Crystal structures of chiral (R/S) (C<Subscript>8</Subscript>H<Subscript>11</Subscript>N)<Subscript>2</Subscript> · Zn(OAc)<Subscript>2</Subscript>

Two opposite configuration (R/S) of chiral complexes (C₈H₁₁N)₂ · Zn(OAc)₂ (Ia and Ib—L-(−)-) and D-(+)-isomer) were synthesized by a simple one-pot method. The crystal structures of Ia and ib determined by X-ray crystallography.     

Preparation,spectroscopic and magnetic characterization of Cu(cyclam)M(CN)<Subscript>4</Subscript> complexes exhibiting one-dimensional crystal structures (cyclam = 1,4,8,11-tetraazacyclotetradecane,M = Ni,Pd, Pt)

From the systems Cu(II)–cyclam–[M(CN)₄]^2? (cyclam = 1,4,8,11-tetraazacyclotetradecane; M = Ni, Pd, Pt), three cyanidocomplexes Cu(cyclam)M(CN)₄ [M = Ni (1), Pd (2), Pt (3)] were isolated and characterized by chemical analysis, IR and UV–VIS spectroscopy. The three compounds are isostructural, and their crystal structures are formed by quasi-linear chains exhibiting [–Cu(cyclam)–μ–NC–M(CN)₂–μ–CN–]_n composition. The Cu(II) atoms reside on centres of symmetry and are coordinated in the form of an elongated octahedron with mean equatorial Cu–N bonds of 2.015(12), 2.017(13) and 2.011(11) Å in (1), (2) and (3), respectively, and weakly N-bonded bridging cyanido ligands in the axial positions [2.5321(9) Å in (1), 2.518(2) Å in (2) and 2.549(3) Å in (3)]. Hydrogen bonds of the N–H···N_cyanido···H–N type link neighbouring chains, and a topologically square network of paramagnetic Cu(II) atoms is formed. The magnetic susceptibilities of all three complexes follow the Curie-Weiss law with a weak antiferromagnetic exchange coupling below 5 K.     

Synthesis and Characterization of the Face-Centered Cubic Clusters [(Me<Subscript>3</Subscript>tacn)<Subscript>8</Subscript>M<Subscript>8</Subscript>Pt<Subscript>6</Subscript>(CN)<Subscript>24</Subscript>]<Superscript>12+</Superscript> (M = Cr,Mo)

Incorporation of a 5d transition metal into the face-centered cubic metal-cyanide cluster geometry is accomplished for the first time with the isolation of a series of compounds featuring [(Me₃tacn)₈M₈Pt₆(CN)₂₄]¹²⁺ (M = Cr, Mo) clusters. Reaction of [(Me₃tacn)Cr(CN)₃] and K₂[PtCl₄] in a boiling aqueous solution generates [(Me₃tacn)₈Cr₈Pt₆(CN)₂₄]Cl₁₂ · 27H₂O (1), wherein Pt^II centers reside at the face-centering sites and the cyanide ligands have reoriented to give Pt^II–C≡N–Cr^III linkages. The cyclic voltammogram obtained for a solution of 1 in DMSO exhibits a quasireversible reduction event centered at E _1/2 = ?1.59 V versus Cp₂Fe^0/1+. Reaction of 1 with K₂[Pt(CN)₄] in aqueous solution affords [(Me₃tacn)₈Cr₈Pt₆(CN)₂₄][Pt(CN)₄]₆ · 6H₂O (2), in which each face of the cubic cluster is capped by a staggered tetracyanoplatinate anion with a Pt–Pt separation of 3.1552(7) Å. Attempts to perform analogous cluster-forming reactions with [(Me₃tacn)Mo(CN)₃] revealed a tendency toward cluster decomposition to give mixtures of insoluble products, including [(Me₃tacn)₈Mo₈Pt₆(CN)₂₄][Pt(CN)₄]₆ · 46H₂O (3) and [(Me₃tacn)₈Mo₈Pt₆(CN)₂₄][Pt(CN)₄]_2.5[Pt(CN)₃Br]₂Br₃ · 6H₂O (4). Crystallographic analyses revealed these compounds to contain the anticipated [(Me₃tacn)₈Mo₈Pt₆(CN)₂₄]¹²⁺ cluster in fully- and partially-capped forms, respectively. Unfortunately, the insolubility of these molybdenum-containing products precluded characterization of the cluster by cyclic voltammetry.     

