SCF non-additivity of the interaction energy in the neon trimer

The three-body non-additivity of the interaction energy for the equilateral triangle configuration of the Ne₃ system has been calculated, using the counterpoise method within the SCF approach. The induction-type non-additivity has been estimated and compared with the first-order exchange one.     

On nd bonding in the transition metal trimers: comparison of Sc3 and Y3

CASSCF/CCI calculations are presented for the low-lying states of Y₃. Comparison of the wave functions for Y₃ and Sc₃ indicates substantial 4d-5p hybridization in Y₃, but little 3d-4p hybridization in Sc₃. The increased 4d-5p hybridization leads to stabilization of 4d bonding with respect to 4d bonding for equilateral triangle Y₃, and also leads to 4d-5p bonding for linear geometries. These effects lead to a different ordering of states for equilateral triangle geometries and a smaller excitation energy to the linear configuration for Y₃ as compared to Sc₃.     

The structure and magnetic properties of μ3-oxotriiron(III) complex [Fe3O(OBz)6(CH3OH)3](NO3)(CH3OH)2

A new μ₃-O triiron(III) complex [Fe₃O(OBz)₆(CH₃OH)₃](NO₃)(CH₃OH)₂ (HOBZ = benzoic acid) has been synthesized, its structure has been determined and variable temperature magnetic susceptility has also been measured. In the molecule, three iron atoms formed an equilateral triangle with μ₃-O in center. The fitting to the magnetic susceptibility showed that an intramolecular antiferromagnetic exchange interaction occurred between iron atoms with J=-25.51 cm^?1, and a weaker intermolecular autiferromagnetic exchange interaction occurred with zJ' = ?2.30 cm^?1.     

Ab initio copper–water interaction potential for the simulation of aqueous solutions

A new ab initio effective two-body potential that aims at mimicking the average copper–water interaction energy of the first solvation shell was developed. This new potential, together with the MCY water–water potential and a three-body ion–water–water induction potential, is tested in simulations of gas-phase clusters [Cu²⁺? (H₂O)₂₀] and diluted solutions [Cu²⁺? (H₂O)₂₀₀] at T = 298 K. The results of simulations with conventional ab initio pair potentials, with and without three-body induction corrections, are also presented. The different types of copper–water interaction potentials are evaluated comparatively and the efficiency of the newly proposed effective pair potential is discussed. © 1993 John Wiley & Sons, Inc.     

On the Controversial Fitting of Susceptibility Curves of Ferromagnetic CuII Cubanes: Insights from Theoretical Calculations

This paper reports a theoretical analysis of the electronic structure and magnetic properties of a tetranuclear Cu^II complex, [Cu₄(HL)₄], which has a 4+2 cubane‐like structure (H₃L=N,N′‐(2‐hydroxypropane‐1,3‐diyl)bis(acetylacetoneimine)). These theoretical calculations indicate a quintet (S=2) ground state; the energy‐level distribution of the magnetic states confirm Heisenberg behaviour and correspond to an S₄ spin–spin interaction model. The dominant interaction is the ferromagnetic coupling between the pseudo‐dimeric units (J₁=22.2 cm^?1), whilst a weak and ferromagnetic interaction is found within the pseudo‐dimeric units (J₂=1.4 cm^?1). The amplitude and sign of these interactions are consistent with the structure and arrangement of the magnetic Cu 3d orbitals; they accurately simulate the thermal dependence of magnetic susceptibility, but do not agree with the reported J values (J₁=38.4 cm^?1, J₂=?18.0 cm^?1) that result from the experimental fitting. This result is not an isolated case; many other polynuclear systems, in particular 4+2 Cu^II cubanes, have been reported in which the fitted magnetic terms are not consistent with the geometrical features of the system. In this context, theoretical evaluation can be considered as a valuable tool in the interpretation of the macroscopic behaviour, thus providing clues for a rational and directed design of new materials with specific properties.     

