Heterometallic Complexes Research Articles

Heterometallic Chain Compounds of Tetrakis(µ-carboxylato)diruthenium and Tetracyanidoaurate

Heterometallic complexes of tetrakis(µ-carboxylato)diruthenium(II,III) with tetracyanidoaurate(III) [Ru2(RCOO)4Au(CN)4]n (R = CH3 (1), C2H5 (2), i-C3H7 (3), and t-C4H9 (4)) were synthesized and characterized by C,H,N-elemental analysis and infrared spectroscopy and diffuse reflectance spectroscopy. The molecular structures were determined by a single-crystal X-ray diffraction method. A polymeric arrangement with the Ru2(RCOO)4+ units alternately linked by Au(CN)4− units is formed in these complexes. The trans-bridging mode of the Au(CN)4− unit for connecting the two Ru2(RCOO)4+ units was observed for 1 and 4, while the cis-bridging mode of the Au(CN)4− unit was observed for 2 and 3. Magnetic susceptibility data with variable temperature were modeled with a zero-field splitting model (D = 75 cm−1) and the presence of weak antiferromagnetic coupling between the RuIIRuIII units (zJ = −0.15~−0.10 cm−1) was estimated. N2-adsorption isotherms showed Type II curves with SBET of 0.728–2.91 m2 g−1.

Phosphorescent Host-Guest Complexes on the Basis of Polyhedral Oligomeric Silsesquioxane-Functionalized Metallotweezers.

Phosphorescent host-guest systems have attracted considerable attention because of their intriguing properties and diverse applications. In this study, a polyhedral oligomeric silsesquioxane-functionalized gold(III) tweezer receptor has been designed and synthesized. It is capable of sandwiching platinum(II) terpyridine compounds into its cavity with a high noncovalent binding affinity (association constants: ∼105 M-1 in chloroform). The resulting heterometallic host-guest complexes exhibit enhanced phosphorescent emission compared with those of the individual species in chloroform, thanks to the prevention of vibration and rotation upon noncovalent complexation. They can further assemble into nanospheres in chloroform/diethyl ether (1:9, v/v) owing to phase segregation between the metallotweezer/guest motif and the peripheral polyhedral oligomeric silsesquioxane unit. When terpyridine platinum(II) chloride serves as the complementary guest, the resulting noncovalent system displays an intraligand emission at the individual host-guest complexed state yet excimeric emission at the supramolecular assembled state, yielding the phosphorescent solvatochromic behaviors. Overall, the polyhedral oligomeric silsesquioxane-functionalized metallotweezer combines guest encapsulation and supramolecular assembly capabilities, which provides new avenues for color-tunable phosphorescent materials.

Trinuclear cyanido-bridged MII-WV complexes (M = Mn, Co): Crystal structures and magnetic properties

Two new trinuclear heterometallic complexes, [{MnII(L)(CH3OH)}2{WV(CN)8}](NO3)·CH3OH·H2O (2) and [{CoII(L)(CH3OH)}2{WV(CN)8}](NO3)·CH3OH·H2O (3), have been assembled from mononuclear cationic modules, [M(L)(H2O)2]2+, and [W(CN)8]3– as a metalloligand (M = MnII; CoII, L is the pentadentate ligand resulting from the condensation reaction between 2,6-diacetylpyridine and semicarbazide). The crystal structure of the manganese(II) precursor, [MnII(L)(H2O)2](NO3)2·H2O 1, and of the trinuclear compounds 2 and 3 have been solved. Within the three compounds the 3d metal ions show a pentagonal bipyramidal coordination geometry. The magnetic properties of compounds 2 and 3 have been investigated. Compound 2 shows an irregular spin state structure with S = 9/2 arising from MnII-WV antiferromagnetic interactions (J = −8.00 cm−1, H = -2JS1S2). In compound 3, the CoII-WV exchange interaction was found ferromagnetic (J = +12.3 cm−1).

A Bis-(carbone) Pincer Ligand and Its Coordinative Behavior toward Multi-Metallic Configurations.