A theoretical investigation on the structures and stabilities of C<Subscript>60</Subscript>X<Subscript>18</Subscript> and C<Subscript>70</Subscript>X<Subscript>10</Subscript> (X = H,F, Cl,and Br)

A density functional theory study was performed on fullerene derivatives C₆₀X₁₈ and C₇₀X₁₀ (X = H, F, Cl, and Br). The calculated results show that the lowest energy isomers are IPR-satisfying for C₆₀X₁₈ (X = H, F, Cl, and Br). It is found that the addition patterns of X (X = Cl and Br) are different from those of X (X = H and F) for C₆₀, demonstrating that the stability of fullerene derivatives is partly attributed to the steric repulsion and electronegativity of added atoms. However, the lowest energy isomers are IPR-violating for C₇₀X₁₀ (X = H, F, and Cl), suggesting that many more fullerene derivatives may violate the isolated pentagon rule.     

Synthesis and structures of cationic μ-diborolyl triple-decker complexes [CpCo(1,3-C<Subscript>3</Subscript>B<Subscript>2</Subscript>Me<Subscript>5</Subscript>)M(C<Subscript>5</Subscript>R<Subscript>5</Subscript>)]<Superscript>+</Superscript> (M = Rh or Ir)

The cationic triple-decker complexes [CpCo(1,3-C₃B₂Me₅)M(C₅R₅)]⁺ (M = Rh (2), Ir (3), R = H (a), Me (b)) with the bridging diborolyl ligand were synthesized by the reaction of the sandwich anion [CpCo(1,3-C₃B₂Me₅)]^- (1) with the halide complexes [CpMI₂]₂ or [Cp^*MCl₂]₂ (Cp^* = C₅Me₅). The structures of [2b]PF₆ and [3b]PF₆ were established by X-ray diffraction. The nature of the metal—diborolyl bond in these complexes was analyzed using the energy decomposition scheme.     

Application of a modified Pechini method for the synthesis of Ln<Subscript>2</Subscript>MGe<Subscript>4</Subscript>O<Subscript>12</Subscript> (Ln = Y,Eu; M = Ca,Zn, Mn) optical hosts

A modified Pechini method followed by conventional and microwave heating was used to synthesise the new promising Ln₂MGe₄O₁₂ (Ln = Y, Eu; M = Ca, Zn, Mn) optical hosts. Comparison between solid-state and Pechini synthesis methods showed that the latter reduces the temperature required for cyclo-tetragermanate formation. The highest yield of cyclo-tetragermanates for both methods is observed at 1,000–1,100 °C, with significantly shorter time of annealing in the case of the Pechini synthesis. Compositional, structural and morphological characterisations of the samples obtained by both routes were carried out using X-Ray powder diffraction, thermogravimetry, electron spin resonance spectroscopy, energy-dispersive X-Ray spectroscopy and scanning electron microscopy.     

Theoretical studies on the infrared spectrum of the tetrahedral molecules R<Subscript>2</Subscript>MH<Subscript>2</Subscript> (R = D(H), CH<Subscript>3</Subscript>, OH; M = Ti,Zr, Hf)

Using Stuttgart/Dresden effective core potentials MWB28, MWB60, and GTO valence basis sets (8s7p6d)/[6s5p3d], (8s7p6d)/[6s5p3d] for Zr and Hf atoms and 6-311++G(3df,3pd) basis set for C, H, O, and Ti atoms, tight convergence criteria geometry optimizations and harmonic frequency calculations are performed at B3LYP and B3LYP/IEF-PCM levels of theory so as to model the gas phase and argon matrix infrared spectra of the tetrahedral molecules R₂MH₂ (R = D(H), CH₃, OH; M = Ti, Zr, Hf). Influence of the transition metal and/or substituent group on the symmetric and asymmetric stretching frequencies of the MH₂ fragment of the R₂MH₂ molecules is investigated at both the levels of theory. The modelling of the argon matrix effect improves the agreement between the calculated frequencies and the experimental ones. The calculated argon matrix to gas phase frequency shifts is compared reasonably to the experimental argon to neon matrix shifts.     

