(Py₂ImAm)] (2, monoclinic, P2₁/n), the tridentate coordination to a neutral Py₂ImAm was completed by two chloride anions. This structural variation was achieved by a pH-controlling strategy using the weak base triethylamine (TEA). Otherwise, three ionic complexes were obtained with 2-amidinopyridine (PyAm) and Zinc(II), [ZnCl(PyAm)₂]Cl (3, triclinic, P-1), [ZnCl(PyAm)₂]₂[ZnCl₄]·C₂H₅OH (4, monoclinic, P2₁/n), and [ZnCl(PyAm)₂]₂Cl·CH₃OH (5, triclinic, P-1). They comprised the same [ZnCl(PyAm)₂]⁺ monocation with a butterfly-like shape provided by the bidentate chelate coordination of two PyAm neutral entities and a chloride ligand. In a similar butterfly shape, ionic complex [ZnCl(PmAm)₂]₂[ZnCl₄] (6, monoclinic, C2/c) comprised the mononuclear [ZnCl(PmAm)₂]⁺ cations with two bidentate chelate-coordinated 2-amidinopyrimidine (PmAm) as neutral ligands. The Zn(II) pentacoordinated arrangement in 3–6 was variable, from square pyramidal to trigonal bipyramidal. The reported compounds’ synthetic protocols, crystal structures and photoluminescence properties are discussed. Full article

Trinuclear metallacyclic oxidovanadium(V) complexes, [{VO(L³⁺²R)}₃] (1–3) with asymmetric multidentate linking ligands (H₃L³⁺²R: R = H, Me, Br), were synthesized. The molecular structure of 1 is characterized as a tripod structure, with each V(V) ion coordinated by ONO-atoms from a tridentate Schiff base site and ON-atoms from a bidentate benzoxazole site of two respective H₃L³⁺²H ligands. The intramolecular V⋯V distances range from 8.0683 to 8.1791 Å. Complex 4 is a mononuclear dioxidovanadium(V) complex, (Et₃NH)[VO₂(HL³⁺²H)]. Cyclic voltammograms of 1−3 in DMF revealed redox couples attributed to three single-electron transfer processes. Full article

The aerobic photooxidation of sulfides into sulfoxides in eco-friendly solvents, notably water, at room temperature, represents a significant interest in the domain of synthetic chemistry. This study introduces four highly stable hexadentate Ir(III) complexes: [Ir(fpqen)](PF₆) (1), [Ir(btqen)](PF₆) (2), [Ir(bmpqen)](PF₆) (3), and [Ir(bnqen](PF₆) (4) (where bfpqen is N,N′-bis(2-(4-fluorophenyl)quinolin-8-yl)ethane-1,2-diamine, btqen is N,N′-bis(2-(4-tolyl)quinolin-8-yl)ethane-1,2-diamine, bmpqen is N,N′-bis(2-(4-methoxyphenyl)quinolin-8-yl)ethane-1,2-diamine, and bnqen is N,N′-bis(2-naphthylquinolin-8-yl)ethane-1,2-diamine). These complexes were synthesized utilizing an in situ inter-ligand C-N cross-coupling photoreaction of the precursors [Ir(L)₂(en)](PF₆) (L is 2-(4-fluorophenyl)quinoline, (2-(4-tolyl)quinoline, 2-(4-methoxyphenyl)quinoline or 2-naphthylquinoline, and en is 1,2-diamine) under benign conditions. This methodology furnishes a valuable and complementary approach for the in situ generation of multidentate complexes through a post-coordination inter-ligand-coupling strategy under mild conditions. Moreover, these hexadentate Ir(III) complexes exhibit pronounced catalytic activity and chemo-selectivity toward the aerobic photooxidations of sulfides into sulfoxides in aqueous media at room temperature, offering a new avenue for the sustainable synthesis of sulfoxides. Full article

