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Abstract

Two novel heterometallic complexes [Cu(bpy) 2 V 2 O 2 (O 2 ) 2 (R-mand) 2 ][Cu(bpy) 2 V 2 O 2 (O 2 ) 2 (S-mand) 2 ]·2CH 3 CN·2H 2 O (1), and [Cu(phen) 2 V 2 O 2 (O 2 ) 2 (R-mand) 2 ][Cu(phen) 2 V 2 O 2 (O 2 ) 2 (S-mand) 2 ]·2CH 3 CN·2H 2 O (2), (mand = mandelato(2–) = C 6 H 5 CH(O)CO 22– ) were prepared and characterized by spectral methods. X-ray single-crystal analysis revealed the difference between both structures. While 1 contains a bonding copper(II) and vanadium(V) atoms through the bridging oxygen atom Cu–O–V, the metallic atoms are connected in 2 through the carboxylic group Cu[sbnd]O[sbnd]C[sbnd]O[sbnd]V. Complexes 1 and 2 are immediately decomposed in their aqueous solutions, but their integrity is preserved for some time in DMSO. ⁵¹ V NMR spectra of DMSO solutions of vanadates(V), peroxidovanadates(V) and vanadium(V) mandelato complexes are presented for the first time.

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... In recent years, we have reported on transition metal-vanadium compounds, comprised of the combinations Mn-V [20], Fe-V, Ni-V [21,22] and Cu-V [23][24][25][26][27][28][29] that were investigated mostly for their chiral properties. In continuation of our studies on stereochemistry of vanadium(V) complexes, we present here the synthesis and characterization of [Ni(phen) 3 ...
... The Ni-N distances and N-Ni-N angles in the [Ni(phen) 3 ] 2+ cations point to slightly irregular octahedral geometry. The molecular structure of the [(V 2 O 2 (O 2 ) 2 (mand) 2 )] 2− anion was previously reported for few vanadium(V) peroxido complexes [29,34,35]. Both vanadium atoms adopt pentagonal pyramidal coordination geometry and are coordinated by one oxido ligand in the apical position as well as two oxygen atoms of the peroxido ligands and one oxygen atom of the carboxylate group of the mandelato ligand in the pentagonal pseudoplane. ...
... (ii) The intensity of signals increases at the beginning, then decreases. This behaviour concerns the signals at −540, −534 and −511 ppm, which can be assigned to peroxidovanadium species (without mandelic acid) [29] and a signal at −495 ppm attributable to monoperoxido mandelato complexes of vanadium [29]. (iii) The intensity of only one signal increases continually with time. ...
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A nickel‒vanadium metal–organic hybrid compound [Ni(phen)3]2[(V2O2(O2)2((S)-mand)2)][(V2O2(O2)2((R)-mand)2)]·18H2O (phen = 1,10-phenanthroline, mand²⁻ = mandelato(2−) ligand, C6H5–CO–COO²⁻) (1) was prepared and characterized by spectral methods, X-ray structure analysis and simultaneous DTA and TG measurements. The crystal structure of 1 contains both Δ and Λ enantiomers of the [Ni(phen)3]²⁺ cations that construct sandwich layers along the crystallographic axis c, in between which sit the vanadium(V) complex anions. These are present as ionic dimers in the form of a robust {[(V2O2(O2)2((S)-mand)2)][(V2O2(O2)2((R)-mand)2)]}⁴⁻ species. The two individual anions are coupled by a pair of weak, yet significant attractions between two vanadium atoms and two peroxido ligands of the adjacent anion at V‒O distances 2.660 Å. The ⁵¹V NMR spectrum of the compound in DMSO solution revealed a complicated course of decomposition reactions of the anion, which led to formation of the [(V2O4(S,R-mand)2]²⁻ anion as a single product. The metal–organic hybrid compound 1 is converted by thermal decomposition into a potential anode material for lithium-ion batteries Ni(VO3)2.
... [Cu(im) 4 (V 2 O 4 (mand) 2 ] n (1) and [Cu(im) 4 (V 2 O 4 ((S)mand) 2 )] n ·2nH 2 O (2) (mand = mandelato(2-) ligand) were prepared as a part of our continual research on heterometallic transition metal-vanadium compounds with potential applications in asymmetric catalysis or development of new anode materials for batteries [4,[6][7][8][9]. Herein, we discuss the unexpected polymeric structures of 1 and 2 that differ significantly from the heretofore characterized, mostly chiral, compounds. ...
