Search Results (24)

Reactive oxygen species (ROS)-mediated cancer therapy has attracted extensive attention due to its high spatiotemporal selectivity and minimal side effects. Herein, we report a nonanuclear Pd-based coordination cage of Pd₆-TMPP(Ni), constructed from Ni-chelated TMPP(Ni) as the metalloligand and Pd²⁺ ions (H₂TMPP = meso-tetrakis (6-methylpyridin-3-yl) porphyrin). Pd₆-TMPP(Ni) integrates dual ROS-generation for cancer therapy, viz., hydroxyl radical (•OH) production and photoinduced singlet oxygen (¹O₂) generation. In vitro cytotoxicity assays against cancer cell lines NCI-H82 (lung cancer), A549 (lung cancer), KYSE-510 (esophageal cancer), and Te-1 (esophageal cancer) reveal its potent dark toxicity (IC₅₀: 1.9–2.1 μmol L⁻¹) and phototoxicity (IC₅₀: 0.8–1.5 μmol L⁻¹), which is attributed to enhanced intracellular ROS accumulation. This work develops a versatile therapeutic platform that harnesses Ni-induced •OH for chemodynamic therapy (CDT) and porphyrin-generated ¹O₂ for photodynamic therapy (PDT), thereby mitigating the oxygen dependence of conventional PDT. Full article

In this publication, the potential non-gadolinium magnetic resonant imaging agent—nanoparticulate K₂Mn[Fe(CN)₆]—its comparison sample KFe[Co(CN)₆], as well as their reference samples were measured and analyzed using Mn, Co and Fe L-edge X-ray absorption spectroscopy (L XAS). From the information obtained, we conclude that K₂Mn[Fe (CN)₆] has a high spin (hs)-Mn(II) and a low spin (ls)-Fe(II), while KFe[Co(CN)₆] has an hs-Fe(II) and an ls-Co(III). In these Prussian blue (PB) analog structures, the L XAS analysis also led to the conclusion that the hs-Mn(II) in K₂Mn[Fe(CN)₆] or the hs-Fe(II) in KFe[Co(CN)₆] bonds to the N in the [M(CN)₆]^4−/3− ions (where M = Fe(II) or Co(III)), while the ls-Fe(II) in K₂Mn[Fe(CN)₆] or the ls-Co(III) in KFe[Co(CN)₆] bonds to the C in the [M(CN)₆]^4−/3− ion, suggesting the complexed metalloligand [Mn(II) or Fe(II)] occupies the N-bound site in PB. Then, nuclear resonant vibrational spectroscopy (NRVS) was used to confirm the results from the L XAS measurements: the Mn(II), Eu(III), Gd(III), Fe(II) cations complexed by [M(CN)₆]ⁿ⁻-metalloligand all take the N-bound site in PB-like structures. Our NRVS studies also prove that iron in the K₂Mn[Fe(CN)₆] compound has a 2+ oxidation state and is surrounded by the C donor atoms in the [M(CN)₆]ⁿ⁻ ions. Full article

We studied the synthesis and crystal structures of a new two-dimensional (2D) coordination polymer, {Fe^II(1-Ethyl-imidazole)₂[Ni^II(CN)₄]}_n (1), and one-dimensional (1D) coordination polymers, {Fe^II(1-benzyl-imidazole)₄[Ni^II(CN)₄]}_n (2) and {Fe^II(1-Allyl-imidazole)₄[Ni^II(CN)₄]}_n (3). Compound 1 has a 2D sheet structure, which is a traditional Hofmann-like structure. In compound 1, an octahedral Fe^II ion is coordinated with the nitrogen atoms of the [Ni^II(CN)₄] planar unit at equatorial positions and monodentate imidazole derivatives at axial positions. The layers construct a parallel stacking array. Compounds 2 and 3 have a 1D chain structure. In compounds 2 and 3, the Fe^IIN₆ coordination environment is formed with four imidazole ligands and two [Ni^II(CN)₄]²⁻ metalloligands. In the [Ni^II(CN)₄]²⁻ unit, two CN substituents act as bidentate ligands that form infinite –Ni–C–N–Fe–N–C–Ni– chains. Herein, we discuss the systematic design of polymeric dimensionality. Full article