Crystal structure and vibrational spectra of M[VO<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>]·H<Subscript>2</Subscript>O (M = K,Rb, NH<Subscript>4</Subscript>)

By the hydration of MVO(SeO₄)₂ with saturated water vapors at room temperature a series of isostructural complex compounds of vanadium(V) of the composition M[VO₂(SeO₄)(H₂O)₂]·H₂O (K, Rb, NH₄) are synthesized and their physicochemical properties are studied. Based on the X-ray and neutron diffraction data, it is found that their crystal structure is composed of VO₆ octahedra linked in infinite chains by bridging SeO₄ tetrahedra. Each of the VO₆ octahedra has two short terminal V-O bonds forming a bent dioxovanadium group VO₂⁺. Two water molecules are coordinated by vanadium and one molecule is out of the first coordination sphere in the interchain space. The vibrational spectra of the studied compounds are completely consistent with their structural features.     

Zn<Subscript>0.97</Subscript>M<Subscript>0.03</Subscript>O (M = Co,Fe, and V) pigments: thermal,structural, and optical characterization

Zinc oxide is a widely used white inorganic pigment. Transition metal ions are used as chromophores and originate the ceramic pigments group. In this context, ZnO particles doped with Co, Fe, and V were synthesized by the polymeric precursors method, Pechini method. Differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques were used to accurately characterize the distinct thermal events occurring during synthesis. The TG and DSC results revealed a series of decomposition temperatures due to different exothermal events, which were identified as H₂O elimination, organic compounds degradation and phase formation. The samples were structurally characterized by X-Ray diffractometry revealing the formation of single phase, corresponding to the crystalline matrix of ZnO. The samples were optically characterized by diffuse reflectance measurements and colorimetric coordinates L*, a*, b* were calculated for the pigment powders. The pigment powders presented a variety of colors ranging from white (ZnO), green (Zn_0.97Co_0.03O), yellow (Zn_0.97Fe_0.03O), and beige (Zn_0.97V_0.03O).     

Geometric and electronic structure of an N,N′-ethylene-bis(salicylaldiminato) zinc(II) molecule,ZnO<Subscript>2</Subscript>N<Subscript>2</Subscript>C<Subscript>16</Subscript>H<Subscript>14</Subscript>

Gas electron diffraction at a temperature T of 641(5) K is used to study the structure of an N,N′-ethylenebis(salicylaldiminato) zinc(II) molecule, ZnO₂N₂C₁₆H₁₄, further Zn(salen). The structure of a gaseous Zn(salen) complex has C ₂ symmetry and is characterized by a substantial turn of two chelating fragments of the ligand with respect to each other, and also by a big difference in the length of coordination bonds: r _h1(Zn-O)=1.902(7) Å r _h1(Zn-N)= 2.027(7) Å. Results of the DFT/B3LYP calculation with 6-31G* and CEP,TZV basis sets of the molecule structure well agree with the experimental data. The electronic structure of Ni(salen), Cu(salen), Zn(salen), and Zn(acacen) molecules is considered.     

Exohedral Silicon Fullerenes: Si<Subscript>60</Subscript>Pn<Subscript>60</Subscript> and Si<Subscript>80</Subscript>Pn<Subscript>60</Subscript> (Pn = P,As, Sb and Bi)