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Two new 1D polymeric heterometallic copper–vanadium compounds were prepared. The polymers are constructed from [Cu(im)4]²⁺ cations that are coordinated to two terminal oxido ligands of [V2O4(mand)2]²⁻ anions. The stronger coordination in [Cu(im)4V2O4(mand)2]n (1) that contains the racemic mandelato ligand is manifested by a shorter Cu‒O bond distance 2.4095(12) Å, while the weaker interaction in [Cu(im)4(V2O4((S)-mand)2)]n·2nH2O (2) is exhibited by Cu‒O bond distances 2.4547(16) Å and 2.5413(16) Å. The vanadate anion in compound 2 carries only the (S)-enantiomer of the initial mandelic acid and differs from the anion in 1 in parallel cis orientation of the phenyl groups of the mandelato ligand. FT-IR spectroscopy was used for the confirmation of the coordination mode of mandelato ligand. Strong bands corresponding to the vibrations of carboxyl groups can be observed around 1650 and at 1344 cm⁻¹. The stretching vibration of deprotonated hydroxyl group in the mandelato ligand occurs at 1045 and 1065 cm⁻¹ for 1 and 2, respectively. In addition, the very strong, characteristic band corresponding to ν(V=O) vibration can be observed at 931 cm⁻¹ for 1 and 925 cm⁻¹ for 2, as well as in Raman spectrum. Graphic Abstract The polymeric structures of two new vanadium-copper heterometallic complexes are constructed from [Cu(imidazole)4]²⁺ cations that are coordinated to two terminal oxido ligands of [V2O4(mandelato)2]²⁻ anions with different orientation of the phenyl groups depending on the chirality of the mandelato ligand. Open image in new window
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Nine mononuclear metal complexes of monoanionic α-hydroxycarboxylates (HL′) with imidazole as a co-ligand have been synthesised and structurally characterized by X-ray diffraction. The nickel(II) complexes can be described by two formulae: [Ni(HL′)2(Im)2], HL′=2-methyllactate (HmL) (1) or mandelate (HM) (2), and [Ni(HB)2(Im)3], HB=benzylate (3). In these compounds the nickel atom is in a distorted octahedral environment. The copper(II) complexes of the general formula [Cu(HL′)2(Im)], HL′=glycolate (HG) (4), lactate (HL) (5) or 2-methyllactate (HmL) (6) presents a square pyramidal coordination geometry with a distortion evaluated in terms of the τ parameter. The zinc(II) complexes have the general formula [Zn(HL′)2(Im)2]·xH2O, HL′=lactate (HL) and x=1/2 (7), 2-methyllactate (HmL) and x=0 (8) and display a distorted octahedral geometry. However, the reaction with H2B afforded the imidazole complex [Zn(Im)6](HB)2, HB=benzylate (9), which has two uncoordinated benzylate units. In most of the complexes the α-hydroxycarboxylato ligands behave as bidentate monoanionic systems, apart from in 3, where one ligand is monodentate. All of the complexes are extended into 2D or 3D frameworks through hydrogen bonding. The complexes were also characterized by elemental analysis, FT-IR and UV/Vis spectroscopy. The nickel and copper compounds were also studied by room temperature magnetic susceptibility and room temperature ESR spectra were obtained for the copper compounds. Finally, the thermal behaviour of all the compounds was investigated.
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Medium basis sets based upon contractions of Gaussian primitives are developed for the third-row elements K through Zn. The basis functions generalize the 6-31G and 6-31G∗ sets commonly used for atoms up to Ar. They use six primitive Gaussians for 1s, 2s, 2p, 3s, and 3p orbitals, and a split-valence pair of three and one primitives for valence orbitals, which are 4s and 5p for atoms K and Ca, and 4s, 4p, and 3d for atoms Sc through Zn. A 6-31G∗ set is formed by adding a single set of Gaussian polarization functions to the 6-31G set. They are Cartesian d-functions for atoms K and Ca, and Cartesian f-functions for atoms Sc through Zn. Comparison with experimental data shows relatively good agreement with bond lengths and angles for representative vapor-phase metal complexes. © 1998 American Institute of Physics.