Isotopically resolved {ie30-01} electronic spectrum of Ag3 and calculation of its Jahn-Teller effects

Ag₃ was produced by pulsed-nozzle laser vaporisation and jet-cooled in a Ne supersonic expansion. Onecolor resonant two-photon ionisation (R2PI) spectra of the {ie30-02} transition of Ag₃ were separately measured for all four isotopic combinations. Long vibrational progressions are observed, involving clearly resolved bands at low energy, merging into a dense but resolvable spectrum up to 1000 cm¹ above the origin. Both the ground {ie30-03} and excited {ie30-04} states of Ag3 are susceptible to Jahn-Teller distortion along the degenerate e′ bending coordinate. The Jahn-Teller analysis includes both linear and quadratic terms, simultaneously with the spin-orbit coupling. Following extensive parameter fitting, the absorption spectrum is calculated, and bands assigned. The spin-orbit splitting is quenched below the localization energy, but becomes observable ≈ 300 cm^-1 above the origin.     

Nature of interaction energy anisotropy in the Li(<Superscript>2</Superscript>S)–HF (˜X<Superscript>1</Superscript>Σ<Superscript>+</Superscript>) van der Waals complex. A theoretical study

The potential-energy surface for the Li(²S)–HF (? X¹Σ⁺ interaction, where HF is kept rigid, is calculated using the supermolecular unrestricted fourth-order Møller–Plesset perturbation theory. The basis set superposition error corrected potential indicates two minima. The global minimum occurs for the bent Li...FH structure at R=1.95 Å and θ=70° with a relatively deep well of D_e=1,706 cm^?1 and the secondary minimum is found for the linear Li...HF configuration at R=4.11 Å with a well depth ofD_e=288 cm^?1. A barrier of 177 cm^?1 (with respect to the secondary linear minimum) separates these two minima. In this study 27 bound states of the bent Li...FH minimum and eight bound states of the linear Li...HF minimum up to the Li+HF dissociation threshold are calculated. The energy partitioning using the intermolecular perturbation theory scheme shows that the origins of the stability of the structures studied are entirely different. The global minimum is stabilised using the attractive Coulombic interaction and unrestricted Hartree–Fock deformation energy. The latter term originates from the mutual electric polarisation effects. The secondary linear minimum is mostly determined by the anisotropy of the repulsive Heitler–London exchange-penetration and attractive dispersion energies.     

Darstellung und Charakterisierung von Phthalocyanin-π-Kation-Radikalen von H+, Mg2+ und Cu2+

Preparation und Characterization of Phthalocyanine-π-Cation-Radicals of H⁺, Mg²⁺, and Cu²⁺ The preparation of phthalocyanine-π-cation-radicals (Pc(?1)) of H⁺, Mg²⁺, Cu²⁺ is described. MgClPc(?1) and Cu(NO₃)Pc(?1) · HNO₃ are isolated as stoichiometrically pure, stable redbrown solids. Contrary to the phthalocyanines(?2) (Pc(?2)) these are very soluble with redviolet colour in organic solvents in the presence of R? COOH (R ? H, CF₃, CCl₃). The electronic absorption absorption spectra (UV-VIS) are remarkably solvent-dependent. This solvent effect is due to a reversible radical association. Monomeric radical species exist in nonpolar (CH₂Cl₂), dimeric in polar solvents (CH₃NO₂, C₂H₅OH). The UV-VIS, infrared (IR), and resonance-raman (RR) spectra of MgClPc(?1) and Cu(NO₃)Pc(?1) · HNO₃ are discussed and compared with the analogoues spectra of MgPc(?2) · 2 H₂O and MgPc(?2) · HCl. Although there are only minor differences in the chemical composition and the electronic structure the spectroscopic data vary significantly for every complex. Especially the IR spectrum is suitable for a quick demonstration of the π-cation-radicals. The diagnostic bands are at ca. 1350 and 1450 cm^?1.     

