Multinuclear Compounds Research Articles

Synthesis, molecular modeling and preliminary anticancer evaluation of 2-ferrocenylbenzimidazole metallofragments

The synthesis of 2-ferrocenylbenzimidazole metallofragments, with varying substituents in the 5-position of a benzimidazole scaffold is described. This strategy involves linking bioactive multinuclear compounds with known pharmacophores with the potential to interact with protein targets. To further understand the interactions of multinuclear complexes with proteins, in silico simulations were performed by employing protein models of common cancer therapeutic targets to predict their affinity to bind to these proteins. The trinuclear complexes show higher affinities and superior binding energies over monomeric congeners. The synthesized compounds were screened for their cytotoxic activity against two breast cancer cell lines, and selected compounds showed moderate activity. These results suggest that the conjugation of the ferrocene moiety to the benzimidazole motif presents a valuable strategy in the design of organometallic compounds for anticancer chemotherapy.

Keep it tight: a crucial role of bridging phosphine ligands in the design and optical properties of multinuclear coinage metal complexes.

Copper subgroup metal ions in the +1 oxidation state are classical candidates for aggregation via non-covalent metal-metal interactions, which are supported by a number of bridging ligands. The bridging phosphines, soft donors with a relatively labile coordination to coinage metals, serve as convenient and essential components of the ligand environment that allow for efficient self-assembly of discrete polynuclear aggregates. Simultaneously, accessible and rich modification of the organic spacer of such P-donors has been used to generate many fascinating structures with attractive photoluminescent behavior. In this work we consider the development of di- and polynuclear complexes of M(i) (M = Cu, Ag, Au) and their photophysical properties, focusing on the effect of phosphine bridging ligands, their flexibility and denticity.

Synthesis and Characterization of HgII/Se/CuI Multinuclear Compounds from Mercury(II) Bis(p‐aminobenzeneselenolate) – Hg(SeC6H4NH2‐p)2

In this paper we explore an amino functionalized selenolate unit for the synthesis of new multinuclear compounds with promising interesting properties and potential precursors of semiconductors. We present for the first time the X‐ray crystallographic structure of [Hg(SeC6H4NH2)2]2·diox (1·diox) and its copper(I) derivatives: HgCu2X2(SeC6H4NH2)2(PPh3)4·4diox [X = Br (2·4diox) and I (3·4diox)]. The compounds 1 and 2, 3 can be considered as the starting material and intermediates, respectively, for the synthesis of ternary HgII/Se/CuI nanoclusters. We also provide IR and NMR spectroscopic data and evaluate the optical features of these compounds by difuse reflectance UV/Vis spectroscopy.

Multinuclear compounds of s-elements with sterically hindered о-semiquinonates and catecholates

Alkali metals form mutinuclear compounds with redox-active singly and doubly reduced derivatives of sterically of hindered о-benzoquinones. Complexes [Na6(Cat)3(THF)7]•4THF, [Na5(Cat)2(SQ)(THF)5], [Na4(SQ)4(THF)4]•THF•C6H14, [Na4(3,5-SQ)4(THF)4], [K4(SQ)4(THF)4]•4THF and [Li3(SQ)3(THF)3]•THF (Cat is catecholate, SQ is semiquinonate) possessing high sensitivity to atmospheric oxygen were synthesized and their structures were determined. Magnetochemical measurements and quantum chemical calculations revealed that variation of the alkali metal and/or change in the structure of the polymetallic core significantly affect the energy of exchange interaction between the unpaired electrons of the paramagnetic ligands framing the polynuclear metal core formed by s-elements.

A novel octanuclear nickel(II)-molybdenum(VI) heterometallic cluster based on the salicylhydroxamate ligand.

Salicylhydroxamic acid (H3shi) is known for its strong coordination ability and multiple coordination modes, and can easily coordinate to metal cations to form compounds with five- or six-membered rings, as well as mono-, di- and multinuclear compounds with interesting structures having potential applications in organic chemistry, coordination chemistry, and the materials and biological sciences. A novel octanuclear nickel(II)-molybdenum(VI) heterometallic cluster based on the salicylhydroxamate ligand, namely di-μ3-acetato-di-μ2-acetato-di-μ3-hydroxido-di-μ3-oxido-tetraoxidooctakis(pyridine-κN)bis(μ5-salicylhydroxamato)hexanickel(II)dimolybdenum(VI) monohydrate, [Mo2Ni6(C7H4NO3)2(C2H3O2)4O5(OH)2(C5H5N)8]·H2O, (I), was synthesized by the reaction of sodium molybdate, nickel acetate and salicylhydroxamic acid in a dimethylformamide/pyridine/methanol solution at room temperature. The salicylhydroxamate(3-) (shi(3-)), acetate and oxide ligands adopt complicated coordination modes and link six Ni(II) and two Mo(VI) cations into the octanuclear heterometallic cluster. All of the metal cations exhibit octahedral coordination geometries and are connected to each other through the sharing of corners, edges or planes. The heterometallic clusters are further connected to form two-dimensional supramolecular layers through weak C-H...O hydrogen bonds. Studies of the magnetic properties of the title compound reveal antiferromagnetic interactions between the Ni(II) cations.

