Magnetic Anisotropy of Small Ir<Subscript>n</Subscript> Clusters (n = 2–5)

We employ a noncollinear implementation of density functional theory (DFT) including spin–orbit coupling (SOC) interaction to calculate the magnetic properties of Ir_n (n = 2–5) clusters. The impact of the magnetic anisotropy on the geometric structures and magnetic properties has been analyzed. SOC leads to formation of large orbital moment and a mixing of different spin states, but does not affect the relative stability of different structural isomers for a given cluster. In order to measure the SOC effect, we further define the spin–orbit energy (E_so) and compute the exact values. Magnetic anisotropy energies (MAEs) obtained from DFT calculations are further supported by the results of torque approach. We find that MAEs of Ir₂ and Ir₃ in ground state configurations are 40.6 and 28.5 meV respectively, while the MAE decreases to 9 meV for Ir₄. For Ir₅, MAE for its ground state structure increases to 38.3 meV.     

Hydrogen abstraction reactions of OH radicals with CF<Subscript>2</Subscript>ClCClXH (X = F,Cl) and CFCl<Subscript>2</Subscript>CClXH (X = F,Cl): a mechanistic and kinetic study

The reactions of OH (OD) radicals with CF₂ClCClFH (R1), CF₂ClCCl₂H (R2), CFCl₂CClFH (R3), and CFCl₂CCl₂H (R4) have been investigated theoretically by a dual-level direct dynamics method. The optimized geometries and frequencies of the stationary points are calculated at the MPW1K/6-311+G(d,p) level. To improve the reaction enthalpy and potential barrier of each reaction channel, the single-point energy calculation is made by the MC-QCISD method. The enthalpies of formation of the species CF₂ClCClFH, CF₂ClCCl₂H, CFCl₂CClFH, CFCl₂CCl₂H, CF₂ClCClF, CF₂ClCCl₂, CFCl₂CClF, and CFCl₂CCl₂ are evaluated by two sets of isodesmic reactions. Using canonical variational transition state theory (CVT) with the small-curvature tunneling correction (SCT) method, the rate constants of OH and OD radicals with CF₂ClCClXH (X = F, Cl) and CFCl₂CClXH (X = F, Cl) are evaluated over a wide temperature range of 100–2,000 K at the MC-QCISD//MPW1K/6-311+G(d,p) level. The calculated CVT/SCT rate constants are consistent with available experimental data. The results show that the tunneling correction has an important contribution in the calculation of rate constants at lower temperatures. For the above-mentioned four reactions, the kinetic isotope effects are also calculated. Finally, the effect of fluorine or chlorine substitution on reactivity of the C–H bond is discussed.     

Stabilities of Al<Subscript>n</Subscript>Cu (n = 1–19) Clusters and Magnetic Properties of Three Cu-Doped Al Clusters

By using the Amsterdam Density Functional program, we have studied the geometric features, stabilities and magnetic properties of Al_nCu (n = 1–19) clusters. The magnetic structures of Al₁₇Cu₂ and Al₁₉Cu clusters are found. Although the high spin ground state of Al₁₂Cu cluster is in accordance with the Hund’s rule under spherical Jellium model (SJM), it is difficult to explain why the Al₁₇Cu₂ and Al₁₉Cu clusters exhibit larger magnetic moments by the model. A superatom model under equivalent charge distribution is proposed. The magnetic properties of the Cu-doped Al clusters can be explained well by combination of the superatom model with SJM.     

Effect of P-Containing Ligands on the Structural and Optical Properties of (CdSe)<Subscript>n</Subscript> (n = 3, 6, 10) Clusters

The effect of phosphorus-containing ligands on the structure, energetics and properties of the (CdSe)_n clusters (n = 3, 6, and 10) with different number of PH₃ and PMe₃ ligands were studied by using density functional theory calculations. The P atom in the ligand interacts with Cd and forms a strong Cd–P coordination bond. The introduction of ligands does not change the cluster architecture, but leads to considerable changes in Cd–Se bondlength, charge distribution, binding energy, HOMO–LUMO gap and optical absorption. The ligand influence is enhanced with increasing ligand coverage. A blueshift in absorption band was predicted for the clusters with increasing ligands, resulting from the electron donating characteristics of the ligands that hamper electron transition from Se to Cd. As P-containing ligands are often used in the preparation of CdSe nanocrystals, our calculations reveal the influence of ligand-cluster interaction on the cluster geometrical and electronic properties, which would be helpful for the nanocrystal design and synthesis.     