A new mixed-valence one-dimensional coordination polymer of formula {[Co^II(MeOH)₂][(μ-NC)₂Co^III(dmphen)(CN)₂]₂}_n·2nH₂O (1) was obtained by reacting the Ph₄P[Co^II(dmphen)(CN)₃] metalloligand (dmphen = 2,9-dimethyl-1,10-phenanthroline and Ph₄P⁺ = tetraphenylphosphonium ion) with cobalt(II) acetate tetrahydrate. The structural analysis shows the formation of a neutral 4,2-ribbon-like chain of vertex-sharing cyanido-bridged {Co^III₂Co^II₂} squares in which the metalloligand underwent an oxidation process and a reorganization to form {Co^III(dmphen)(CN)₄}⁻ linkers that coordinate to the [Co^II(MeOH)₂]²⁺ units through single cyanido ligands. Both cobalt(II) and Co(III) cations are six-coordinated in distorted octahedral environments. The shortest intrachain distance between the paramagnetic cobalt(II) ions is 7.36 Å, a value which is shorter than the shortest interchain one (10.36 Å). Variable-temperature (1.9–300 K) static (dc) magnetic measurements for 1 indicate the occurrence of magnetically isolated high-spin cobalt(II) ions with a D value of +67.0 cm⁻¹. Dynamic alternating current (ac) magnetic measurements between 2.0–13 K reveal that 1 exhibits slow magnetic relaxation under non-zero applied dc fields, being thus a new example of field-induced SIM with easy-plane magnetic anisotropy. Theoretical calculations by CASSCF/NEVPT2 on 1 support the results from magnetometry. The relaxation of the magnetization occurs in the ground state under external dc fields through a two-phonon Raman process and one intra-Kramers mechanism. Full article

We present five new dinuclear triple helicate compounds of types [Mn₂L₃](ClO₄)₄, [Co₂L₃](BF₄)₄, [Ni₂L₃](BF₄)₄, [Cu₂L₃](BF₄)₄, and [Zn₂L₃](BF₄)₄, where L is a previously reported semi-rigid ligand incorporating two α-diimine primary donor groups and two secondary 4-pyridyl donor groups. All complexes have been characterized in both solution and the solid state. Single crystal X-ray diffraction studies were used to probe the variation in the respective helical structures as the coordinated metal ion was altered, including the effect on the orientations of the secondary binding domains. The influence of the metal ion size, the spin state in the case of Fe(II), and the presence of Jahn-Teller distortions on the overall helical structure has been investigated. These results form a basis for the design and construction of new large metallosupramolecular architectures which manifest properties associated with the constituent helical metalloligand units. Full article

This review is devoted to an analysis of currently known heterometallic molecular magnets based on an orbitally degenerate 5d metalloligand, [Re^IV(CN)₇]³⁻. Heptacyanidometallates with a pentagonal bipyramidal structure of the coordination site and degenerate ground spin state are the source of anisotropic magnetic exchange interactions upon the formation of cyanide-bonded assemblies involving the paramagnetic complexes of the first transition series. Therefore, the development of methods for chemical design using such molecular magnetic modules is extremely important. If for the 4d congener, isoelectronic [Mo^III(CN)₇]³⁻, a family of approximately 40 heterometallic compounds, was obtained, whereas for heptacyanorhenate(IV), no more than 20 are known. However, as a result of recent studies, heterobimetallic magnetic assemblies of all dimensionalities have been synthesized, from 0D to 1D, demonstrating slow magnetization relaxation, to 2D networks and 3D frameworks possessing large magnetic hysteresis. The most anisotropic is a 2D network, PPN[{Mn^III(acacen)}₂Re^IV(CN)₇]·Solv, with a critical temperature of 20 K and magnetic hysteresis with a record coercivity for cyanide-bridged molecular materials. Full article