Secondary Sphere Hydrogen Bonding in Monocopper Complexes of Potentially Dinucleating Bis(carboxamide) Ligands.

Reaction of a macrocyclic ligand precursor comprising two bis(carboxamido)pyridine units (H4L4) connected by ethylene linkers with NMe4OH and CuX2 (X = Cl, OAc, or OTf) yielded monocopper complexes [NMe4][(H2L4)Cu(X)] (X = Cl (3), OAc (4), or OH (5)), in contrast to previous work using a related ligand with ortho-phenylene linkers wherein dicopper compounds were isolated. X-ray structures of the complexes revealed hydrogen bonding from the free carboxamide N-H groups in the doubly protonated form of the ligand (H2L4- ) to the monodentate fourth ligand coordinated to the Cu(II) ion. Similar secondary sphere hydrogen bonding interactions were identified in multinuclear compounds [NMe4]2[((H2L4)Cu)n(CO3)] (n = 2 or 3) that were isolated from exposure of 5 to air. Cyclic voltammetry revealed oxidations of 3 and 5 at potentials ~300 mV higher than analogous monocopper complexes of bis(arylcarboxamido)pyridine ligands which lack the intramolecular hydrogen bonds, consistent with removal of electron density from the metal center by the hydrogen bonding array. Another ligand variant (H4L5) with ortho-phenylene linkers and only one bis(carboxamido)pyridine moiety yielded monocopper complexes [NMe4][(H2L5)Cu(OAc)] • DMF (8) and [NMe4][(H2L5)CuCl)] • CH3CN (9), but the X-ray structures revealed a different hydrogen bonding arrangement to the solvate molecules. Nonetheless, a high redox potential for 9 was observed, consistent with intramolecular hydrogen bonding interactions in solution.

A heterotrimetallic Ir(iii), Au(iii) and Pt(ii) complex incorporating cyclometallating bi- and tridentate ligands: simultaneous emission from different luminescent metal centres leads to broad-band light emission

Di- and tri-nuclear metal complexes incorporating gold(III), iridium(III) and platinum(II) units linked via a 1,3,5-triethynylbenzene core are reported, together with the corresponding mononuclear complexes as models. The gold(III) and platinum(II) units comprise tridentate, cyclometallating, C^N^C and N^N^C-coordinating ligands, respectively, with the Ar-C≡C- directly bound to the metal at the fourth coordination site. The iridium moiety is an Ir(ppy)2(acac) unit bound to the triethynylbenzene through a phenyl substituent at the 3-position of the acac ligand. The multinuclear compounds are prepared, using a modular synthetic strategy, from the monometallic complexes. All of the compounds are luminescent in solution at room temperature, and their photophysical properties were studied. The triplet excited state energies of the mononuclear complexes lie in the order Au > Ir > Pt. Consistent with this order, energy transfer from Au to Ir and from Au to Pt is observed, leading to quenching of the Au emission in the gold-containing multinuclear complexes. Energy transfer from Ir to Pt occurs at a rate that only partially quenches the Ir-based emission. As a result, the dinuclear Ir-Pt and trinuclear Au-Ir-Pt complexes display broad emission across most of the visible region of the spectrum.

Building Hg(II)/Cu(I) multinuclear compounds from mercury bis(phenylselenolate)

In this article we present the syntheses and characterization of multinuclear compounds [HgCu2X2(SePh)2(PPh3)4] (1) (X=Cl(a), Br(b), I(c)) and [Hg6Cu4(SePh)16] (2) starting with the compound Hg(SePh)2. The reaction of Hg(SePh)2 with CuX (X=Cl, Br, I) derivatives results in the trinuclear complexes 1(a–c) and in the cluster complex 2. The compounds were characterized by single crystal X-ray diffractometry, elemental analysis, infrared and UV–vis spectroscopy. These results were correlated with data calculated by DFT – Density Functional Theory calculations.