Ab initio determination of the ground-state potential energy curve for Ar2

A totally ab initio potential energy curve for Ar₂ is constructed by adding individually damped dispersion terms to an accurate single configuration self-consistent-field repulsive interaction curve. However, the well depth (77 cm^?1) of our computed curve is significantly less than the experimentaly deduced value (99.4 cm^?1)     

EPR of dynamic Jahn-Teller distortion in CuII doped magnesium Tutton's salt

The dynamic Jahn-Teller distortion in single crystals of Cu^II doped magnesium Tutton's salt, MgK₂(SO₄)₂·6H₂O was studied by EPR spectroscopy. The directions of the g tensor axes were found to coincide with those of A at room temperature as well as at 113 K and were correlated with the MgO directions in the lattice. Two spatially distinct sites of copper were detected in the crystal. The g and A values were also calculated from the polycrystalline samples at various temperatures. A d_x²-_y² ground state has been assigned for Cu^II, as in the isomorphous zinc Tutton's salt. The Silver and Getz model was applied to understand the dynamics of Jahn-Teller (JT) activity. The system was found to undergo dynamic JT distortion at all temperatures. At low temperatures, the [Cu(H₂O)₆]²⁺ ion has three possible degenerate vibronic states corresponding to three possible directions for the long axis of the octahedron. The energy separations between the three inequivalent JT valleys were estimated as δ_1,2 = 90 and δ_1,3 = 370 cm⁻¹. The lattice strain parameter V₂ and the JT stabilization energy E_JT were also estimated as 19,140 and 1030 cm⁻¹ respectively. From the E_JT value, the JT distortion present in the system was classified as a case of “strong” coupling.     

Metal Complexes with Macrocyclic Ligands. Part XLVI. Synthesis and structures of dinuclear metal complexes of bis-macrocycles having a pyrazole bridging unit

Three bis-macrocyclic ligands consisting of two N₃-, N₂S-, or NS₂-cyclononane rings, i.e., of two octahydro-1H-1,4,7-triazonine, octahydro-1,4,7-thiadiazonine, or hexahydro-5H-1,4-7-dithiazonine rings, connected by a 1H-pyrazolediyl unit were prepared. They form dinuclear Cu^II and Ni^II complexes which are able to bind one additional exogenous bridging molecule such as Cl^?, Br^?, N, SO, and 1H-pyrazol-1-ide. The structures determined by X-ray diffraction show that each Cu²⁺ is coordinated by the three donor atoms of the macrocyclic ring, by a pyrazolidodiyl N-atom, by an atom of the exogenous bridging ligand, and sometimes by a solvent molecule. In the majority of the Cu²⁺ cases, the metal ion exhibits square-pyramidal or trigonal-bipyramidal coordination geometry, except in the sulfato-bridged complex, in which one Cu²⁺ is hexacoordinated with the participation of a water molecule. The X-ray structure of the azide-bridged dinuclear Ni²⁺ complex was also solved and shows that both Ni²⁺ centres have octahedral coordination geometries. In all complexes, the 1H-pyrazolediyl group connecting the macrocycles is deprotonated and bridges the two metal centres, which, depending on the exogenous ligand, have distances between 3.6 and 4.5 Å. In the dinuclear Cu²⁺ complexes, antiferromagnetic coupling is present. The azido-bridged complex shows a very strong interaction with ?2J ≥ 1040 cm^?1; in contrast, the H-pyrazol-1-ide and chloride bridged species have ?2J values of 300 and 272cm^?1, respectively. Cyclic voltammetry of the Cu²⁺ complexes in MeCN reveals a strong dependence of the potentials Cu^II/Cu-^II → Cu^II/Cu^I → Cu^I/Cu^I on the nature of the donor atoms of the macrocycle as well as on the type of bridging molecule. The more S-donors are present in the macrocycle, the higher is the potential, indicating a stabilization of the Cu¹ oxidation state.     

A relativistic C.I. study on theJ=1/2 even spectrum of Sr II

We present a method for performing relativistic CI calculations in ground and excited atomic and ionic levels. An electron occupying a relativistic shellnκ in a given electronic configuration is described by a single numerical four-component Dirac-Fock orbital having the samen and κ quantum numbers to those of the shellnκ. Application of this method yields estimates for the I.P. (88 741 cm^?1) and the core correlation energy (?30916 cm^?1) for Sr II and for the total correlation energy in Sr III (?30916 cm^?1). Core-valence correlation energies for the |core 5s〉 (?4379 cm^?1), |core 6s〉 (?1191 cm^?1) and |core 13s〉 (?32 cm^?1) levels have been calculated for Sr II. Estimates for the total relativistic, Breit, vacuum polarization and self energy corrections for these levels are also reported. Configurations in which the core is not fully occupied have been found to yield significant contributions to the correlation energies of both ground and excited levels. Our results show that full scale relativistic CI calculations using numerical four-component Dirac-Fock orbitals are feasible and provide a useful ab-initio tool for the investigation of atomic properties within the framework of fully relativistic theories.     