Carbones are divalent carbon(0) species that contain two lone pairs of electrons. Herein, we have prepared the first known stable and isolable free bis-(carbone) pincer framework with a well-defined solid-state structure. This bis-(carbone) ligand is an effective scaffold for forming monometallic (Ni and Pd) and trinuclear heterometallic complexes with Au-Pd-Au, Au-Ni-Au, and Cu-Ni-Cu configurations. Sophisticated quantum-theoretical analyses found that the metal-metal interactions are too weak to play a significant role in upholding these multi-metallic configurations; rather, the four lone pairs of electrons within the bis-(carbone) framework are the main contributors to the stability of the complexes.

A Bis‐(carbone) Pincer Ligand and Its Coordinative Behavior toward Multi‐Metallic Configurations

AbstractCarbones are divalent carbon(0) species that contain two lone pairs of electrons. Herein, we have prepared the first known stable and isolable free bis‐(carbone) pincer framework with a well‐defined solid‐state structure. This bis‐(carbone) ligand is an effective scaffold for forming monometallic (Ni and Pd) and trinuclear heterometallic complexes with Au−Pd−Au, Au−Ni−Au, and Cu−Ni−Cu configurations. Sophisticated quantum‐theoretical analyses found that the metal–metal interactions are too weak to play a significant role in upholding these multi‐metallic configurations; rather, the four lone pairs of electrons within the bis‐(carbone) framework are the main contributors to the stability of the complexes.

SYNTHESIS, SPECTRAL CHARACTERIZATION AND STABILITY OF THE NEW ND (III) AND CO (II) HETEROMETALLIC COMPLEXES WITH AMINOPOLYCARBOXYLIC ACIDS

New heterometallic complexes of Nd(III) and Co(II) based on ethylenediaminetetraacetic and ethylenediaminedisuccinic acids have been synthesized. The complexes studied by electron absorption spectroscopy, IR-spectroscopy, and thermogravimetric analysis. The influence of a number of factors on the properties and structure of heteronuclear complexes is discussed. The spectral characteristics of homonuclear and heteronuclear complexes are compared. A theoretical analysis of the geometry of Co(II) and Nd(III) complexes with ethylenediaminesuccinic acid was carried out by the semi-empirical PM7 method. It has been shown that the f-d-complexes are of the folded type, in which the ligand-complexone realizes the maximum denticity to Nd(III), and the Co(II) coordination sphere is formed by bridging edta/edds carboxyl groups and intrasphere water molecules. The Co(II) coordination polyhedron corresponds to a distorted octahedron, and the Nd(III) coordination polyhedron corresponds to a one-capped square antiprism (C4v) with the coordination number Nd(III)=8. During study fixed that heterometallic complexes have the same structure in solutions and in the solid state.

The incorporation of upper vs lower rim substituted thia- and calix[4]arene ligands into polydiacethylene polymeric bilayers for rational design of sensors to heavy metal ions

1,3-Diketone calix [4]arene (CA) and thiacalix [4]arene (TCA), with the hydrophobic substituents introduced onto lower or upper rims respectively, form mixed aggregates with 10,12-pentacosadiynoic acid (PCDA) through the thin film hydration technique. Computer simulations, showing the arrangement of TCA and CA molecules in supramolecular clusters with PCDA molecules, suggest that PCDA assemblies with both cyclophanes are a convinient basis for the coordination of metal ions. However, photopolymerization of mixed aggregates reveals more disruption of the vesicular nanostructure of polydiacetylene (PDA) when CA molecules are included compared to TCA. The incorporation of the TCA and CA ligands influences the ability of the mixed PDA-bilayers to conformational and spectral changes and provides tight coordination of Tb3+ ions and efficient sensitizing of the Tb3+-centered luminescence. The PDA-bilayers incorporated by terbium TCA complex provide more sensitive response on the series of heavy metal ions vs their CA-based analogues. The surface exposed TCA rims and carboxylate moieties of PDA provide two different binding sites for Tb3+ and heavy metal ions. Both distribution of Tb3+ and heavy metal ions between these sites and heterometallic complex formation are revealed as the factors affecting the luminescence response of PDA-TCA terbium complex in the solutions of heavy metal ions. The interplay between these factors is the reason for the different luminescence response of PDA-TCA terbium complex on Cd2+, Hg2+ and Pb2+ ions. The PDA-vesicles incorporated by terbium TCA complex exhibit easier phase separation vs the PDA vesicles themselves, which favors the extraction of Pb2+ ions.