A series of reported Pt(II) carbene complexes possibly have the ability to serve as the new generation of blue emitters in luminescent devices because of their narrow emission spectra, high photoluminescence quantum yields (PLQYs), and rigid molecular skeleton. However, the combination of all carbene ligands with different multidentate structures will affect the overall planarity and horizontal dipole ratio to varying degrees, but the specific extent of this effect has not previously been analyzed in detail. In this work, density functional computation is used to study a class of platinum tetracarbene bidentate complexes with similar absorption and emission band characteristics, which is the main reason for the remarkable difference in quantum efficiency due to subtle differences in electronic states caused by different ligands. From the calculation results, the major reason, which results in significantly decrease in quantum efficiency for [Pt(cyim)₂]²⁺, is that [Pt(cyim)₂]²⁺ can reach the non-radiative deactivation metal-centered d-d excited state through an easier pathway compared with [Pt(meim)₂]²⁺. The result, based on changes in the dihedral angle between ligands, can achieve the goal of improving and designing materials by adjusting the degree of the dihedral angle. (meim: bis(1,1′-dimethyl-3,3′-methylene-diimidazoline-2,2′-diylidene); cyim: bis(1,1′-dicyclohexyl-3,3′-methylene-diimidazoline-2,2′-diylidene). Full article

A novel strategy for the separation of cadmium from base metals in chloride medium by anion exchange based on the formation of cadmium halo-complexes is presented in this article. Instead of using excess Br⁻ or I⁻ in the feed solution, the anion exchange resin or fibre was first preloaded with Br⁻ or I⁻ for Cd²⁺ adsorption from Cl⁻ solution. Thus, the consumption of iodide or bromide was minimized while promising high adsorption stability of Cd²⁺. The adsorption thermodynamics and kinetics of Cd²⁺ were studied. The adsorption thermodynamics results were processed with Langmuir and Freundlich models and adsorption kinetics results were treated with Pseudo first order model, Pseudo second order model and intraparticle diffusion model. The adsorption mechanism was studied with the aid of FTIR and elemental analysis. Three strategies were applied for the stripping of Cd²⁺, including the use of water for disequilibrating its halo-complex formation, the formation of positively charged species with ammonia, and the formation of positively charged chelate with multidentate ligand ethylenediamine. On the bases of these results, separation performance was investigated with strongly basic anion exchange resin and fibre, and it was shown that Cd²⁺ can be efficiently separated from base metals in a wide range of acidity, and that pure Cd²⁺ solution can be obtained, thus providing a robust, environmentally friendly, and economic technology for its separation. Full article

The coordination ability of the pyridine derivative of cyclic triimidazole, namely 3-(pyridin-2-yl)triimidazotriazine (TT-Py) towards Cu(I) was explored. TT-Py is an appealing nitrogen-rich ligand characterized by the presence of three imidazole nitrogen atoms with trigonal symmetry and a pyridine moiety, available for coordination to metal ions. The multidentate nature of TT-Py allows to isolate, by reaction with CuI at room temperature, the one-dimensional coordination network [Cu₂I₂(TT-Py)]_n (1). 1 is characterized by a rare structural network built-up by the combination in a 1:2 ratio of two common motifs for Cu(I) halides coordination polymers, which are the double-stranded stair and the zig-zag chain. 1 displays one broad long-lived emission in the solid state, which has been associated, by the support of DFT and TDDFT calculation, with low-energy transitions of MLCT or XMLCT character. Full article

A mixture of 2-pyridine carboxaldehyde, 4-formylimidazole (or 2-methyl-4-formylimidazole), and NiCl₂·6H₂O in a molar ratio of 2:2:1 was reacted with two equivalents of hydrazine monohydrate in methanol, followed by the addition of aqueous NH₄PF₆ solution, afforded a Ni^II complex with two unsymmetric azine-based ligands, [Ni(HL^H)₂](PF₆)₂ (1) or [Ni(HL^Me)₂](PF₆)₂ (2), in a high yield, where HL^H denotes 2-pyridylmethylidenehydrazono-(4-imidazolyl)methane and HL^Me is its 2-methyl-4-imidazolyl derivative. The spectroscopic measurements and elemental analysis confirmed the phase purity of the bulk products, and the single-crystal X-ray analysis revealed the molecular and crystal structures of the Ni^II complexes bearing an unsymmetric HL^H or HL^Me azines in a tridentate κ³N, N’, N” coordination mode. The HL^H complex with a methanol solvent, 1·MeOH, crystallizes in the orthorhombic non-centrosymmetric space group P2₁2₁2₁ with Z = 4, affording conglomerate crystals, while the HL^Me complex, 2·H₂O·Et₂O, crystallizes in the monoclinic and centrosymmetric space group P2₁/n with Z = 4. In the crystal of 2·H₂O·Et₂O, there is intermolecular hydrogen-bonding interaction between the imidazole N–H and the neighboring uncoordinated azine-N atom, forming a one-dimensional polymeric structure, but there is no obvious magnetic interaction among the intra- and interchain paramagnetic Ni^II ions. Full article