3-body energy terms in a quartet state of H3

Calculations of the 3-body energy term in a quartet (⁴A₂) state of H₃ (equilateral triangle nuclear-configurations) show a minimum in the 3-body energy for a side length of about 1.3 bohrs.     

Copper(II) trinuclear complex with trimesic acid salicylidene hydrazone: Synthesis,structure, and magnetic properties

A trinuclear copper(II) complex of trimesic acid salicylidene hydrazone (H₆L) having the composition [Cu₃L · 4Py] · CH₃OH was synthesized and characterized. By X-ray crystallography, the crystals are triclinic: a = 11.7940(4) Å, b = 13.7241(5) Å, c = 15.8993(6) Å, α = 107.4120(10)°, β = 94.2900(10)°, γ = 105.5650(10)°, space group \(P\bar 1\), Z = 2. The number of symmetrically unique reflections having I > 2σ(I) is 7636, R = 0.0465, and R _w = 0.1198. The newly prepared complex contains, in its unit cell, two [Cu₃L · 4Py] molecules which are linked to form a dimer on account of phenoxo bridges (the Cu-O bond length is 2.555 the Cu…Cu distance is 3.348 Separations between them are 9.414, 9.371, and 9.667 of temperature is satisfactorily fitted in terms of a triangular cluster model (?2J = 2.2 cm^?1) with extra intermolecular interactions (zJ′ = 0.4 cm^?1). EPR spectra of solutions at 360–380 K feature a poorly resolved HFS, whose modeling gives a satisfactory result with allowance for the interaction of unpaired electrons with three equivalent copper nuclei (g = 2.098; a _Cu = 25.8 × 10^?4 cm^?1).     

A Dual‐Ligand Porous Coordination Polymer Chemiresistor with Modulated Conductivity and Porosity

Single‐ligand‐based electronically conductive porous coordination polymers/metal–organic frameworks (EC‐PCPs/MOFs) fail to meet the requirements of numerous electronic applications owing to their limited tunability in terms of both conductivity and topology. In this study, a new 2D π‐conjugated EC‐MOF containing copper units with mixed trigonal ligands was developed: Cu₃(HHTP)(THQ) (HHTP=2,3,6,7,10,11‐hexahydrotriphenylene, THQ=tetrahydroxy‐1,4‐quinone). The modulated conductivity (σ≈2.53×10^?5 S cm^?1 with an activation energy of 0.30 eV) and high porosity (ca. 441.2 m² g^?1) of the Cu₃(HHTP)(THQ) semiconductive nanowires provided an appropriate resistance baseline and highly accessible areas for the development of an excellent chemiresistive gas sensor.     

Reaction of the unsaturated anion [Re3H4(CO)10]− with mercaptans. Synthesis and X-ray Characterization of the anion [ Re3H3 (CO)9(μ3-SBut)]−

The novel anion [Re₃H₃(CO)₉(μ₃-SBu^t)]^?, obtained by reaction of [Re₃H₄(CO)₁₀]^? with t-butyl mercaptan, has been characterized by IR, NMR and X-ray diffraction studies. It contains an equilateral Re₃ triangle (mean ReRe 3.091 Å), with nine terminal carbonyl groups, three for each metal atom, and a triply-bridging thiolate ligand (mean ReS 2.393 Å). The three hydrides are bridging on the edges of the triangle of metal atoms.     