Based on density functional theory (DFT) calculations, we predict that the icosahedral structures of the silicon fullerenes Si₆₀ and Si₈₀ can be stabilized by 12 exohedral pentagons of group V-A unit Pn₅ (Pn = P, As, Sb or Bi). The 12 pentagons can fully passivate the dangling bonds associated with 12 pentagonal Si₅ rings on the silicon fullerene cages, thereby resulting in stable exohedral silicon fullerenes Si₆₀Pn₆₀ and Si₈₀Pn₆₀. Properties of the eight Si₆₀Pn₆₀ and Si₈₀Pn₆₀ clusters, including harmonic vibrational frequencies, electron affinity (EA), the HOMO–LUMO gap and NICS values, are computed. We find that all eight Si₆₀Pn₆₀ and Si₈₀Pn₆₀ fullerenes possess relatively large HOMO–LUMO gaps, high electron affinities, and that the Si₆₀Pn₆₀ fullerenes exhibit weak aromaticity. Among eight clusters examined, the exohedral fullerene I _h-Si₆₀P₆₀ possesses the largest cohesive energy per atom. Ab initio molecular dynamics (AIMD) simulation is performed to demonstrate thermal stability of the hollow cage structure of Si₆₀P₆₀ at the room temperature.     

Synthesis and crystal structure of two {M(4,4′-dpdo)<Subscript>2</Subscript>[N(CN)<Subscript>2</Subscript>]<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>} complexes (M = Co(II), Mn(II); 4,4′-dpdo = 4,4′-bipyridyl-N,N′-dioxide)

The ligand 4,4′-bipyridyl-N,N′-dioxide (4,4′-dpdo) was used in the synthesis of two complexes, {Co(4,4′-dpdo)₂[N(CN)₂]₂(H₂O)₂} (1) and {Mn(4,4′-dpdo)₂[N(CN)₂]₂(H₂O)₂} (2). The complexes were found to be isostructural, triclinic, space group P-1 with Z = 1 and the following unit cell parameters: a = 8.158(8) Å, b = 8.865(8) Å, c = 9.477(9) Å; α = 70.988(13)°, β = 78.778(13)°, γ = 71.964(10)°; V = 612.8(10) ų for 1; a = 8.247(14) Å, b = 9.001(16) Å, c = 9.707(17) Å; α = 71.02(2)°, β = 78.63(2)°, γ = 72.62(2)°; V = 646(2) ų for 2. Final R-values were 0.075 and 0.083 for 1 and 2, respectively. In the molecules of the complexes, Co(II) or Mn(II) cation is coordinated by two O-atoms of two 4,4′-dpdo ligands, two terminal N-atoms of two dicyanamides, and two O-atoms of water molecules. The crystals are molecular, with adjacent complex molecules linked through a system of O-H...N and O-H...O hydrogen bonds.     

Interaction of hydantoins with transition metal ions: synthesis,structural, spectroscopic,thermal and magnetic properties of [M(H<Subscript>2</Subscript>O)<Subscript>4</Subscript>(phenytoinate)<Subscript>2</Subscript>] M = Ni(II), Co(II)

Complexes of Ni(II) and Co(II) of the formulae [Ni(H₂O)₄(pht)₂] (1) and [Co(H₂O)₄(pht)₂]·1,5NH₃·H₂O (2) (where pht = phenotoinate anion) were obtained and characterized physicochemically. [Ni(H₂O)₄(pht)₂] (1) crystallizes in a monoclinic space group P2₁/c; a = 11.7358(8), b = 11,1250(8), 11.4182(7) Å; β = 97.076(5)°; V = 1479.41 Å³; Z = 2. The environment around the nickel and cobalt ions can be described as a distorted octahedron. The metal ion was found to bind to four water molecules and two nitrogen atoms derived from two anions of the monodentate phenytoinate. Four intramolecular hydrogen bonds designated as S(6) graph set are found in one [Ni(H₂O)₄(pht)₂] (1) molecule. Two chain HB patterns, constructed by the [Ni(H₂O)₄(pht)₂] molecules extending along the c and b axes, respectively, have been observed. The cobalt complex precipitates with the additional solvent molecules: one and a half of ammonia and one water. The results document the preferential binding of hydantoins to the metal ions through N(3) atom.     