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.     

Investigation of Zn<Subscript>m</Subscript>Cd<Subscript>n</Subscript>X<Subscript>y</Subscript> (y = m + n; X = Te,Se and S) Clusters with TDDFT Method

Based on zinc blende and wurtzite structures of experimental ZnTe and CdTe nanocrystals, Zn_mCd_nX_y (X = Te, Se and S) clusters were investigated using DFT/B3LYP/LANL2DZ. From analyses of their characters of conformations, HOMO–LUMO gaps, Raman and absorption spectra, Mulliken charges and WBI (Wiberg Bond Index) values, we have discovered that Zn_mCd_nTe_y, Zn_mCd_nSe_y and Zn_mCd_nS_y molecules had similar characters. In this paper, characters of Zn_mCd_nTe_y were investigated in detail. First, we have found that HOMO–LUMO gaps, Raman spectra, absorption spectra, bond lengths and Mulliken charges of doping Zn₂CdTe₃, ZnCd₂Te₃, Zn₃CdTe₄, Zn₂Cd₂Te₄ and ZnCd₃Te₄ structures were in the scope of corresponding naked ZnTe and CdTe clusters. These characters of doping Zn_mCd_nTe_y molecules show that their stabilities are good. Second, comparing with ZnTe structures, the wavelengths of the absorption peaks of doping Zn_mCd_nTe_y clusters shift to red in water environment. Moreover, with increasing of the number of Cd atom, their wavelengths of the absorption peaks gradually shift to red. This conclusion is consistent with the experimental fact. Third, Raman spectra of pure ZnTe clusters have higher frequencies than corresponding naked CdTe structures. As for doping molecules, the frequencies of their Raman spectra gradually shift to low frequencies with increasing of Cd atoms’ number.     

Exploring the Reactivity of Rh<Subscript>2</Subscript> (OAc)<Subscript>4</Subscript> with 2, 2′ -Dipyridylamine

A series of three new compounds obtained from the reaction of Rh₂(OAc)₄ and 2, 2 -dipyridylamine (Hdpa) under various conditions have been characterized. All are diamagnetic and have a Rh–Rh single bond. In Rh₂(dpa)₄, 1, there are four bridging dpa anions which bind the two Rh atoms through one pyridyl N atom and one amido N atom though two of these ligands interact further with a rhodium atom through the third N atom. In the other two compounds the Hdpa ligand is neutral. Thus Rh₂(OAc)₄(Hdpa)₂, 2, is an adduct of the well known complex dirhodium tetraacetate in which the two Hdpa ligands occupy axial positions. In the third compound, Rh₂(Hdpa)₂(OAc)₂Cl₂, 3, only two acetate bridges are present. One Hdpa molecule chelates equatorially each rhodium atom and the chloride ions are axially coordinated. The Rh–Rh distances are 2. 4005(6) and 2. 4042(8) Å for 1 and 2, respectively. For 3, the Rh–Rh distance of 2. 593(1) Å is significantly longer than those in 1 and 2 because of the presence of fewer bridging ligands.     

Theoretical studies of the structures and properties of (Br<Subscript>2</Subscript>InN<Subscript>3</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 1–6) clusters

In an attempt to find single-source precursors, a series of small clusters of inorganic azides of indium (Br₂InN₃) _n (n = 1–6) were studied using the dispersion correction density functional theory (wB97XD). The obtained (Br₂InN₃) _n (n = 2–6) clusters have the core structures of 2n-membered ring with alternating indium and α-nitrogen atoms. The influences of cluster size (oligomerization degree n) on the structures, energies, IR spectra, and thermodynamic properties of clusters were discussed. The computed binding energies indicate the stability: 3A > 3B, 4B > 4C > 4A > 4D, 5E > 5D > 5B = 5C > 5A and 6I > 6C > 6D > 6G ≥ 6H > 6F > 6E > 6B > 6A. It is also found that (Br₂InN₃)₂ and (Br₂InN₃)₄ clusters possess higher stability than their neighbor sizes judged by the calculated second-order difference of energies (Δ₂ E). Meanwhile, thermodynamic properties for (Br₂InN₃) _n (n = 1–6) clusters increase with the increasing temperature and oligomerization degree n, and the oligomerizations are thermodynamically favorable at temperatures up to 800 K.     