Novel heterometallic Zn(II)-L-Cu(II) complexes: studies of the nucleophilic substitution reactions, antimicrobial, redox and cytotoxic activity

New heterometallic complexes [{ZnCl(terpy)(μ-pyrazine)CuCl(terpy)}] (ClO4)2 (Zn-L1-Cu) and [{ZnCl(terpy)(μ-4,4′-bipyridyl)CuCl(terpy)}] (ClO4)2 (Zn-L2-Cu) (where terpy = 2,2′:6′,2′′-terpyridine, L1 = pyrazine, L2 = 4,4′-bipyridyl) were synthesized. The substitution reactions with biologically important nucleophiles were investigated at pH 7.4 by UV-Vis spectrophotometric method. The obtained results have shown different orders of reactivity of guanosine-5′-monophosphate (5′-GMP), inosine-5′-monophosphate (5′-IMP) and glutathione (GSH) toward heterometallic Zn(II)-L-Cu(II) complexes. Spectrophotometric titration of diaqua Zn-L-Cu complexes has shown that aqua ligands coordinated to both metal centers can exhibit different pK a values depending on the distance between them. Both synthesized complexes showed moderate antimicrobial activity against most of the tested bacterial and fungal strains. The cytotoxic activity of heteronuclear Zn-L1-Cu and Zn-L2-Cu complexes was determined on human colorectal cancer (HCT-116) and human healthy lung pleura (MRC-5) cell lines. Both complexes exerted significant cytotoxic effects, especially after 72 h (IC50 < 0.01 µM) and significantly reduced cell viability. Complexes induced a significant increase in reactive radical species which consequently induced cell death and thus lower IC50 values. As the response of the cells to an increased radical level induced by treatment, glutathione level also increased in a time and dose-dependent manner.

Applications of Low-Valent Transition Metalates: Development of a Reactive Noncarbonyl Rhenium(I) Anion.

Low-valent transition metalates─anionic, electronic-rich organometallic complexes─comprise a class of highly reactive chemical reagents that find integral applications in organic synthesis, small-molecule activation, transient species stabilization, and M-E bond formation, among others. The inherent reactivity of such electron-rich metal centers has necessitated the widespread use of strong backbonding ligands, particularly carbonyls, to aid in the isolation and handling of metalate reagents, albeit sometimes at the expense of partially masking their full reactivity. However, recent synthetic explorations into transition-metalate complexes devoid of archetypic back-bonding ligands have led to the discovery of highly reactive metalates capable of performing a variety of novel chemical transformations.Building on our group's long-standing interest in reactive organometallic species, a series of rational progressions in early-to-middle transition-metal chemistry ultimately led to our isolation of a rhenium(I) β-diketiminate cyclopentadienide metalate that displays exceptional reactivity. We have found this Re(I) metalate to be capable of small-molecule activation; notably, the complex reversibly binds dinitrogen in solution and can be utilized to trap N2 for the synthesis of functionalized diazenido species. By employing isolobal analogues to N2 (CO and RNC), we were able to thoroughly monitor the mechanism of activation and conclude that the metalate's sodium counterion plays an integral role in promoting dinitrogen activation through a novel side-on interaction. The Re(I) metalate is also used in forming a variety of M-E bonds, including a series of uncommon rhenium-tetrylene (Si, Ge, and Sn) complexes that display varying degrees of multiple bonding. These metal tetrylenes act to highlight deviations in chemical properties within the group 14 elements. Our metalate's utility also applies to metal-metal bond formation, as demonstrated through the synthesis of a heterotetrametallic rhenium-zinc dimer. In this reaction, the Re(I) metalate performs a dual role as a reductant and metalloligand to stabilize a transient Zn22+ core fragment. Finally, the metalate displays unique reactivity with uranium(III) to yield the first transition metal-actinide inverse-sandwich bonds, in this case with three rhenium fragments bound through their Cp moieties surrounding the uranium center. Notably, throughout these endeavors we demonstrate that the metalate displays reactivity at multiple locations, including directly at the rhenium metal center, at a Cp carbon, through a Cp-sandwich mode, or through reversibly bound dinitrogen.Overall, the rhenium(I) metalate described herein demonstrates utility in diverse applications: small-molecule activation, the stabilization of reduced and/or unstable species, and the formation of unconventional M-E/M-M bonds or heterometallic complexes. Moving forward, we suggest that the continued discovery of noncarbonyl, electron-rich transition-metal anions featuring new or unconventional ligands should produce additional reactive organometallic species capable of stabilizing unique structural motifs and performing novel and unusual chemical transformations.

