Heteronuclear Complexes Research Articles

Synthesis, characterization and catalytic studies of bimetallic heteronuclear complexes for the reduction of nitroaromatic compounds

Four mixed-ligand complexes were prepared and formulated as [Ln(H2OBA)(H2PZDC)] and [Ln(H2OBA)(H2PDC)] {Ln = La & Gd; H2OBA = 4,4-oxybisbenzoic acid; H2PDC = 2,3-pyridinedicarboxylic acid; H2PZDC = 2,3-pyrazinedicarboxylic acid}. The complexes were modified by a nickel/cobalt impregnation method to generate bimetallic complexes 1–8. Fourier transform infrared (FTIR) spectroscopy analysis of the bimetallic complexes indicated that the carboxylate coordinated to the lanthanide ion via the OH- group while the Ni2+ and Co2+ ions were preferentially bonded to the nitrogen donor ligand via the N- group. Complete catalytic reduction of 4-nitrophenol to 4-aminophenol by the Ni@ complexes gave a maximum reduction time of 37 minutes for complex 1 while complex 7 gave a reduction time of 21 minutes. The rate constants were observed to increase with an increase in temperature up to 50 °C for complexes 3, 5, and 7.

Synthesis, Crystal Structures and NMR Characterization of Molecular Silver Tin Chalcogenide Complexes

AbstractA series of heteronuclear silver tin chalcogenide complexes has been synthesized by reaction of phosphine coordinated silver acetate and diorganotin acetate with bis(trimethylsilyl)chalcogenide. In addition to the silver complexes with the general formula [(iPr3PAg)2(SnR2)E2]2 (1–6, R=Me, Ph, tBu and E=S, Se), [(iPr3PAg)3(SnPh2)(SnPh)S4] (7) and [(iPr3PAg)(SnPh2)(SnPh)Se2]2 (8) were obtained by exchange of phenyl groups in solution and redox processes, respectively. In addition to single crystal X‐ray structure analyses, NMR spectra involving the nuclei 1H, 31P, 77Se, 117/119Sn and 107/109Ag allowed a structural analysis of these complexes in solution. Each element present in complexes 5–8 consists of at least one isotope with nuclear spin I=1/2. In co‐thermolysis experiments of these complexes together with Zn(SC2H4S) or Zn(SeC2H4Se) as zinc sources binary and ternary chalcogenides as well as elemental silver are found.

Single crystal structure features of a new synthesized heteronuclear Mn/Cu complex, a precursor for heterogeneous catalytic conversion of CO

A unique hetero-nuclear complex formulated as [Cu(pydc)2Mn(H2O)5].2H2O (1) where pydc2− = pyridine-2,6-dicarboxylato has been synthesized through a facile and environment-friendly ultrasonic reaction. Complex 1 was characterized by various techniques, including single-crystal X-ray diffraction (SC-XRD). X-ray crystallographic analysis reveals that the parallelepiped green crystals of complex 1 have a monoclinic structure with space group P21/c. The CuII and MnII centers have distorted square bipyramid geometry, while extensive H-bonding interactions help to produce a three-dimensional network. The bimetallic Cu-Mn/Al2O3 catalyst was prepared by thermal decomposition of [Cu(pydc)2Mn(H2O)5].2H2O/Al2O3. Also, a reference catalyst formulated as Cu-Mn/Al2O3 was prepared via the impregnation conventional method. Characterization of catalysts was carried out using inductively coupled plasma mass spectrometry (ICP-MS), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) surface area. The performance of the catalysts was evaluated for CO conversion in the low-temperature water-gas shift (LT-WGS) reaction in the temperature range of 160–240 °C. A comparison of the WGS performance of these catalysts points out the potential application of inorganic complex in LT-WGS reaction. The catalyst constructed by thermal decomposition of complex 1 shows higher activity than the reference catalyst prepared by the impregnation conventional method.

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.