Synthesis,characterization and biological analysis of the complex [VO(Hdhp)<Subscript>2</Subscript>] (H<Subscript>2</Subscript>dhp = 2,3-dihydroxypyridine)

A new vanadium (IV) complex with the monoanion of 2,3-dihydroxypyridine (H₂dhp), or 3-hydroxy-2-(1H)-pyridone, was synthesized, characterized by physicochemical techniques and tested biologically. The EPR data for the [VO(Hdhp)₂] complex in DMF are: g _x = 1.9768, g _y = 1.9768 and g _z = 1.9390; A values (10⁻⁴ cm⁻¹): A _x , 59.4; A _y//, 59.4; A _z , 171.0. The νV=O band in the IR spectrum of the complex is at 986 cm⁻¹. The complex is paramagnetic, with μ_eff = 1.65 BM (d¹, spin-only) at 25 °C. The irreversible oxidation process [V(V)/V(IV)] of the [VO(Hdhp)₂] complex, as revealed in a cyclic voltammogram, occurs at 876 mV. The calculated molecular structure of [VO(Hdhp)₂] shows the vanadium(IV) center in a distorted square pyramidal environment, with the oxo ligand in the apical position and the oxygen donor atoms of the Hdhp ligands in the basal positions. The ability of [VO(Hdhp)₂] to mimic insulin, and its toxicity to hepato-biliary functions, were investigated in streptozotocin-induced diabetic rats and it was concluded that the length of treatment and the amount of [VO(Hdhp)₂] administered were effective in reducing experimental diabetes.     

Structural,Relative Stable,and Electronic Properties of Pb<Subscript>n</Subscript>Sn<Subscript>n</Subscript> (n = 2–12) Clusters were Investigated Using Density Functional Theory

The structural, relative stable and electronic properties of Pb_nSn_n (n = 2–12) alloy clusters were systematically studied using density functional theory. The isomers of Pb_nSn_n alloy clusters were generated and determined by ab initio molecular dynamics. By comparing the calculated parameters of Pb₂ dimer and Sn₂ dimers with the parameters from experiments, our calculations are reasonable. With the lowest-energy structures for Pb_nSn_n clusters, the average binding energies, fragmentation energies, second- order energy differences, vertical ionization potentials, vertical electron affinities, HOMO–LUMO gaps, and density of states were calculated and analyzed. The results indicate that the Sn atoms have a tendency to bond together, the average binding energies tend to be stable up to n = 8, Pb₈Sn₈ cluster is a good candidate to calculate the molecular interaction energy parameter in Wilson equation, the clusters become less chemical stable and show an insulator-to-metallic transition, 3, 6, 8 and 11 are magic numbers of Pb_nSn_n (n = 2–12) clusters, the charges always transfer from Sn atoms to Pb atoms in Pb_nSn_n clusters except for Pb₁₀Sn₁₀ cluster, and density of states of Pb_nSn_n clusters becoming continuous and shifting toward negative with the increasing size n.     

Study on the Geometric and Electronic Structures of Al<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>Si<Subscript><Emphasis Type="Italic">m</Emphasis></Subscript> (n = 3, 4, 5; m = 1, 2, 3, 4) Clusters

Genetic algorithm combined with the semi-empirical Hamitonian AM1/PM3 is used to search the low energy isomers of Al _n Si _m (n = 3, 5, m ≤ 3 and n = 4, m ≤ 4) and the charged clusters with 20 and 28 valence electrons. The candidate structures were optimized by the density functional theory PBE0 and B3LYP models with the triply split basis sets including polarization functions. The electronic structures show that Al–Si binary clusters behave like metal clusters. The molecular orbitals accord with that predicted by the jellium model, and the electron localization function shows the valence electrons are delocalized over the entire clusters. The clusters having 20 and 28 valence electrons exhibit pronounced stabilities and large energy gaps. The 20 valence electrons of Al₄Si₂ and Al₃Si₃ ⁺, Al₅Si^? form closed shells 1S ²1P ⁶2S ²1D ¹⁰. Al₄Si₄ and Al₅Si₃ ^? have oblate structures and the P, D, F levels spilt considerably in these clusters. The electron density distributions suggest that doping silicon in the aluminum clusters enhances the stability considerably.     