Mixed multidentate linkers with donor groups of different types can be fruitfully exploited in the self-assembly of coordination polymers (CPs) and Metal-Organic Frameworks (MOFs). In this work we develop new ligands containing a β-diketone chelating functionality, to better control the stereochemistry at the metal center, and tetrazolyl multidentate bridging groups, a combination not yet explored for networking with metal ions. The new ligands, 1,3-bis(4-(1H-tetrazol-5-yl)phenyl)-1,3-propanedione (H₃L¹) and 1-phenyl-3-(4-(1H-tetrazol-5-yl)phenyl)-1,3-propanedione (H₂L²), are synthesized from the corresponding nitrile precursors by [2+3] dipolar cycloaddition of azide under metal-free catalytic conditions. Crystal structure analysis evidences the involvement of tetrazolyl fragments in multiple hydrogen bonding giving 2D and 1D supramolecular frameworks. Reactivity of the new ligands with different metal salts indicates good coordinating ability, and we report the preparation and structural characterization of the tris–chelate complex [Fe(HL¹)₃]³⁻ (1) and the homometallic 2D CP [ZnL²(DMSO)] (2). In compound 1 only the diketonate donor is used, whereas the partially deprotonated tetrazolyl groups are involved in hydrogen bonding, giving rise to a 2D supramolecular framework of (6,3)IIa topological type. In compound 2 the ligand is completely deprotonated and uses both the diketonate donor (chelating) and the tetrazolate fragment (bridging) to coordinate the Zn(II) ions. The resulting neutral 2D network of sql topology shows luminescence in the solid state, which is red shifted with respect to the free ligand. Interestingly, it can be easily exfoliated in water to give a luminescent colloidal solution. Full article

The reaction of MnCl₂, 2-(5-{6-[5-(Pyrazin-2-yl)-1H-1,2,4-triazol-3-yl]pyridin-2-yl}-1H-1,2,4-triazol-3-yl)pyrazine (H₂ptptp), 4,4′-sulfonyldibenzoic acid (H₂sdba) or 4-(4-carboxyphenoxy)phthalate acid (H₃cpop) and [BMI]Br ionic liquids (BMI = 1-butyl-3-methylimidazolium) gave rise to two complexes, {[Mn₄(ptptp)₂(sdba)₂(H₂O)₂]·2H₂O}_n (1) and {[Mn₃(ptptp)(cpop)Br(H₂O)₂]·2H₂O}_n (2). The compounds have been well characterized by elemental analysis, IR spectra, thermogravimetric analysis, as well as single-crystal and powder X-ray diffraction. The structure feature of 1 is that Mn(II) ions in the [Mn₆(sdba)₂] loops of V-shaped sdba²⁻ ligands are ptptp²⁻ ligands, respectively, and a 2D layer is constructed from sdba²⁻ and ptptp²⁻ ligands. The adjacent 2D layers are connected by O–H⋯N hydrogen bonds to form a 3D supramolecular network. The neighbouring trinuclear Mn(II) clusters in 2 are linked by V-shaped cpop³⁻ ligands to give a 2D layer, which is penetrated by ptptp²⁻ ligands to form self-threading structure. The results of variable-temperature magnetic studies have shown that the magnetic interactions between the Mn(II) ions in 1 and 2 are mainly due to antiferromagnetic coupling. Full article

Microbial biofilms are represented by sessile microbial communities with modified gene expression and phenotype, adhered to a surface and embedded in a matrix of self-produced extracellular polymeric substances (EPS). Microbial biofilms can develop on both prosthetic devices and tissues, generating chronic and persistent infections that cannot be eradicated with classical organic-based antimicrobials, because of their increased tolerance to antimicrobials and the host immune system. Several complexes based mostly on 3D ions have shown promising potential for fighting biofilm-associated infections, due to their large spectrum antimicrobial and anti-biofilm activity. The literature usually reports species containing Mn(II), Ni(II), Co(II), Cu(II) or Zn(II) and a large variety of multidentate ligands with chelating properties such as antibiotics, Schiff bases, biguanides, N-based macrocyclic and fused rings derivatives. This review presents the progress in the development of such species and their anti-biofilm activity, as well as the contribution of biomaterials science to incorporate these complexes in composite platforms for reducing the negative impact of medical biofilms. Full article