Ab initio Morse/long-range potential energy functions plus spectroscopic and thermophysical properties of heteronuclear diatomic complexes of xenon with the rare gases

New interatomic potential energy curves of xenon-helium (Xe-He), xenon-neon (Xe-Ne), and xenon-argon (Xe-Ar) atom pairs are developed by state-of-the-art ab initio calculations. Coupled cluster theory with single, double, and perturbative triple excitations [CCSD(T)] is used to calculate the majority of the interaction between atoms, on (multiple) augmented correlation-consistent basis sets for valence orbitals, extrapolated to the complete basis set (CBS) limit. Contributions from inner nuclear electronic correlation, relativistic effects, and higher-order excitations beyond CCSD(T) are also considered as corrections. For each system, an analytical Morse/long-range (MLR) potential functions, is fitted to 32 ab initio data using only 13 parameters: the poorest-quality fit yielded a dimensionless-root-mean-square-deviation (dd¯) of only 1.51. The ro-vibrational energy levels and wave functions, resonance states, effective radial potential energy curves, absorption spectra and thermophysical properties have also been computed.

SYNTHESIS, CRYSTAL STRUCTURES AND MAGNETIC PROPERTIES OF COORDINATION COMPOUNDS WITH NITRONYL NITROXIDE RADICALS AND [M(HFAC)2] (M = CUII AND MNII)

The reaction of metal hexafluoroacetylacetonato [MII(hfac)2, M = Cu, Mn] with the stable nitronyl nitroxide 2−(3−isobutyl−pyrazole)−4,4,5,5−tetramethylimidazoline−1−oxyl−3−oxide (L), resulted in one dimensional zig−zag chain systems [{Cu(hfac)2}2L2]n and [CuMn(hfac)4L2]n. The main feature inherent in the nature of [{Cu(hfac)2}2L2]n single crystals is their ability to undergo reversible structural rearrangements with temperature variation, accompanied by anomalies of magnetism. The value of cmT shown strongly antiferromagnetic at low temperature and becomes ferromagnetic when the temperature increases. And the heteronuclear complex [CuMn(hfac)4L2]n shows antiferromagnetic interactions between manganese and nitronyl nitroxide.

Synthesis and Characterisation of New {Fe2CrO} Heterotrinuclear Iron-chromium Clusters

Two new μ3-oxo trinuclear heterometallic Fe2IIICrIII complexes with furan-2-carboxylic and salicylic acids with the composition: [Fe2CrO(C4H3OCOO)6(CH3OH)3]NO3·0.5CH3OH and [Fe2CrO(C6H4(OH)COO)7(CH3OH)2]·2DMA were synthesized starting from iron(III) and chromium(III) salts mixture. The complexes structures were confirmed by elemental analysis, IR, Mössbauer spectroscopies, and X-ray analysis. The atomic absorption spectroscopy confirmed that the iron: chromium ratio is 2:1. The thermal properties of both heteronuclear complexes have been investigated in oxidizing and inert atmospheres revealing the stability of the trinuclear core up to 170 and 220°C, respectively.

Heterotrinuclear Ring Opening Copolymerization Catalysis: Structure–activity Relationships

Heteronuclear complexes are highly active catalysts in alternating ring opening copolymerizations (ROCOP) of cyclohexene oxide (CHO)/carbon dioxide or CHO/phthalic anhydride (PA). In this contribut...

Unprecedented deca-, penta- and poly-heteronuclear complexes with hexacyanometallates and 2-(hydroxymethyl)pyridine

The reactions of hexacyanometallates (Fe(III) and Co(III)) and 2-(hydroxymethyl)pyridine (hmpy) with ZnCl2 and CdCl2 affords the decanuclear [Cd6(hmpy)12Fe2(μ-CN)8(CN)4Fe2(μ-CN)4(CN)8] complex (1), the pentanuclear [Cd3(hmpy)6Co2(μ-CN)6(CN)6] cage complex (2) and the 3D framework [Zn(hmpy)2Zn2(hmpy)2Co2(µ-CN)8(CN)4]n (3). These new cyanide-bridged heteronuclear complexes have been characterised by FT-IR and Raman spectra, together with thermal and elemental analyses. Their structures have been determined by single crystal X-ray diffraction (SC-XRD) and powder X-ray diffraction (PXRD) analyses. In 1, the Cd(II) and Fe(III) centers are arranged alternately at the four corners of a rhombic core, and the cyanide ligands coordinate to the four metal centers of this core in the bridging mode. Adjacent tetranuclear rhombic cores further extend to a decaheteronuclear cluster structure via bridging cyanide ligands. Complex 2 has a pentaheteronuclear cage structure and the neighboring two Co(III) and three Cd(II) centers are bridged by six cyanide ligands. Complex 3 features an unprecedented 3D heterometallic Co(III)-Zn(II) framework based on cyanide ligands.