Direct synthesis of hydrogen peroxide from hydrogen and oxygen over insoluble Pd<Subscript>0.15</Subscript>M<Subscript>2.5</Subscript>H<Subscript>0.2</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> (M = K,Rb, and Cs) heteropolyacid catalysts

Palladium-containing insoluble heteropolyacid (HPA) catalysts (Pd_0.15M_2.5H_0.2PW₁₂O₄₀) were prepared by an ion-exchange method using various alkaline metal ions (M = K⁺, Rb⁺, and Cs⁺) (denoted as Pd-KPW, Pd-RbPW, and Pd-CsPW). They were then applied to the direct synthesis of hydrogen peroxide from hydrogen and oxygen. Conversion of hydrogen over the catalysts was almost identical with no great difference, while selectivity for hydrogen peroxide increased in the order of Pd-KPW < Pd-RbPW < Pd-CsPW. As a consequence, yield for hydrogen peroxide increased in the order of Pd-KPW < Pd-RbPW < Pd-CsPW. It was found that yield for hydrogen peroxide increased with increasing Pd 3d_5/2 binding energy of the catalyst. Among the catalysts tested, Pd-CsPW catalyst with the highest Pd 3d_5/2 binding energy showed the highest yield for hydrogen peroxide.     

Synthesis and physicochemical study of M<Subscript>4</Subscript>Na<Subscript>2</Subscript>V<Subscript>10</Subscript>O<Subscript>28</Subscript> · 10H<Subscript>2</Subscript>O (M=K,Rb, NH<Subscript>4</Subscript>)

The formation conditions and physicochemical properties of binary decavanadates M₄Na₂V₁₀O₂₈ · 10H₂O (M=K, Rb, NH₄), synthesized by crystallization from saturated solutions of the NaVO₃-MH₂AsO₄-H₂O systems, were studied by chemical analysis, X-ray powder diffraction, microscopy, thermogravimetry, and IR spectroscopy. To optimize the synthesis conditions of M₄Na₂V₁₀O₂₈ · 10H₂O, the ( 1-x)NaVO₃ · 2H₂O · xMH2AsO4-H₂O (0.2 ≤ x ≤ 0.8) isomolar series method was applied to studying the interaction in the NaVO₃-MH₂AsO₄-H₂O systems (M = K, Rb, Cs) at the 0.4 mol/L total molar concentration of NaVO₃ and MH₂AsO₄ in solutions. The studied M₄Na₂V₁₀O₂₈ · 10H₂O compounds were shown to be isostructural with triclinic crystals (Z= 1, space group P $ \bar 1 $ \bar 1 ), and their unit cell parameters were estimated.     

Synthesis and crystal structures of [K(H<Subscript>2</Subscript>O)(Piv)]<Subscript>∞</Subscript> and [K<Subscript>2</Subscript>(Phen)(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>(Piv)<Subscript>2</Subscript>]<Subscript>∞</Subscript>

A method for the synthesis of potassium pivalates (trimethylacetates) from potassium tert-butoxide and pivalic acid was proposed. The complexes of the formulas [K(H₂O)(Piv)]_∞(I) and [K₂(Phen)(H₂O)₂(Piv)₂]_∞ (II) (Piv denotes the pivalate anion and Phen denotes 1,10-phenanthroline) were obtained and characterized by elemental analysis and IR and ¹H NMR spectroscopy. The crystal structures of complexes I and II were determined using X-ray diffraction. Crystal structure I has a layered motif with two nonequivalent K atoms (C.N.s 5 + 2 and 6). The coordination of phenanthroline in II gives rise to a ribbon motif, the structure containing three nonequivalent K atoms (C.N.s 6, 6 + 1, and 8).     