Theoretical Study of the Structures,Properties and Spectroscopies on Fullerene Hydrides C<Subscript>26</Subscript>H<Subscript><Emphasis Type=Italic>n</Emphasis></Subscript> (<Emphasis Type=Italic>n</Emphasis> = 2, 4, 6, 8)

The structures, stability patterns of C₂₆H _n (n = 2) formed from the initial D _3h C₂₆ fullerene were investigated by use of second-order-Moller–Plesset perturbation theory. The study of the stability patterns of hydrogenation reaction on C₂₆ cage revealed that type (β) carbons were the active site and the analyses of π-orbital axis vector indicated that the reactivity of C₂₆ was the result of the high strain and the hydrogenation reaction on C₂₆ cage was highly exothermic. The calculated ¹³C NMR spectra of C₂₆H _n (n = 2) predicted that the two sp ³ hybridization carbons in C₂₆H _n (n = 2) obviously moved to high field compare with that in D _3h C₂₆. Hence, the C₂₆H₂ should be obtained and detected experimentally. Similarly, the structures and reaction energies of C₂₆H _n (n = 4, 6, 8) were further studied at HF/6-31G*, B3LPY/6-31G* and MP2/6-31G* level. The results suggested the hydrogenation products of C₂₆, C₂₆H _n (n = 4, 6, 8), were more stable than the C₂₆ cage.     

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.     

Capping [H<Subscript>8−n</Subscript>Ni<Subscript>42</Subscript>C<Subscript>8</Subscript>(CO)<Subscript>44</Subscript>]<Superscript>n−</Superscript> (n = 6, 7, 8) Octa-carbide Carbonyl Nanoclusters with [Ni(CO)] and [CuCl] Fragments

The reactions of [Ni₁₆(C₂)₂(CO)₂₃]^4? and [Ni₃₈C₆(CO)₄₂]^6? with CuCl afforded mixtures of the previously reported [HNi₄₂C₈(CO)₄₄(CuCl)]^7? bimetallic octa-carbide cluster and the new [HNi₄₃C₈(CO)₄₅]^7? and [HNi₄₄C₈(CO)₄₆]^7? homo-metallic octa-carbides. The three species have very similar properties resulting always in co-crystals such as [NMe₄]₇[HNi_42+2xC₈(CO)_44+2x(CuCl)_1?x]·6.5MeCN (x = 0.14) (86% [HNi₄₂C₈(CO)₄₄(CuCl)]^7?, 14%[HNi₄₃C₈(CO)₄₅]^7?/[HNi₄₄C₈(CO)₄₆]^7?) and [NMe₄]₇[HNi_42+2xC₈(CO)_44+2x(CuCl)_1?x]·5.5MeCN (x = 0.30) (70% [HNi₄₂C₈(CO)₄₄(CuCl)]^7?, 30% [HNi₄₃C₈(CO)₄₅]^7?/[HNi₄₄C₈(CO)₄₆]^7?). The new homo-metallic octa-carbides can be obtained free from the Ni–Cu octa-carbido cluster by reacting [Ni₁₀(C₂)(CO)₁₆]^2? in thf with a stoichiometric amount of CuCl, and crystals of [NMe₄]₆[H₂Ni_43+xC₈(CO)_45+x]·6MeCN (x = 0.72), which contain [H₂Ni₄₄C₈(CO)₄₆]^6? (72%) and [H₂Ni₄₃C₈(CO)₄₅]^6? (28%), have been obtained. Despite the different charges and compositions, these anions display almost identical structures, which are also closely related to those previously reported for the bimetallic Ni–Cd octa-carbido clusters [Ni_42+xC₈(CO)_44+x(CdCl)]^7? and [HNi_42+xC₈(CO)_44+x(CdBr)]^6?. Indeed, all these clusters are based on the same Ni₄₂C₈ cage decorated by miscellaneous [CdX]⁺ (X = Cl, Br), [CuCl] and [Ni(CO)] fragments.     

Density Functional Study on Structure and Bonding Nature of CO Adsorbed Rh<Stack><Subscript>n</Subscript><Superscript>+/−</Superscript></Stack> (n = 2–8) Clusters

Systematic investigations on lowest energy CO adsorbed neutral and ionic Rh_n (n = 2–8) clusters in the gas phase are performed with all electron relativistic method using density functional theory within the generalized gradient approximation. Geometrical and electronic parameters are evaluated to understand the bonding nature as well as the binding interaction of CO on stable neutral and ionic rhodium clusters. Anionic adducts exhibit higher adsorption energy along with smaller Rh–C and larger C–O bond distances in comparison to neutral and cationic Rh_nCO (n = 2–8) clusters. Synergic bond formation is noticed between rhodium and carbon atom of CO molecule due to back-donation of electron from metal d-orbitals to π* orbital of CO in the case of anionic and some neutral clusters. Angular and Mülliken charge analysis along with electron density distribution suggest that anionic rhodium clusters form strong bond with carbon atom of CO than the neutral and cationic clusters.     

