Role of electronic and structural factors in the origin of ambergris-type odors in cyclic compounds

The relationship between the electronic structure and odorant properties of organic compounds has been investigated. The conclusion previously drawn in [1] regarding the electronic-topological features characterizing the active portion of a molecule (the ambergris triangle) has been confirmed on the basis of quantum-chemical calculations. Possibilities for designing new compounds with an ambergris-type odor have been demonstrated with the aid of the prediction system devised.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 3, pp. 355–359, May–June, 1986.     

Role of crystal chemical factors in the formation of the magnetic structure of inorganic compounds

The role of crystal chemical factors in the development of conditions for the formation of the magnetic structure of inorganic compounds is shown. A crystal chemical method is proposed to quantitatively estimate the strength of magnetic interactions and to determine magnetic moment orientation based on the structural data. By the example of determining the magnetic structures of two known antiferromagnetics Cs2CuCl4 and Sr2CuO3 the correspondence between the results obtained by this method and the experiment is shown. It is found that the search for new materials with the sought magnetic structure can be made using the data on the crystal structure of compounds. New Tl2Cu(CO3)2, BaCu2(AsO4)2, BaV2P2O10, VOSe2O5, KCu(CO3)F, and A(VO)(XO4) (A = Li, Na, NH4, K; X = P and As) magnets containing low-dimensional fragments are found. Magnetic interactions are analyzed; based on the structural data, the sign and strength of magnetic interactions is calculated both inside the low-dimensional fragments and between them; geometrical frustrations are studied in all compounds found.     

Properties of binary complex compounds

The current state of studies on binary complex compounds [M¹L _a ] _x ·[M²A _b ] _y (M¹ and M² are the central ions, L and A are ligands) is considered, notably: synthesis, composition, structures, magnetic properties, and thermal decomposition.     

Bond critical points in the electronic structures of binary hydrides

The bond critical points of the binary hydrides formed by the elements of the first two rows of the periodic table have been calculated. Particular attention has been paid to the basis-set dependence of the bond critical points at the experimental equilibrium geometries, or where necessary at model geometries. With the exception of H₂S, stepwise extension of the basis set leads to a smooth convergence of the bond critical points to a set of values which appear to converge to the Hartree–Fock limit. For H₂S it is shownb that the position of the bodn critical point is not only more sensitive to the presence of polarization functions in the basis set, but depends strongly on the orbital exponents of the polarization functions. Extensive optimizations of the exponents of the polarization functions have been carried out with the (12s9p/5s) basis set for second-row hydrides. The effects of contracting the Huzinaga basis sets have been examined.     

Couplings between electronic transitions in a subsystem formulation of time-dependent density functional theory

A subsystem formulation of time-dependent density functional theory (TDDFT) within the frozen-density embedding (FDE) framework and its practical implementation are presented, based on the formal TDDFT generalization of the FDE approach by Casida and Wesolowski [Int. J. Quantum Chem. 96, 577 (2004)]. It is shown how couplings between electronic transitions on different subsystems can be seamlessly incorporated into the formalism to overcome some of the shortcomings of the approximate TDDFT-FDE approach in use so far, which was only applicable for local subsystem excitations. In contrast to that, the approach presented here allows to include couplings between excitations on different subsystems, which become very important in aggregates composed of several similar chromophores, e.g., in biological or biomimetic light-harvesting systems. A connection to Forster- and Dexter-type excitation energy coupling expressions is established. A hybrid approach is presented and tested, in which excitation energy couplings are selectively included between different chromophore fragments, but neglected for inactive parts of the environment. It is furthermore demonstrated that the coupled TDDFT-FDE approach can cure the inability of the uncoupled FDE approach to describe induced circular dichroism in dimeric chromophores, a feature known as a "couplet," which is also related to couplings between (nearly) degenerate electronic transitions.     