Mono- and oligonuclear complexes based on a o-vanillin derived Schiff-base ligand: Synthesis, crystal structures, luminescent and electrochemical properties

A new synthetic approach for homo- and heteronuclear complexes, based on N,N′-bis[(3-methoxysalicylideneamino)-propyl]-piperazine (H2L) Schiff-base ligand, has been developed. The ligand has been crystallized in the form H2L·2DMSO and its structure has been solved. Using this ligand, the following complexes have been synthesized: [CoL](ClO4) (1), [Zn2L(CH3COO)2]·2H2O (2), [Cu3L2(NO3)2] (3) and [LaCu6L4(H2O)2(NO3)2](NO3)5·15H2O (4). The 1–4 complexes were characterized by elemental analysis, X-ray crystallography, infrared and diffuse reflectance spectroscopy. The crystallographic investigations revealed that H2L presents the stable chair conformation of the piperazine ring, while its coordination mode changes according to the nature of the metal ion and counterion, respectively, allowing the formation of mono- (1) and oligonuclear (2–4) complexes. Compound 1 consists of a mononuclear complex cation, where the double-deprotonated ligand (L2−) encapsulates the trivalent cobalt ion. In compound 2, L2− acts as a symmetrical binucleatig ligand through the two N2O sets disposed on each side of the piperazine ring and coordinates two zinc(II) ions. Compounds 3 and 4 contain trinuclear units where two ligand molecules coordinate unsymmetrically three CuII ions, with the N3O donor set wrapped around the peripheral CuII and the remaining NO sets bound to the central CuII ion. Two such trinuclear moieties coordinate the LaIII ion in crystal 4. Electrochemical behavior of compounds 1 and 3 and luminescent properties of compound 2 are discussed.

Highly Coordinated Heteronuclear Calcium-Iron Carbonyl Cation Complexes [CaFe(CO)n ]+ (n=5-12) with d-d Bonding.

Heteronuclear calcium–iron carbonyl cation complexes in the form of [CaFe(CO)n]+ (n=5–12) are produced in the gas phase. Infrared photodissociation spectroscopy in conjunction with quantum chemical calculations confirm that the n=10 complex is the coordination saturated ion where a Fe(CO)4 fragment is bonded with a Ca(CO)6 fragment through two side‐on bridging carbonyl ligands. Bonding analysis indicates that it is best described by the bonding interactions between a [Ca(CO)6]2+ dication and an [Fe(CO)4]− anion forming a Fe→Ca d−d dative bond in the [(CO)6Ca–Fe(CO)4]+ structure, which enriches the pool of experimentally observed complexes of calcium that mimic transition metal compounds. The molecule is the first example of a heteronuclear carbonyl complex featuring a d−d bond between calcium and a transition metal.

Highly Coordinated Heteronuclear Calcium–Iron Carbonyl Cation Complexes [CaFe(CO)n]+(n=5–12) with d−d Bonding

AbstractHeteronuclear calcium–iron carbonyl cation complexes in the form of [CaFe(CO)n]+(n=5–12) are produced in the gas phase. Infrared photodissociation spectroscopy in conjunction with quantum chemical calculations confirm that then=10 complex is the coordination saturated ion where a Fe(CO)4fragment is bonded with a Ca(CO)6fragment through two side‐on bridging carbonyl ligands. Bonding analysis indicates that it is best described by the bonding interactions between a [Ca(CO)6]2+dication and an [Fe(CO)4]−anion forming a Fe→Ca d−d dative bond in the [(CO)6Ca–Fe(CO)4]+structure, which enriches the pool of experimentally observed complexes of calcium that mimic transition metal compounds. The molecule is the first example of a heteronuclear carbonyl complex featuring a d−d bond between calcium and a transition metal.