Insight into the Gd–Pt Bond: Slow Magnetic Relaxation of a Heterometallic Gd–Pt Complex

Abstract Lanthanide (Ln) compounds are common research targets in the field of magnetism and optics. Their properties arise from the electrons localized in the f-orbital. Moreover, the effect of the covalency between lanthanide and ligands on magnetism has attracted significant attention. We have provided insight into the Gd–Pt bond (of the heterometallic Ln-Pt complexes: {[Pt(PhSAc)4]Ln[(PhSAc)4Pt]} NEt4·2DMF (Ln = Y(0), La(1), Gd(2); PhSAc = thiobenzoate, NEt4 = tetraethylammonium)); single-crystal polarized X-ray absorption near edge structure (XANES) reveal the electronic states around metal ion, where spectra of Gd-LIII edges show the Gd–Pt direction has the highest covalency (less ionic) around Gd ion in 2. In addition, calculating natural bonding (NBO) analysis, natural population analysis (NPA), LOL, and atoms in molecules (AIM), ab initio calculations reveal the role of metallic and organic ligands in the electronic and magnetic properties of Ln complexes. The slow magnetization relaxation of the Gd complex, which has not been reported previously in the Pt–Gd–Pt system, was observed up to 45 K, the highest temperature reported to date among isolated Gd-complexes (frequency range: 0.1–10000 Hz).

Contrasting Networks and Entanglements in Uranyl Ion Complexes with Adipic and trans,trans-Muconic Acids.

Adipic (hexane-1,6-dicarboxylic, adpH2) and trans,trans-muconic (trans,trans-hexa-2,4-diene-1,6-dicarboxylic, mucH2) acids have been reacted with uranyl cations under solvo-hydrothermal conditions, yielding nine homo- or heterometallic complexes displaying in their crystal structure the effects of the different flexibility of the ligands. The complexes [PPh4]2[(UO2)2(adp)3] (1) and [Ni(bipy)3][(UO2)2(muc)3]·5H2O (2), where bipy is 2,2'-bipyridine, crystallize as diperiodic networks with the hcb topology, the layers being strongly puckered or quasiplanar, respectively. Whereas [(UO2)2(adp)3Ni(cyclam)]·2H2O (3), where cyclam is 1,4,8,11-tetraazacyclotetradecane, crystallizes as a diperiodic network, [(UO2)2(muc)3Ni(cyclam)]·2H2O (4) is a triperiodic framework in which the NiII cations are introduced as pillars within a uranyl-muc2- framework with the mog topology. [UO2(adp)(HCOO)2Cu(R,S-Me6cyclam)]·2H2O (5), where R,S-Me6cyclam is 7(R),14(S)-5,5,7,12,12,14-hexamethylcyclam, is a diperiodic assembly with the sql topology, and it crystallizes together with [H2NMe2]2[(UO2)2(adp)3] (6), a highly corrugated hcb network with a square-wave profile, which displays 3-fold parallel interpenetration. In contrast, [(UO2)3(muc)2(O)2Cu(R,S-Me6cyclam)] (7) is a diperiodic assembly containing hexanuclear, μ3-oxido-bridged secondary building units which are the nodes of a network with the hxl topology. The two related complexes [PPh3Me]2[(UO2)2(adp)3]·4H2O (8) and [PPh3Me]2[(UO2)2(muc)3]·H2O (9) crystallize as hcb networks, but their different shapes, undulated or quasiplanar, respectively, result in different entanglements, 2-fold parallel interpenetration in 8 and 2-fold inclined 2D → 3D polycatenation in 9.