Reactions of 2,2′-Pyridyl with the cadmium(II) compounds: Synthesis,crystal structure,and luminescence properties of [Cd(Pic)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>] · H<Subscript>2</Subscript>O

The reactions of 2,2'-pyridyl, (2-Py)C(O)C(O)(2-Py), with the Cd(II) compounds under various conditions are studied. The medium and nature of the anions exert a decisive effect on the compositions and structures of the formed cadmium complexes. The reaction of cadmium diacetate with 2,2'-pyridyl in an aqueous-alcohol medium in air affords coordination compound [Cd(Рic)₂(H₂O)₂] · H₂O (I) (Pic^? is picolinate ion, CO₂C₅H₄N), and its crystal structure is determined. The crystals are monoclinic: space group P2₁/c, a = 7.499(1), b = 15.676(1), с = 12.719(1) Å, β = 94.79(1)°, V = 1490.0(2) Å3, Z = 4, ρ_calcd = 1.502 g/cm³. The molecular packing of compound I is a supramolecular 3D framework consisting of discrete complexes [Cd(Pic)₂(H₂O)₂] linked by hydrogen bonds O–H…O. The coordination sphere of Cd²⁺ contains two O atoms and two N atoms of the ligand and two water molecules. The coordination polyhedron of Cd²⁺ is a distorted octahedron.     

The character of interactions of CO,H<Subscript>2</Subscript>, and CH<Subscript>3</Subscript>OH with the surface of γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Cu-Zn oxide catalyst

The thermal desorption of CO, H₂, and CH₃OH from the surface of Katalco-58 industrial catalyst for the synthesis of methanol and γ-Al₂O₃ was studied. Weak interaction of the gases with the surface of samples was observed over the temperature range 75–400°C. The desorption of the gases obeyed the second-order Wigner-Polyani equation. The desorption energies of the gases were calculated. The mechanism of dimethyl ether synthesis was studied.     

Formation of oxysulfide LnO<Subscript>2</Subscript>S<Subscript>2</Subscript> and oxysulfate LnO<Subscript>2</Subscript>SO<Subscript>4</Subscript> phases in the thermal decomposition process of lanthanide sulfonates (Ln = La,Sm)

This study investigates two lanthanide compounds (La³⁺ and Sm³⁺) obtained in water/ethyl alcohol solutions employing the anionic surfactant diphenyl-4-amine sulfonate (DAS) as ligand. Both sulfonates were characterized through IR, TG/DTG (O₂ and N₂). The thermal treatment of both compounds at 1273 K under air leaves residues containing variable percentages of lanthanide oxysulfide/oxysulfate phases shown by synchrotron high-resolution XRD pattern including the Rietveld analysis. The phase distributions found in the residues evidence the differences in the relative stability of the precursors.     

Synthesis and structure of the [Co(NioxH)<Subscript>2</Subscript>(Thio)<Subscript>2</Subscript>]<Subscript>2</Subscript>SO<Subscript>4</Subscript>·2H<Subscript>2</Subscript>O complex compound

A new Co(III) complex of 1,2-cyclohexanedionedioxime and thiocarbamide with an SO ₄ ^2? anion and solvation water molecules in the outer sphere has been synthesized and its structure has been defined. Orthorhombic crystals, a = 11.659(2) Å, b = 26.448(5) Å, c = 30.142(6) Å, V = 9295(3) Å ³, Z = 8, d_calc = 1.599 g/cm³, space group Pbca; final R index is 0.0578 for 8221 reflections with I > 2σ(I). In the octahedral Co(III) complex, two 1,2-cyclohexanedionedioxime residues lie in the equatorial plane, while two thiocarbamide molecules are in the axial plane. Intramolecular bonds: N-H…O and O-H…O type hydrogen bonds and π-π interactions that stabilize the complex cations. In crystal, the components are linked by N-H…O and O-H…O hydrogen bonds into a 3D framework.