σ-Hole bond tunability in YO<Subscript>2</Subscript>X<Subscript>2</Subscript>:NH<Subscript>3</Subscript> and YO<Subscript>2</Subscript>X<Subscript>2</Subscript>:H<Subscript>2</Subscript>O complexes (X = F,Cl, Br; Y = S,Se): trends and theoretical aspects

A σ-hole is defined as an electron-deficient region on the extension of a covalently bonded group IV–VII atoms. If the electronic density in the σ-hole is sufficiently low, then this region will have a positive electrostatic potential, which allows attractive noncovalent interactions with negative sites. SO₂X₂ and SeO₂X₂ (X = F, Cl and Br) have three Lewis acid sites of σ-hole located in the outermost of chalcogen atom and X end, participating in the chalcogen and halogen bonds with NH₃ and H₂O, respectively. MP2/aug-cc-pVTZ and M06-2X/aug-cc-pVTZ calculations reveal that for a given halogen atom, SeO₂X₂ forms stronger chalcogen bond interactions than SO₂X₂ counterpart. Almost a perfect linear relationship is evident between the interaction energies and the magnitudes of the product of most positive and negative electrostatic potentials. The interaction energies calculated by M06-2X and MP2 methods are almost consistent with each other.     

Syntheses and structures of nickel–tungsten μ-tellurophenyl complexes CpNi(PPh<Subscript>3</Subscript>)(μ-TePh)W(CO)<Subscript>5</Subscript> and [CpNi(PPh<Subscript>3</Subscript>)(μ-TePh)]<Subscript>2</Subscript>W(CO)<Subscript>4</Subscript>

Syntheses and molecular structures of the heterometallic complexes of nickel cyclopentadienyl triphenylphosphine tellurophenolate with tungsten carbonyls (II and III) (CIF files CCDC nos. 1559733 and 1559734, respectively) are described.     

Synthesis and spectral studies on NiS<Subscript>4</Subscript>, NiS<Subscript>2</Subscript>PN,NiS<Subscript>2</Subscript>P<Subscript>2</Subscript> chromophores: Single-crystal X-ray structure of [Ni(dbpdtc)<Subscript>2</Subscript>] (dbpdtc = benzyl(4-(benzylamino)phenyl)dithiocarbamate)

Three complexes of a dithiocarbamate ligand (dbpdtc = benzyl(4-(benzylamino)phenyl)dithiocarbamate), namely [Ni(dbpdtc)₂] (1), [Ni(dbpdtc)(NCS)(PPh₃)] (2) and [Ni(dbpdtc)(PPh₃)₂]ClO₄ (3) have been prepared. The complexes were characterized by IR, electronic spectroscopy and cyclic voltammetry. A single-crystal X-ray structural analysis was carried out for complex 1 and showed that the nickel is in a distorted square planar environment with a NiS₄ chromophore. For the two mixed ligand complexes, the thioureide ν _C–N values were shifted to higher wavenumbers compared to [Ni(dbpdtc)₂], suggesting increased strength of the thioureide bond due to the presence of the π-accepting phosphine. Electronic spectral studies suggest square planar geometries for the complexes. Cyclic voltammetry showed easier reduction of nickel(II) to nickel(I) in the mixed ligand complexes compared to [Ni(dbpdtc)₂].     

A comparative study of carbon nanotube supported MFe<Subscript>2</Subscript>O<Subscript>4</Subscript> spinels (M = Fe,Co, Mn) for amperometric determination of H<Subscript>2</Subscript>O<Subscript>2</Subscript> at neutral pH values

Three ferrites of type MFe₂O₄ (where M is bivalent Fe, Co or Mn) dispersed on multi-walled carbon nanotubes (MWCNTs) were prepared by a coprecipitation method. Their electrocatalytic properties toward the reduction of H₂O₂ at pH 7.4 were systematically compared. Catalytic reduction rates at an applied potential of ?0.4 V (vs. Ag/AgCl) and pseudo Michaelis-Menten constants show the electrocatalytic ability to follows the order Fe₃O₄ > CoFe₂O₄ > MnFe₂O₄. This diversity is attributed to the differences in the M(II) used and its occupancy on the lattice surface. The sensitivities are 120.98 ± 0.15, 48.45 ± 0.23 and 32.25 ± 0.27 μA cm^?2 mM^?1, and the limits of detection are 0.98, 2.59 and 5.64 μM of H₂O₂ (at an S/N ratio of 3).

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Graphical abstract The activity diversity of MFe₂O₄ originates from the differences of the M(II) substitution and its occupancy on the lattice surface. Moreover, a process of electrochemical sensing of H₂O₂ is illustrated.