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We report re-optimization of a recently proposed long-range corrected (LC) hybrid density functional [J.-D. Chai and M. Head-Gordon, J. Chem. Phys., 2008, 128, 084106] to include empirical atom–atom dispersion corrections. The resulting functional, oB97X-D yields satisfactory accuracy for thermochemistry, kinetics, and non-covalent interactions. Tests show that for non-covalent systems, oB97X-D shows slight improvement over other empirical dispersion-corrected density functionals, while for covalent systems and kinetics it performs noticeably better. Relative to our previous functionals, such as oB97X, the new functional is significantly superior for non-bonded interactions, and very similar in performance for bonded interactions.
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Detailed and thorough potentiometric and 51V-NMR spectroscopic investigations of H+–H2VO4−–H2O2–Ligand systems have been performed at 25 °C in 0.15 M Na(Cl) ionic medium. Extensive ranges of vanadate, hydrogen peroxide and ligand concentration and of pH have been covered. The medium was chosen to represent the physiological conditions in human blood. The computer program lake, designed to treat different types of data simultaneously, has been used to establish the entire speciation in the systems. Before studying systems containing the ligand (L), the complete speciation in the subsystem H+–H2VO4−–H2O2 must be known under the same experimental conditions. The formation constants in this subsystem have earlier been determined and it was found that hydrogen peroxide interacts with vanadate in the whole pH range studied (0.5–10.5). In all, 10 peroxovanadate species were identified and diperoxovanadate species were found to be exceptionally stable at physiological pH. The ligands studied so far include imidazole (Im), l-α-alanyl-l-histidine (Ah), l-α-alanyl-l-serine (As), picolinic acid (Pi), and l-(+)-lactic acid (La). In these five systems, as many as 3, 8, 6, 8, and 5 different peroxovanadate—L species (isomers included) were identified. A feature common to all these systems is that V(H2O2)2L species are formed at physiological pH. Notably, the 51V chemical shift values of diperoxovanadate moieties are always found in the range −670 to −770 ppm, and those of monoperoxovanadate from −540 to −670 ppm. The equilibrium conditions are illustrated in distribution diagrams and the effectiveness of the different ligands as complexation agents are compared. In the case of diperoxovanadate complexes, ligands with aromatic nitrogen (Im, Pi, Ah) are the most effective, the one with both aliphatic nitrogen and oxygen (As) is less effective, and the one with oxygen only (La) is the least preferred.
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The new heterometallic, mixed-valence compound [Cu2(bpy)4(C2O4)][(VO)2O(bpy)2(C2O4)2]2·10H2O has been synthesized, its crystal structure determined and its spectroscopic characterization accomplished by means of solid-state vibrational (far and mid FTIR) spectroscopy. The title compound crystallises in the triclinic system, space group P1¯ (No. 2) [a = 13.488(5) Å, b = 14.160(6) Å, c = 15.829(9) Å, α = 87.22(2)°, β = 66.33(2)°, γ = 64.49(2)°, V = 2471(2) Å3, Z = 1]. The compound consists of the cationic binuclear copper(II) complex [Cu2(bpy)4(C2O4)]2+, two anionic binuclear mixed valence vanadium(IV)−vanadium(V) complexes [(VO)2O(bpy)2(C2O4)2]−, and ten uncoordinated water molecules. The copper atom exhibits a Jahn−Teller-distorted octahedral coordination. The vanadium atoms adopt a strongly distorted octahedral coordination and form a characteristic O=V−O−V=O moiety with a significantly bent V−O−V link. The temperature dependence of the magnetic susceptibilities has been investigated in the temperature range 2−300 K and explained in terms of the ferromagnetic interaction between CuII ions giving J = 22.7 yJ (1.14 cm−1) and g = 2.014.