ChemInform Abstract: Rational Creation of Chiral Multinuclear and Metallosupramolecular Compounds from Thiol‐Containing Amino Acids

AbstractReview: 166 refs.

β-Diketiminato 3d-metal compounds: Synthesis, characterization and catalytic behavior towards ethylene

The lithium β-diketiminate ( 1c, [Li{N(2,6- i Pr 2C 6H 3)C(Ph)CHC( t Bu)NH}] 2 represented as (Li L) 2) reacted with 3d-metal (II) chlorides to afford the corresponding compounds ( 2– 7). All metal compounds were fully characterized by elemental, spectroscopic analyses and the single-crystal X-ray diffraction. The coordination geometries around the metals are shown to be tetrahedral within the trinuclear Co 2Li compound ( 2), planar in M L 2 (M = Co, 3), pseudo-tetrahedral conformation in the M L 2 with M as Mn ( 4), Fe ( 5) or Zn ( 6), and square planar in the dinickel compound ( 7). Indicated by the trimetallic Co 2Li compound 2, a six-membered ring is constructed of three metal atoms and three bridged chlorides as a twisted conformation. An inversion center is present in the centroid of the Ni 2Cl 2 four-membered ring within compound 7. The plausible mechanism of forming M L 2 was proposed through the chloro-bridged multinuclear compounds on the basis of isolated intermediates of trinuclear ( 2) and dinuclearic ( 7) compounds. Upon treatment with methylaluminoxane (MAO), the nickel compound 7 possessed good activity towards ethylene oligomerization, whereas the other metal compounds showed moderate activities towards ethylene polymerization.

ChemInform Abstract: New Heterospin Complexes: The Multinuclear Compounds of Transition Metals with Nitroxyl Radicals

AbstractReview: 115 refs.

New heterospin complexes: The multinuclear compounds of transition metals with nitroxyl radicals

Synthesis and properties of the complex heterospin systems based on polynuclear transition metal compounds with stable nitroxides are reviewed. The appearance of the new synthetic approaches in the molecular magnetism area presents infinite possibilities in the chemical design of magnetically active

Novel Bis-platinum Complexes Endowed with an Improved Pharmacological Profile

Multinuclear platinum complexes are characterized by a peculiar DNA binding mode and higher cytotoxic potency than the mononuclear complexes, and efficacy against a wide range of preclinical tumor models. To reduce the high irreversible plasma protein binding and improve the chemical and metabolic drug stability, novel bis-platinum complexes were designed starting from the parent compound CT-3610. The novel second-generation bis-platinum complexes utilize alkylcarboxylate as leaving groups to improve their pharmacokinetic and pharmacodynamic profiles, thus overcoming the limitations of the previously developed multinuclear compounds. The selected compounds [CT-47518 and CT-47463, respectively (bis-capronate) platinum and (bis-butyrate) platinum], have similar in vitro degradation kinetics in human and murine plasma and, above all, an increased stability when compared to CT-3610, particularly in human plasma. In addition, both compounds exhibited a marked cytotoxic potency as compared with cisplatin and oxaliplatin. Interestingly, they were capable of overcoming resistance mediated by DNA mismatch repair defects in different cellular models. The complexes showed marked antitumor efficacy in Pt-refractory tumor xenografts, with remarkable activity in terms of tumor growth inhibition and tumor growth delay. The improved stability profile in human plasma compared to early bis- and triplatinum complexes together with the marked activity in cellular systems as well as in in vivo models, make CT-47518 and CT-47463 attractive candidates for further development.

Studies on activities, cell up take and DNA binding of four multinuclear complexes of the form: [{ trans-PtCl(NH 3) 2} 2μ-{ trans-Pd(NH 3) 2-(H 2N(CH 2) nNH 2) 2}]Cl 4 where n = 4–7