Construction of two new photoluminescent 3D heterometallic complexes and their nursing application values on ICU infection

Construction of two new photoluminescent 3D heterometallic complexes and their nursing application values on ICU infection

A hexanuclear discrete assembly and a two dimensional coordination polymer constructed from heterotrinuclear [(CuL)2Zn]2+ nodes and dicyanamide spacer (H2L = salen type Schiff base ligands)

Two new Cu(II)–Zn(II) complexes as a discrete hexanuclear cluster [{(CuL1)2Zn}2(μ1,5-N(CN)2)2](ClO4)2(1) and a two dimensional (2D) coordination polymer [(CuL2)2Zn(μ1,5-N(CN)2)2]n (2) have been isolated by mixing two similar tetradentate Schiff bases H2L1 (N,N′-bis(ɑ-ethylsalicylidene)-1,3-propanediamine) and H2L2 (N,N′-bis(salicylidene)-1,3-pentanediamine) separately with Cu(ClO4)2·6H2O, Zn(ClO4)2·6H2O and NaN(CN)2 ​at same reaction condition. The heterometallic complexes have been structurally characterized by single crystal X-ray analyses showing that both are formed by angular trinuclear nodes and μ1,5-dicyanamide spacers. The trinuclear nodes ([(CuL1)2Zn]2+ in 1 and [(CuL2)2Zn]2+ in 2 are produced in situ from their corresponding reactants. The two Schiff base ligands coordinating the Cu(II) ions through the N2O2 donor set are additionally bonded to a Zn(II) ion with the four phenoxido oxygen atoms that act as bridging atoms. The zinc ion completes its coordination geometry with two terminal nitrogen atoms of two different dicyanamide spacers. The orientation of spacers from zinc ion are convergent in 1 whereas divergent in 2. Thus, two [(CuL1)2Zn]2+ nodes are interconnected by double μ1,5-dicyanamide bridges via Zn(II) centres to form discrete hexanuclear assembly of complex 1. On the other hand, [(CuL2)2Zn]2+ nodes in 2 are joined by μl,5-dicyanamide that bridge Zn(II) to Cu(II) centres of symmetry related units in order to construct a 2D coordination polymer. Consequently, the final coordination environment around Zn(II) is octahedral in both complexes whereas that around Cu(II) are square planar and square pyramidal in 1 and 2 respectively.

Photo-generation of H2 by heterometallic complexes.

Multiple and different metals in a complex can accomplish single and sequential multi-step reactions, providing valuable procedures to obtain chemicals in one-pot synthetic routes. Biology has shown how cooperative catalysis is a powerful method for the synthesis of complicated molecules. One of the most attractive targets for current chemists is the synthesis of H2 by a simple and economical procedure, mainly if it is produced from water using visible light as the energy source. This review aims to show how heterometallic complexes have been recently used to catalyze the photochemical production of H2.

Platinum-containing heterometallic complexes in cancer therapy: advances and perspectives

This review focuses on Pt–M heterometallic complexes (M = Ru, Au, Ti, Fe, Rh, Pd, Cu, Ir, Gd, Eu, Re and Tc) for cancer therapy. The design, anticancer activities, mechanism of action, and interplay between different metal center(s) are discussed.

Synthesis and thermal properties of the heterometallic nickel–ruthenium complex: a potential precursor for catalytically active nanosized Ni–Ru alloy

Thermal decomposition of the novel heterometallic complex [RuNO(NO2)4OHNi(En)2] results in a single-phase metastable solid solution Ni0.5Ru0.5. The catalytic activity of the prepared nanoalloy in the CO methanation reaction was demonstrated.

A spectroscopic, structural, and computational study of Ag-oxo interactions in Ag+/UO22+ complexes.