Three new layered mixed metal phosphonates [CoMg(notpH₂)(H₂O)₂]ClO₄·nH₂O (CoMg·nH₂O), [Co₂Sr₂(notpH₂)₂(H₂O)₅](ClO₄)₂·nH₂O (CoSr·nH₂O), and [CoBa(notpH₂)(H₂O)_1.5]ClO₄ (CoBa) were synthesized by reacting a tripodal metalloligand Co^III(notpH₃) [notpH₆ = C₉H₁₈N₃(PO₃H₂)₃] with alkaline earth metal ions. Along with an increase in the radius of the alkaline earth metal ions, the 6-coordinate {MgO₆}, 7-coordinate {SrO₇}, and 9-coordinate {BaO₉} geometries are the distorted octahedron, capped triangular prism, and tricapped triangular prism, respectively. Consequently, the metalloligand Co(notpH₂)⁻ adopts variable coordination modes to bind the alkaline earth metal nodes, forming diverse layer topologies in the three mixed metal phosphonates. The AC impedance measurements revealed that the proton conductivities at 25 °C and 95% relative humidity (RH) follow the sequence: CoMg·nH₂O > CoSr·nH₂O > CoBa. As expected, CoMg·nH₂O exhibits a 28-fold enhanced value for proton conductivity (4.36 × 10⁻⁴ S cm⁻¹) compared with the previously reported isostructural compound, CoCa·nH₂O, at 25 °C and 95% RH due to the greater Lewis acid strength of Mg(II) lowering the pKa of the coordinated water. Full article

The use of two triazine-derived pincer ligands led to the obtaining of a heterometallic compound and of an unexpected 3D coordination polymer (CP). Therefore, by reacting 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tptz) with Zn(NO₃)₂ and K[Ag(CN)₂], the cyanido-bridged [Ag(CN)(m-CN)]₂[Zn(tptz)(H₂O)] (1) trinuclear complex was formed. Compound 1 crystallizes in the orthorhombic polar space group Aea2 and the crystal packing involves argentophilic interactions. When 2,4,6-Tris(2-pyrimidyl)-1,3,5-triazine (TPymT) was used as a ligand, along with the same precursors as for 1, a 3D CP was assembled, [Ag₆(CN)₆(TPymT)₂] (2). The formation of 2 was favored, most likely, by the dicyanoargentate(I) ion dissociation and its interesting topology is due to the bridging cyanide ligands and argentophilic interactions. The fluorescence of both compounds was studied and compared to the emission features of their ligands. For the two coordination compounds, ligand-centered fluorescence data are discussed. Full article

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 E_1/2 = 1.133 V vs. SHE. Furthermore, the polymeric Fe^II 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. Full article

The design of new metallocage polyhedra towards pre-determined structures can offer both practical as well as intellectual challenges. In this mini-review we discuss a selection of recent examples in which the use of the metalloligand approach has been employed to overcome such challenges. An attractive feature of this approach is its stepwise nature that lends itself to the design and rational synthesis of heterometallic metal–organic cages, with the latter often associated with enhanced functionality. Full article

CuAAC (Cu catalyzed azide-alkyne cycloaddition) click-reaction is a simple and powerful method for the post-synthetic modification of organometallic complexes of transition metals. This approach allows the selective introduction of additional donor sites or functional groups to the periphery of the ligand environment. This is especially important if a metalloligand with free donor sites, which are of the same nature as the primary site for the coordination of the primary metal, has to be created. The concept of post-synthetic modification of organometallic complexes by click-reaction is relatively recent and the currently available experimental material does not yet allow us to identify trends and formulate recommendations to address specific problems. In the present study, we have applied the CuAAC reaction for the post-synthetic modification of diimine mononuclear complexes Re(I), Pt(II) and Ir(III) with C≡C bonds at the periphery of the ligand environment and demonstrated that click-chemistry is a powerful tool for the tunable chemical post-synthetic modification of coordination compounds. Full article

Polynuclear heterobimetallic coordination cages in which different metal cations are connected within a ligand scaffold are known to adopt a variety of polyhedral architectures, many of which display interesting functions. Within the extensive array of coordination cages incorporating Fe(II) centres reported so far, the majority contain low-spin (LS) Fe(II), with high-spin (HS) Fe(II) being less common. Herein, we present the synthesis and characterisation of a new tetradecanuclear heterobimetallic [Fe₈Pd₆L₈](BF₄]₂₈ (1) cubic cage utilising the metalloligand approach. Use of the tripodal tris-imidazolimine derivative (2) permitted the formation of the tripodal HS Fe(II) metalloligand [FeL](BF₄)₂·CH₃OH (3) that was subsequently used to form the coordination cage 1. Magnetic and structural analyses gave insight into the manner in which the HS environment of the metalloligand was transferred into the cage architecture along with the structural changes that accompanied its occupancy of the eight corners of the discrete cubic structure. Full article