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A series of MnII, FeII, CoII, NiII and CuII layered mandelates has been synthesised in the form of crystalline powders by a hydrothermal route. The five compounds are isostructural with the copper analogue, also obtained in a single crystal form, except that the latter shows a strong Jahn−Teller distortion of the coordination spheres around the CuII centres. The complexes crystallise in the monoclinic centrosymmetric space group P21/a and their structures consist of layers of six-coordinate metal(II) ions interconnected through carboxylato bridges in a diamond-like network. The magnetic data indicate very small antiferromagnetic in-plane couplings for 1, 2, 3 and 5, with J/kB = −0.122 K for 1. The NiII compound 4 exhibits ferromagnetic coupling within the layers (J/kB = +1.213 K) and ferromagnetic 3D ordering can be observed at TC = 2.7 K. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Article
A novel chiral coordination polymer, [Cu(C(6)H(5)CH(OH)COO)(μ-C(6)H(5)CH(OH)COO)] (1-L and 1-D), was synthesized through a reaction of copper acetate with L-mandelic acid at room temperature. Although previously reported copper mandelate prepared by hydrothermal reaction was a centrosymmetric coordination polymer because of the racemization of mandelic acid, the current coordination polymer shows noncentrosymmetry and a completely different structure from that previously reported. The X-ray crystallography for 1-L revealed that the copper center of the compound showed a highly distorted octahedral structure bridged by a chiral mandelate ligand in the unusual coordination mode to construct a one-dimensional (1D) zigzag chain structure. These 1D chains interdigitated each other to give a layered structure as a result of the formation of multiple aromatic interactions and hydrogen bonds between hydroxyl and carboxylate moieties at mandelate ligands. The coordination polymer 1-L belongs to the noncentrosymmetric space group of C2 to show piezoelectric properties and second harmonic generation (SHG) activity.
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Polarization functions are added in two steps to a split-valence extended gaussian basis set: d-type gaussians on the first row atoms C. N, O and F and p-type gaussians on hydrogen. The same d-exponent of 0.8 is found to be satisfactory for these four atoms and the hydrogen p-exponent of 1.1 is adequate in their hydrides. The energy lowering due to d functions is found to depend on the local symmetry around the heavy atom. For the particular basis used, the energy lowerings due to d functions for various environments around the heavy atom are tabulated. These bases are then applied to a set of molecules containing up to two heavy atoms to obtain their LCAO-MO-SCF energies. The mean absolute deviation between theory and experiment (where available) for heats of hydrogenation of closed shell species with two non-hydrogen atoms is 4 kcal/mole for the basis set with full polarization. Estimates of hydrogenation energy errors at the Hartree-Fock limit, based on available calculations, are given.
The separation of amygdalin, prunasin and their isomers neoamygdalin and sambunigrin could be achieved with micellar capillary electrophoresis (MEKC). The two isomers were obtained in alkaline conditions and were produced in less than 15 min at pH 11.0. The developed methods showed a good selectivity in the separation of the isomers only in the presence of SDS micelles. The working pH was optimized to allow best resolution and quantitative analysis of these compounds. With a linear calibration over an injection time from 1 to 20 s, the detection limit was found to be in the range of 5 microM (S/N=3; 20 s injection time). Two pH buffer systems (pH 5.2 and pH 9.1) were chosen to confirm the peak attributions of the compounds in the apple and peach seeds samples. Sambunigrin was found in both apple and peach seeds but could not be quantified because of missing standards. Prunasin and amygdalin were not found in the apple sample, while they were quantified in the peach seeds in concentrations of 50 microg/g and 90 microg/g (dry weight), respectively.
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The crystal structure of the title complex, bis­(tetra-n-butyl­ammonium) bis(--hydroxy­benzene­acetato)-1κ2O1,O2:2κO2;1κO2:2κ2O1,­O2-bis­[oxo­(peroxo)­vanadium(V)] α-hydroxy­benzene­acetic acid solvate, (C16H36N)2­[V2O2(O2)2(C8H6O3)2]·C8H8O3, consists of dimeric anions with twofold rotation symmetry, cations and mol­ecules of mandelic acid. Deprotonated hydroxyl O atoms of the mandelate dianion ligands bridge the V atoms to give a non-planar V2O2 ring. Each V atom has distorted pentagonal pyramidal coordination geometry, with an oxo ligand in the axial position. The mandelic acid mol­ecule is disordered and coordinates weakly to the second axial site of each V atom through a carboxyl­ate O atom.
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Tetranuclear complexes [NiII2VV2(RCOO)2(L¹)2O4] (1 and 2) have been isolated from a single-pot synthesis by the reaction of [Ni(H2L¹)(RCOO)2] precursors (H2L¹ is a phenol-based tetradentate N2O2 ligand) with tetrabutylammonium decavanadate in an acetone/CH3CN (1:1, v/v) solvent mixture. The core structure of these molecules has a centrosymmetric heterometallic eight-membered Ni2V2O4 ring stabilized by alternating oxo and phenoxo bridges. With β-diketonates as ancillary ligands, heterobinuclear complexes of composition [(β-diket)NiIIL¹VIVO(β-diket)] (3 and 4) have also been prepared and structurally characterized. Their magnetic, redox, and spectroscopic properties have been investigated in detail.
  • Beghidja