SYNTHESIS AND SPECTRAL CHARACTERISTICS OF HETEROMETALLIC COMPLEXES OF Pr(III) WITH Zn(II), CO(II) BASED ON ETHYLENEDIAMINETETRAACETIC AND ETHYLENEDIAMINEDISUCCINIC ACIDS

New heterometallic f-d-complexes of Pr (III), Co(II), Zn(II) with aminopolycarboxylic acids (ethylenediaminetetraacetic, ethylenediaminedisuccinic acids) have been synthesized and spectroscopically characterized. It was found that complexes with a molar ratio of Pr:M3d: EDTA=1:2:2 are formed for ethylenediaminetetraacetic compounds, and that in the case of complexes based on EDDS, heteronuclear compounds of the equimolar composition Pr: M3d: EDDS = 1: 1: 1 are formed. It is shown that it is expedient to carry out the synthesis of heterometallic complexes on the basis of mono­nuclear polycarboxylates of 3d metals, which act as a «building block» for the preparation of a heterobinuclear compound by the exo coordination of additional metal ions. The complexes are characterized by the method of electron absorption spectroscopy. It is shown that independent of 3d-metal, for both heterometallic systems based on EDDS, a hypsochromic shift of the absorption maxima relative to νmax is observed for the homonuclear praseodymium complex. For ethylenediaminetetraacetate systems, the absorption maxima undergo both low- and high-frequency shift, which indicates the different nature of the ligand field effect, which is caused primarily by differences in the structure of the corresponding heteronuclearaminopolycarboxylates due to the presence of a chiral carbon atom in the EDDS molecule. For the supersensitive transitions Pr(III)) 3H4 →3P2 and 3H4 → 1D2 , the covalence parameters of the Ln-O bond have been calculated: osci­llator power (P), nepheloxetic parameter (β), covalence parameter (b1/2), Sinha parameter (δ). Analysis of the spectroscopic parameters indicates a decrease in the covalence of the lanthanide-ligand bond in the transition from mono- to heteronuclear complex, and a decrease in the local symmetry of the lanthanide ion occurs in the order Ln (III) aqua ion <hete­rometallic complex <monometallic complex. Heteronuclear complexes are several orders of magnitude more stable than mononuclear ones due to the formation of additional bonds or metallacycles with donor ligand atoms. It is noted that the stability of complexes with EDDS is lower than that of the corresponding complexes with EDTA due to the different size and number of chelated metallacycles. The obtained heteronuclear complexes belong to folded complexes, in which the ligand-complexone realizes the maximum denticity to the lanthanide ion, and the coordination sphere of the 3d-cation is formed by carboxyl groups EDTA / EDDS and inner-sphere water molecules. In this case, the ions of 3d-metals are in a distorted octahedral environment, and the coordination number of Pr(III) is 8.

Synthesis, spectroscopic characterization, and SC-XRD study of one privileged heteronuclear Ni(II)/Hg(II)-Salen complex: An exclusive DFT outlook