Effect of the composition of zeolite paranatrolite on the configuration of its water-cation subsystem

The Rietveld method is used to determine the structure of two samples of high-hydrated zeolite paranatrolite: {Na_1.15Ca_0.38Sr_0.04(H₂O)_3.1}[Al_2.19Si_2.81O₁₀] (Vishnevye Mountains, Urals) and {Na_2.01K_0.04H_0.04(H₂O)_3.8}[Al_2.10Si_2.90O₁₀] (Kirov Mine, Khibiny Massif). Paranatrolite from the Vishnevye Mountains is characterized by the presence of split water positions and a relatively low total H₂O content. Local water-cation assemblages (WCAs) of three configurations are identified in the statistical “mixture”. The extraframework subsystem in the structure of Khibiny paranatrolite is made of WCAs of one configuration. The H₂O content of this mineral is close to the maximum possible amount and is a recordbreaker for natrolite-type minerals.     

Total energy calculations in the DFT on binary compounds

Calculations are carried out using first-principles self-consistent local-density and nonlocal density theory of the electronic structure, the total energy, and the charge density of a variety of semiconducting and insulating compounds under hydrostatic and uniaxial pressure. For several cases, the transition pressure from one structure to another is determined as well as the pressure coefficients of the main band gaps. It is shown that several properties are calculated with adequate accuracy to be compared with experiment, so that values which have not yet been measured are trustworthy predictions. © 1995 John Wiley & Sons, Inc.     

Intramolecular electronic interaction in phosphorus compounds

The intramolecular electronic interaction in a series of phosphorus compounds is considered on the basis of effects operative in these compounds: inductive, dπ-pπ conjugation, and positive charge effect.     

Thermal properties of the clathrate compounds of binary cyanides

The stoichiometry of thermal decomposition of a particular group of clathrate compounds, of the type Cd(en)Pd(CN)₄·2G, with the same coordination component but different clathrate-enclosed components, was investigated. Irrespective of the experimental conditions, the liberation of the enclosed component G always proceeded in one step. Thermal investigation of the decomposition stoichiometry under identical experimental conditions showed that the temperature intervals in which the enclosed components are given off shift to lower temperatures in the order C₆H₅OH=> C₆H₆ > > C₄H₅N > C₄H₄S. Diffraction measurements indicated a considerable change in the structures of the original clathrate compounds after thermal release of the enclosed componentG.

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Zusammenfassung Die Stöchiometrie der thermischen Zersetzung einer bestimmten Gruppe von Klathratverbindungen vom Typ Cd(en)Pd(CN)₄·2G mit der gleichen Koordinationskomponente und verschiedenen Klathrat-Einschlußkomponenten wurde in dieser Studie untersucht. Ungeachtet der Versuchsbedingungen vollzieht sich die Freisetzung der eingeschlossenen KomponenteG stets in einer Stufe. Die unter gleichen Versuchsbedingungen durchgeführte thermische Untersuchung der Zersetzungsstöchiometrie zeigte, daß die Temperaturbereiche, in denen die eingeschlossenen Komponenten freigesetzt werden in der Reihenfolge C₆H₅OH > C₆H₆ > C₄H₅N > C₄H₄S in Richtung der niedrigeren Temperaturwerte verschoben werden. Die Diffraktionsmessungen weisen darauf hin, daß eine beträchtliche Änderung der Struktur der ursprünglichen Klathratverbindung nach thermischer Freisetzung der eingeschlossenen KomponenteG sichtbar wird.

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Résumé Dans cette étude on a établi la stoechiométrie de la décomposition thermique d'un groupe particulier de clathrates du type Cd(en)Pd(CN)₄·2G, avec le même composant de coordination et différents composants occlus. Indépendamment des conditions d'expériences, la libération du composant occlusG s'effectue toujours en une étape. L'étude thermique de la stoechiométrie de la décomposition effectuée dans les mêmes conditions d'expériences, a montré que les intervalles des températures dans lesquels les composants occlus sont libérés, se déplacent vers les températures plus faibles dans l'ordre suivant: C₆H₅OH > C₆H₆ > > C₄H₅N > C₄H₄S. Les mesures de diffraction indiquent qu'après la libération thermique du composant occlusG, une variation considérable de la structure initiale des clathrates originaux apparaît.

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Cd(en)Pd(CN)₄. 2G . , G . , , , ] ₆₅>₆₆>C₄H₆N>C₄H₄S. - , G.