One of the pathways toward luminescent single-molecule magnets (SMMs) is realized by the self-assembly of lanthanide(3+) ions with cyanido transition metal complexes. We report a novel family of emissive SMMs, {Yb^III(4-pyridone)₄[Fe^II(phen)₂(CN)₂]₂}(CF₃SO₃)₃·solv (solv = 2MeCN, 1·MeCN; 2AcrCN, 1·AcrCN; 2PrCN, 1·PrCN; 2MalCN·1MeOH; 1·MalCN; MeCN = acetonitrile, AcrCN = acrylonitrile, PrCN = propionitrile, MalCN = malononitrile). They are based on paramagnetic Yb^III centers coordinating diamagnetic [Fe^II(phen)₂(CN)₂] metalloligands but differ in the nitrile solvents of crystallization. They exhibit a field-induced slow magnetic relaxation dominated by a Raman process, without an Orbach relaxation as indicated by AC magnetic data and the ab initio calculations. The Raman relaxation is solvent-dependent as represented by the power “n” of the B_RamanTⁿ contribution varying from 3.07(1), to 2.61(1), 2.37(1), and 1.68(4) for 1·MeCN, 1·PrCN, 1·AcrCN, and 1·MalCN, respectively, while the B_Raman parameter adopts the opposite trend. This was correlated with the variation of phonon modes schemes, including the number of available vibrational modes and their energies, dependent on the increasing complexity of the applied nitrile. 1·MeCN and 1·MalCN show the additional T-independent relaxation assignable to dipole-dipole interactions as confirmed by its suppression in 1·AcrCN and 1·PrCN revealing longer Yb–Yb distances and the disappearance in the Lu^III-diluted 1·MeCN@Lu. All compounds exhibit Yb^III–centered near-infrared photoluminescence sensitized by organic ligands. Full article

Three new 1D cyanido-bridged 3d-4f coordination polymers, {[Gd(L)(H₂O)₂Fe(CN)₆]·H₂O}_n (1_GdFe), {[Dy(L)(H₂O)₂Fe(CN)₆]·3H₂O}_n (2_DyFe), and {[Dy(L)(H₂O)₂Co(CN)₆]·H₂O}_n (3_DyCo), were assembled following the building-block approach (L = pentadentate bis-semicarbazone ligand resulting from the condensation reaction between 2,6-diacetyl-pyridine and semicarbazide). The crystal structures consist of crenel-like Ln^III-M^III alternate chains, with the Ln^III ions connected by the hexacyanido metalloligands through two cis cyanido groups. The magnetic properties of the three complexes have been investigated. Field-induced slow relaxation of the magnetization was observed for compounds 2_DyFe and 3_DyCo. Compound 3_DyCo is a new example of chain of Single Ion Magnets. Full article

Three new heterometallic [Cr^III₈Ni^II₆] coordination cubes of formulae [Cr^III₈Ni^II₆L₂₄(H₂O)₁₂](NO₃)₁₂ (1), [Cr^III₈Ni^II₆L₂₄(MeCN)₇(H₂O)₅](ClO₄)₁₂ (2), and [Cr^III₈Ni^II₆L₂₄Cl₁₂] (3) (where HL = 1-(4-pyridyl)butane-1,3-dione), were synthesised using the paramagnetic metalloligand [Cr^IIIL₃] and the corresponding Ni^II salt. The magnetic skeleton of each capsule describes a face-centred cube in which the eight Cr^III and six Ni^II ions occupy the eight vertices and six faces of the structure, respectively. Direct current magnetic susceptibility measurements on (1) reveal weak ferromagnetic interactions between the Cr^III and Ni^II ions, with J_Cr-Ni = + 0.045 cm⁻¹. EPR spectra are consistent with weak exchange, being dominated by the zero-field splitting of the Cr^III ions. Excluding wheel-like structures, examples of large heterometallic clusters containing both Cr^III and Ni^II ions are rather rare, and we demonstrate that the use of metalloligands with predictable bonding modes allows for a modular approach to building families of related polymetallic complexes. Compounds (1)–(3) join the previously published, structurally related family of [M^III₈M^II₆] cubes, where M^III = Cr, Fe and M^II = Cu, Co, Mn, Pd. Full article