A novel heteronuclear Salen complex, [NiHgCl2(L)] (1) (H2L = N,N′-bis(3-methoxysalicylidene)-2,2-dimethylpropane-1,3-diamine) has been integrated using two different synthetic lines. The complex is characterized by various spectroscopic techniques, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and single-crystal X-ray diffraction (SC-XRD). Powder X-ray diffraction (PXRD) confirms complex phase purity and crystallinity. The scanning electron microscope and energy-dispersive X-ray analysis (SEM-EDX) identified the element’s chemical composition, morphology, and crystal size. X-ray diffraction revealed ligand released phenoxide-type deprotonated form [L]2− and had spent two pockets, N2O2 pocket occupied by Ni(II) comprises square planar geometry (NiN2O2). In contrast, Hg(II) occupies a large open O4 compartment accompanied by two chloride ions (HgO4Cl2), switching to achieve a trigonal prismatic structure. The close surveillance of the crystal structure discloses various non-covalent interactions like H-bonding, CH⋯π, and π⋯π. The complex’s geometry was fully optimized, employing the quantum chemistry method at the DFT/B3LYP with the 6-31G (d, p) basis set to divine the vibrational spectra, NMR chemical shifts, and solvent effect on the electronic properties. Natural Bond Orbital (NBO) dissected the stability of the molecular structure and the intermolecular orbital interactions. The highest stabilizing energy was 132.84 kcal/mol between the lone pair C12 and the antibonding of N7-C17 atoms. The Hirshfeld Surface (HS) is detectable that the H⋯N input is maximum than H⋯O. The electrophilic-nucleophilic sites, non-covalent interactions, and reactivity were investigated based on Molecular Electrostatic Potential (MESP), Reduced Density Gradient (RDG), atoms in a molecule (AIM), and the HOMO-LUMO difference. Eventually, a significant correlation was anticipated between theoretical and experimental spectroscopic criteria.

Functionalized Trifluoromethyl-Containing Lithium β-Diketonate in the Synthesis of Homo- and Heteronuclear Complexes of Rare-Earth Metals

The reactions of functionalized lithium CF3-β-diketonate (LiL) with trivalent rare-earth metal salts in methanol afford homobinuclear and heterobi(tri)nuclear complexes depending on the nature of the transition metal and anion (chlorides, nitrates, and acetates). In the cases of lanthanum(III) and cerium(III), homoleptic complexes [(LnL3)2] are isolated (CIF files CCDC nos. 2031097 (Ia) and 2031102 (Ib)). The reaction of LiL with praseodymium(III) nitrate gives the new trimetallic structure [(LiPrL3)(LiL)(NO3)(H2O)2] (CIF file CCDC no. 2031103 (II)), and the replacement of nitrate by chloride gives [(PrL3)(LiL)(H2O)] (CIF file CCDC no. 2031104 (IIIa)). Regardless of the nature of the anion of the salt in the series from neodymium(III) to ytterbium(III) and yttrium(III), Ln–Li β-diketonates [(LnL3)(LiL)(solv)] (solv is H2O and MeOH) are formed, and their structures are characterized by X-ray structure analysis (CIF files CCDC nos. 2031099 (IIIb), 2031100 (IIIc), 2031098 (IVa), 2031096 (IVc), 2031094 (IVf), 2031101 (IVg), and 2031095 (IVh)). The equilibrium of the diketonate isomeric forms in a solution of deuterated dimethyl sulfoxide is studied by 19F NMR spectroscopy, and the qualitative composition of the polynuclear complexes is determined by mass spectrometry.

Developing A Novel Coumarone-Phenyl Amide Functionalized [Gd(III)-Pt(IV)] Complex as High T1, T2 Relaxive M-MRI Contrast Agent for Cancer Diagnosis

Pt(IV) cored Gd(III) metal complex as a multimodal MRI contrast agent for cancer diagnosis is reported. The hetero nuclear complex [Pr-(DO3-Ch-Ph-Am-Gd(III))2Pt(II)] is highly soluble in water and stable at room temperature. The complex shows high longitudinal (r1p = 24.43 mM-1 s-1) and transversal (r2p = 38.61 mM-1 s-1) relaxivity values in neat aqueous solution at pH =7 and at 27 oC. The relaxivity value of the complex is greater than the low molecular weight, FDA approved MRI contrast agents. The presence of two water molecules in the first coordination sphere and a replaceable hydrogen atom in the linker enhances the proton relaxation rate and gives a huge relaxivity value. The r2p/r1P ratio of 1.58 confirms that the complex is a T1-weighted contrast agent. The presence of high polar coumarone pendant arm and high rigid acridone moieties in the complex make the complex as better anticancer agent for ovarian cancer. The high polar nature of the coumarone, phenyl amide, acridone moiety will show better binding efficiency with ovarian cancer creating CA125 glycoprotein.