The activity against human cancer cell lines including ovarian: A2780, A2780 cisR, cell up take, DNA-binding and nature of interaction with pBR322 plasmid DNA have been studied for four multinuclear complexes code named DH4Cl, DH5Cl, DH6Cl and DH7Cl, having the general formula: [{ trans-PtCl(NH 3) 2} 2μ-{ trans-Pd(NH 3) 2-(H 2N(CH 2) n NH 2) 2}]Cl 4 where n = 4, 5, 6 and 7 for DH4Cl, DH5Cl, DH6Cl and DH7Cl, respectively. The compounds are found to exhibit significant anticancer activity against ovarian cancer cell lines: A2780, A2780 cisR and A2780 ZD0473R. DH6Cl in which the linking diamine has six carbon atoms is found to be the most active compound. As the number of carbon atoms in the linking diamine is decreased below six and increased above six, the activity is found to decrease, illustrating structure–activity relationship. All the multinuclear compounds are believed to form a plethora of long-range interstrand GG adducts with DNA dictated by the sequence of bases in the DNA strands. Increasing prevention of BamH1 digestion with the increase in concentration of the compounds is due to global changes in DNA conformation brought about by interstrand long-range binding of the compounds with DNA.

Tetranuclear Complexes Containing Bimetallic Tetracarboxylates and Ferrocene − Models for Subunits of One-Dimensional Organometallic Polymers

The tetranuclear compounds M2(O2C-R)4L2 [M = Rh, R = nC7H15, L = ferrocenyl-4-pyridylacetylene (FPA) (1a); M = Rh, R = CH3, L = FPA (1b); M = Mo, R = CF3, L = FPA (2b); M = Rh, R = nC7H15, L = 4-ferrocenylpyridine (FP) (3a); M = Rh, R = CH3, L = FP (3b); M = Mo, R = nC7H15, L = FP (4a); M = Mo, R = CF3, L = FP (4b)] have been synthesized by the reaction of bimetallic tetracarboxylates with L in a 1:2 ratio, in a noncoordinating solvent. The reaction of Mo2(O2C-nC7H15)4 with FPA in a 1:2 molar ratio leads to a trinuclear compound Mo2(O2C-nC7H15)4(FPA) (2a). A soluble oligomer [Rh2(O2C-nC7H15)4(BPEF)]n [5, BPEF = 1,1′-bis(4-pyridylethynyl)ferrocene] is obtained by the reaction of Rh2(O2CnC7H15)4 with BPEF in a 1:1 ratio in CH2Cl2 or CHCl3, whereas the reaction of Mo2(O2C-nC7H15)4 with BPEF leads to a pentanuclear compound [Mo2(O2C-nC7H15)4]2(BPEF) (6), even when BPEF is in excess. 1H NMR, Raman, UV/Vis absorption spectroscopy and cyclic voltammetry indicate that the metal-metal bonds are weakened by the metal-axial ligand interaction and the donor-acceptor interactions occurring between the building blocks of the multinuclear compounds and oligomers. The interaction between the bimetallic centers and the ferrocene moiety is enhanced by shortening the distances between them. This shortening is achieved by modification of the axial ligand from FPA to FP. A significant electronic communication between the ferrocene units is not observed.

Electrospray and Collision-induced Dissociation Mass Analysis of Star-burst Type Tetranuclear Complexes

A number of star-burst type tetranuclear complexes denoted by [Met(II)L2B]3RuX8 (Met = Ru, Os) were examined by positive electrospray (ES) mass spectrometry, where L is bpy (2,2′-bipyridine) or btfmb (4,4′-bis(trifluoromethyl)-2,2′-bipyridine), bridging ligand B is 1,1′-dimethyl-2,2′-bis(2″-pyridyl)-6,6′-bibenzimidazole (dmbpbim), 2,2′-bis(benzimidazol-2-yl)-4,4′-bipyridine (bbbpyH2) or the related ligand, and X is ClO4-. Multiply charged ions with the charge state from 8+ to 3+ were observed in the full- scan ES mass spectra. Different charged ions were generated by the combination of counterion loss and protonation/deprotonation of the bridging ligand B. Collision-induced dissociation (CID) of the multiply charged ion made it clear that loss of one or more HX neutral is a major process for lower charge states, whereas complete fragmentation takes place for higher charge states and the fragments are based on a subunit group of [Met(II)L2B]2+. Insertion of formal O2- produced from ClO4- counterion was observed for the complexes without active protons even if low-energy CID experiments, but not for the complexes with active protons. Advantages of ES mass spectrometry are demonstrated for these multinuclear compounds and the CID chemistry of the ions investigated is discussed.