Ultraviolet absorption spectra of some alkylchloramines

The ultraviolet spectra of six alkylchloramines are determined between 220 and 320 nm. The wavelengths of maximum absorption are 244 nm (? = 458 l mol^?1 cm^?1) for monochloramine, 252 nm (? = 372 l mol^?1 cm^?1) for methylchloramine, 251 nm (? = 378 l mol^?1 cm^?1) for ethylchloramine, 250 nm (? = 368 l mol^?1 cm^?1) for isopropylchloramine, 264 nm (? = 354 l mol^?1 cm^?1) for dimethylchloramine and 262 nm (? = 315 l mol^?1 cm^?1) for diethylchloramine.     

EPR studies on pairs of Jahn-Teller distorted hexakis pyridine-N-oxide ions in Zn(C5H5NO)6(NO3)2

Semi-dilute 10% ⁶³Cu:Zn(pyO)₆(NO₃)₂ (pyO = C₅H₅NO, pyridine-N-oxide) has been studied by X- and Q-band EPR. Below the transition from dynamic to static Jahn-Teller distortion, various pairs of Cu(pyO)²⁺₆ ions are observed, including the antiferrodistortive one with the largest possible exchange interaction, which pair was not present in the corresponding ClO^?₄ crystal. From the AB type of spectrum which is observed at Q-band, the weak exchange interaction in antiferro-distortive pairs was determined: J′ = 329 10^?4 cm^?1, larger than the corresponding values in the ClO^?₄ and BF^?₄ complexes.     

Interaction of zinc oxide clusters with molecules related to the sulfur vulcanization of polyolefins ("rubber")

The vulcanization of rubber by sulfur is a large‐scale industrial process that is only poorly understood, especially the role of zinc oxide, which is added as an activator. We used the highly symmetrical cluster Zn₄O₄ (T_d) as a model species to study the thermodynamics of the initial interaction of various vulcanization‐related molecules with ZnO by DFT methods, mostly at the B3LYP/6‐31+G* level. The interaction energy of Lewis bases with Zn₄O₄ increases in the following order: CO62H₄3H₆2S₂<1,4‐C₅H₈2O2S3N?CH₃COO^?. The corresponding binding energies range from ?57 to ?262 kJ mol^?1. However, Brønsted acids react with the Zn₄O₄ cluster with proton transfer from the ligand molecule to one of the oxygen atoms of Zn₄O₄, and these reactions are all strongly exothermic [binding energies [kJ mol^?1] in parentheses: H₂O (?183), MeOH (?171), H₂S (?245), MeSH (?230), C₃H₆ (?121), and CH₃COOH (?255)]. The important vulcanization accelerator mercaptobenzothiazole (C₇H₅NS₂, MBT) containing several donor sites reacts with the Zn₄O₄ cluster with proton transfer from the NH group to one of the oxygen atoms of ZnO, and in addition the exocyclic thiono sulfur atom and the nitrogen atom coordinate to one and the same zinc atom, resulting in a binding energy of ?247 kJ mol^?1. A second isomer of [(MBT)Zn₄O₄] with a strong O? H???N hydrogen bond rather than a Zn? N bond is only slightly less stable (binding energy ?243 kJ mol^?1). The NH form of free MBT is 36 kJ mol^?1 more stable than the tautomeric SH form, while the sulfurized MBT derivative benzothiazolyl hydrodisulfide C₇H₅NS₃ (BtSSH) is most stable with the connectivity >CSSH.     

Studies on the magnetic property of μ3-oxotriiron(III) complex [Fe3O(OBz)6(CH3OH)3](NO3)(CH3OH)2 (HOBz?Benzoic acid)

The magnetic property of μ₃-oxotriiron(III) complex [Fe₃O(OBz)₆(CH₃OH)₃](NP₃)-(CH₃OH)₂ (HOBz? benzoic acid) has been studied. We use isosceles triangle model and molecular field correction to fit the experimental magnetic susceptibility data. It shows that an intramolecular antiferromagnetic exchange interaction occurs with J = -31.27 cm^?1, J'= -27.26 cm^?1, and a weaker intermolecular antiferromagnetic exchange interaction occurs with zJ' = - 3.76 cm^?1. We give the d⁵-d⁵-d⁵ energy level diagram of triiron(III) complex as a function of J'/J. From the diagram we can get the total spin ST of the complex as 1/2 in the ground state.