Elaborate Design of d8-d10 Heteronuclear Phosphors for Ultrahigh-Efficiency Solution-Processed Organic Light-Emitting Diodes.

Highly soluble d8-d10 heteronuclear phosphors afford an alternative approach to achieve high-efficiency organic light-emitting diodes (OLEDs) through a solution process. In this work, four highly phosphorescent d8-d10 heteronuclear complexes with significant Pt-Au interactions were prepared. By judicious selection of sterically hindered and π-conjugated substituents in triphosphine ligands, the phosphorescence is dramatically promoted through effectively prohibiting nonradiative thermal relaxation with an efficiency of 0.94-0.99 in doping films. Exploiting highly emissive Pt-Au complexes as phosphorescent dopants, ultrahigh-efficiency solution-processed OLEDs were attained. The peak current efficiency, power efficiency, and external quantum efficiency are 96.2 cd A-1, 65.0 lm W-1, and 26.4% for the green-emitting PtAu2 phosphor and 68.6 cd A-1, 42.5 lm W-1, and 25.1% for the orange-emitting Pt2Au phosphor, which represent the state-of-art for solution-processed OLEDs based on non-iridium phosphors.

Synthesis and study of mixed-ligand heteronuclear complexes of lanthanum (III) and cobalt (II) or nickel (II) with acetylacetone and α,α'-dipyridyl

New mixed-ligand heteronuclear complexes of lanthanum and cobalt (nickel) with acetylacetone (НАА) and α,α'-dipyridyl were synthesized and investigated by physic-chemical methods of analysis (elemental analysis, differential thermal analysis, IR and UV–VIS spectroscopy, X-ray powder diffraction). It was established that the obtained complexes have the same composition of the general formula – LаМ(AA)5·2α,α'-dipy, where М - Co, Ni, and 3d-metal ions are in a distorted octahedral environment. It was shown that the complexes have low (∼350 °С) temperatures of decomposition and form cobaltate (nickelate) of lanthanum with good phase uniformity. This method of obtaining complex oxides can significantly reduce the duration and energy consumption of their synthesis (compared to traditional ceramic methods).

Modulating the carrier transport of PtAg2 heteronuclear complexes to attain highly efficient OLEDs with narrow-band emission

Narrow-band emission in both photoluminescence and electroluminescence was achieved for PtAg2 heteronuclear complexes with FWHM values of 25 and 31 nm, respectively.

Novel Ru(II)/Os(II)‐Exchange Homo‐ and Heterometallic Polypyridyl Complexes with Effective Energy Transfer

AbstractTwo novel homometallic Ru−Ru and heterometallic Ru−Os dimers and trimers, [MII(bpy)2(4‐tpy‐4′‐methyl‐2,2′‐bipyridine)MII(tpy)]4+ and [MII(bpy)2](4‐tpy‐4′‐tpy‐2,2′‐bipyridine)(MII(tpy))2]6+, have been first prepared and characterized. Electrochemical properties of the metal‐based reversible oxidation and ligand‐based reduction are measured. Spectroscopic analysis of these complexes exhibits for every Ru‐ or Os‐based subunit an individual intense absorption spectrum extended over the entire UV and visible region. The heteronuclear complexes [RuII(bpy)2(4‐tpy‐4′‐methyl‐2,2′‐bipyridine)OsII(tpy)]4+, [RuII(bpy)2](4‐tpy‐4′‐tpy‐2,2′‐bipyridine)(OsII(tpy))2]6+, and [OsII(bpy)2](4‐tpy‐4′‐tpy‐2,2′‐bipyridine)(RuII(tpy))2]6+ display a weak emission spectrum in the near‐infrared region (NIR). The luminescence of the polynuclear assemblies is quantitatively quenched, by intramolecular energy transfer to the lower‐lying metal‐to‐ligand charge transfer (3MLCT) and metal‐centered (3MC) state of the Os(II)‐based center or Ru(II)‐terpyridine moiety at room temperature.