Lineare Oligophosphaalkane, XXIV Synthese und strukturelle Charakterisierung von Cu8‐Mehrkernkomplexen mit Elektronenmangel‐Phosphidobrücken

Linear Oligophosphaalkanes, XXIV. – Syntheses and Structural Characterisation of Cu8 Complexes with Electron‐Deficient Phosphido BridgesReaction of silylphosphanes (Me3Si)RP–CH2–PR(SiMe3) (R = iPr, tBu, 2,4,6,‐Me3C6H2) with four equivalents of copper(1) halides CuX (X = Cl, Br) or a mixture of two equivalents of CuCl and Cul in the presence of pyridine as an auxiliary ligand affords octanuclear copper(1) complexes of composition Cu8X4(RP–CH2–PR)2(Py)n(CH3CN)m (n = 5, m = 0; n = 4, m = 1; X = Cl, Br, I). Multinuclear compounds of this type may also be obtained by deprotonation of the disecondary phosphanes HRP–CH2–PRH (R = iPr, Ph, 2,4,6‐Me3C6H2) with strong organic bases (DBU) in the presence of CuCl and pyridine. The X‐ray structural analysis of Cu8Cl4(iPr–P–CH2–PiPr)2(Py)5 (3a) (space group P21/c) reveals a Cu4(P–C–P)2 skeleton to which four CuCl(Py)n units (n = 1, 2) are coordinated by Cu–Cl and Cu–P bridges. The phosphorus atoms of the electron‐deficient μ3–PRR′ bridges formed thereby show a distorted trigonal bipyramidal coordination with almost planar PCu3 units. Due to the multiple bridging of the Cu(I) ions in 3a the Cu ⃛Cu distances in the Cu8 complex are relatively short (247.1–276.5 pm).

Antiplasticizing effect of hydroxyaromatic compounds on the mechanical properties of polycaproamide

Modification of polycaproamide by multinuclear hydroxyaromatic compounds of the tanning agent class of synthetic and natural origin is an effective method of enhancing its mechanical properties. The elasticity modulus and the forced elasticity limit of isotropic films in the air-dry state at 20°C after modification rise 2.5–4 and 2–3 times respectively. Increase in these parameters and passage from plastic to brittle fracture allow the observed phenomenon to be classed as antiplasticization.

Chelated I(V) Alcoholate Fluorides

The behavior of IF 5 towards nucleophilic exchange of fluoride against mono and polyfunctional alcoholates in aprotic media was investigated using silylated alcohols as educts. In a series of homologous bifunctional alcoholates −O(CH 2) nO − (n = 2,3,4,5,6,12) systems with short CH 2-chains (n < 4) form short lived species IF 4[O(CH 2) nO]X (X = SiMe 3, IF 4) which rearrange to mononuclear chelates IF 3[O(CH 2) nO] of high stability. Dialcoholates with long CH 2-chains (n > 4) behave as bridging ligands forming multinuclear compounds IF 4[O(CH 2) nO]IF 4 and IF 3[O(CH 2) nO] m (m ≥ 2). In a series of α - and β-ethandiolates with increasing number of CH 3- groups in α - and β-positions short lived intermediates and stable chelates IF 3 [OC 2H 4−n(CH 3) nO] and IF[OC 2H 4−n(CH 3) nO] 2 (n = 0−4) are observed and characterized. Time and temperature dependence of 19F-NMR-spectra in relation to degree of methylation, arrangement and stereo-chemistry are discussed. Reactions of IF 5 with a geminal dialcoholate CCl 3CH(O −) 2 and a trifunctional alcoholate CH 3C(CH 2O −) 3 are reported.

Beiträge zur chemie des iodpentafluorids teil II. Iod(V)-verbindungen mit α,ω-difunktionellen alkoholaten

Nucleophilic substitution reactions of iodine pentaflurode with a series of homologous bifunctional alcoholates −O(CH 2) nO − (n=2,3,4,5,6,12), a geminal dialcoholate CCℓ 3 CH(O −) 2 and a trifunctional alcoholate CH 3C(CH 2O −) 3 protected by (CH 3) 3Si - groups are reported. Systems with short CH 2 - chains (n<4) first form short lived species IF 4[O(CH 2) nO]X (X = SiMe 3, IF 4) which rearrange to mononuclear chelates IF 3[O(CH 2) nO] of high stability. Dialcoholates with long CH 2-chains (n>4) behave as bridging ligands forming stable multinuclear compounds IF 4[O(CH 2) nO]IF 4 and {IF 3[O(CH 2) nO]} m (m≥2). 1,4-Butanediolate is on the border line of the two systems. Products with greater substitution IF[O(CH 2) nO] 2 (n=2,3) and IF 2(OCH 2) 3CCH 3 are also characterized. The dependence of 19F-NMR-shifts on the nature and arrangement of ligands is discussed.