Twelve novel Ag+/UO22+ heterometallic complexes have been prepared and characterized via structural, spectroscopic, and computational methods to probe the effects of Ag-oxo interactions on bonding and photophysical properties of the uranyl cation. Structural characterization reveals Ag-oxo interaction distances ranging from 2.475(3) Å to 4.287(4) Å. These interactions were probed using luminescence and Raman spectroscopy which displayed little effect on the luminescence intensity and the energy of the Raman active UO symmetric stretch peak as compared to previously reported Pb-oxo interactions. Computational efforts via density functional theory-based natural bond orbital analysis revealed that the highest stabilization energy associated with the Ag-oxo interaction had a value of only 11.03 kcal mol-1 and that all other energy values fell at 7.05 kcal mol-1 or below indicating weaker interactions relative to those previously reported for Pb2+/UO22+ heterometallic compounds. In contrast, quantum theory of atoms in molecules analysis of bond critical point electron density values indicated higher electron density in Ag-oxo interactions as compared to Pb-oxo interactions which suggests more covalent character with the Ag+. Overall, this data indicates that Ag+ has a less significant effect on UO22+ bonding and photophysical properties as compared to other Pb2+, likely due to the high polarizability of the cation.

Luminescence thermometry and field induced slow magnetic relaxation based on a near infrared emissive heterometallic complex.

The 1 : 1 : 1 reaction of YbCl3·6H2O, K3[Co(CN)6] and bpyO2 in H2O has provided access to a complex with formula [YbCo(CN)6(bpyO2)2(H2O)3]·4H2O (1) in a very good yield while its structure has been determined by single-crystal X-ray crystallography and characterised based on elemental analyses and IR spectra. Magnetic susceptibility studies showed the complex to be a field induced single molecule magnet, as confirmed by μ-SQUID measurements. CASSCF calculations confirm the existence of a mJ = 7/2 ground state, with rather large transverse components, responsible for the fast relaxation characteristic of compound 1 at zero DC field, which is reduced upon application of DC fields. Moreover, a combination of luminescence studies along with CASSCF calculation allows the identification of the band structure of the complex, which is ultimately related to its electronic properties. Compound 1 operates as a luminescent thermometer in the 125-300 K range with a maximum relative thermal sensitivity of ≈0.1% K-1 at 180 K.

Salt additives as activity boosters: a simple strategy to access heterometallic cooperativity in lactide polymerisation

Inorganic salt additives can activate carbonyl groups towards organic addition reactions. Here, we translate this concept to ring-opening polymerisation for the first time, generating heterometallic ProPhenol catalysts in situ, which show similar activity enhancements to pre-formed heterometallic complexes. Extremely high activities are observed, with K/Mg and K/Ca combinations converting >85 eq. lactide in 5 s at room temperature.

Single molecule magnet behavior and luminescence of {Ln4} and {LnZn} complexes

A series of tetranuclear coordination clusters [Ln4L2(HL)2(μ3-OH)2(NO3)2](NO3)2 [Ln = Dy (1·3CH3CN·5H2O), Gd (2·4CH3CN·5H2O), H2L = 6,6'-dimethoxy-2,2'-[2,2-dimethylpropane-1,3-diylbis-(nitrilomethylidyne)] diphenol] and dinuclear complexes [LnZnL(NO3)3(H2O)]·2CH3CN [Ln = Dy (3), Er (4), Yb (5), Lu (6)] were prepared and characterized. Static magnetic measurements revealed the presence of ferromagnetic interactions between the Dy(III) ions and weak antiferromagnetic couplings between the Gd(III) ions in 1 and 2. Dynamic magnetic studies showed that complexes 1 and 3 exhibit slow magnetic relaxation under a zero static field as expected for single molecule magnet (SMM) behavior, whereas complex 4 is a field-induced SMM. Clear hysteresis loops were observed for 1 and 3 at 2 K, verifying their SMM behavior. Luminescence investigations demonstrated that complexes 1 and 2 show ligand-based emission and can act as luminescence thermometers below 100 K, whereas complexes 3 and 5 display the characteristic emission of lanthanide ions. From the high-resolution emission spectra of 3 and 5, the energy gaps between the ground state and excited states of Dy(III) and Yb(III) ions were determined.