     

Effect of H-bond formation on the electronic spectra of some azo compounds derived from 3-amino-1,2,4-triazole

The UV-visible spectra of some azo compounds derived from 3-amino-1,2,4-triazole and various active-methylene or active-hydrogen compounds have been investigated in organic solvents of different polarities. The spectral bands obtained are assigned to the possible electronic transitions. It was found that the azo compounds containing the acetylacetone moiety exist mainly in the hydrazone form, while those containing ethylcyanoacetate, or -naphthol substituents exist in an azo hydrazone tautomeric equilibrium in solution. The extra visible band exhibited in the spectra ofo-hydroxyazo compound is assigned to an intermolecular electronic transition. The spectral shifts observed in the various organic solvents are discussed on the basis of the solute-solvent interaction through the formation of hydrogen bonds with different species. The variation of the absorbance with pH is employed to determine the acid dissociation constants.     

Controlling the formation of capillary bridges in binary liquid mixtures

We study the formation of capillary bridges between micrometer-sized glass spheres immersed in a binary liquid mixture using bright field and confocal microscopy. The bridges form upon heating due to the preferential wetting of the hydrophilic glass surface by the water-rich phase. If the system is cooled below the demixing temperature, the bridges disappear within a few seconds by intermolecular diffusion. Thus, this system offers the opportunity to switch the bridges on and off and to tune precisely the bridge volume by altering the temperature in a convenient range. We measure the bridge geometry as a function of the temperature from bright field images and calculate the cohesive force. We discuss the influence of the solvent composition on the bridge formation temperature, the strength of the capillary force, and the bridge volume growth rate. Furthermore, we find that the onset of bridge formation coincides with the water-lutidine bulk coexistence curve.     

Pattern formation in phase separating binary mixtures

We experimentally investigate the interplay of thermodynamics with hydrodynamics during phase separation of (quasi-) binary mixtures. Well defined patterns emerge while slowly crossing the cloud point curve. Depending on the material parameters of the experimental system, two distinct scenarios are observed. In quasi-binary mixtures of methanol-hexane patterns appear before macroscopic phase separation sets in. In course of time the patterns turn faint while the overall turbidity of the sample increases until the mixtures become completely turbid. We attribute this pattern formation to a latent heat induced instability resembling a Rayleigh-Bénard instability. This is confirmed by calorimetric data and an estimate of its Rayleigh number. Mixtures of C(4)E(1)-water doped with decane phase separate under heating. After passing the cloud point curve these mixtures first become homogenously turbid. While clearing up, pattern formation is observed. We attribute this type of pattern formation to an interfacial tension induced Bénard-Marangoni instability. The occurrence of the two scenarios is supported by the relevant dimensionless numbers.     

Hierarchical crystal-chemical analysis of binary intermetallic compounds

A modified Voronoi-Dirichlet polyhedra (VDP) method based on the clusterization of interatomic contacts in the crystal structure depending on contact strength is described. This method makes it possible to carry out crystal-chemical analysis hierarchically, consecutively recognizing atomic nets with different groups of interatomic contacts. The method is used to carry out the topological classification of structure representations for 547 intermetallic compounds of composition AX. Structural relations between various topologic types of intermetallic compounds are discovered and discussed.     

The 1,4-diazabutadiene/1,2-enediamido non-innocent ligand system in the formation of iridaheteroaromatic compounds: Spectroelectrochemistry and electronic structure

Oxidation of the unambiguously characterized iridium(III)-enediamido complex IrCp∗(RNCHCHNR), R = 2,6-dimethylphenyl, with six cyclically arranged π electrons was investigated using EPR and UV-vis spectroelectrochemistry. In contrast to a corresponding iminocatecholato system reported recently by Rauchfuss et al. [27] the two one-electron oxidation steps are not completely reversible, depending on the solvent. We attribute the electrochemical behavior observed in weakly coordinating dichloromethane and propylene carbonate solvents to an enhanced propensity for ligand addition: while neutral IrCp∗(RNCHCHNR) remains coordinatively unsaturated with the strongly σ and π donating enediamido(2−) ligand mitigating the electron deficit, the oxidation to the less donating radical anion ligand (RNCHCHNR)^- or even to neutral 1,4-diazabutadiene is considered to induce a strong tendency for quasi-hexacoordination in [IrCp∗(L)(RNCHCHNR)], L = solvent, halide, substrate. The presence of excess chloride thus leads to formation of the precursor complex ion [IrCp∗ClRNCHCHNR)]⁺ after oxidation. EPR spectroscopy of the one-electron oxidation intermediate [IrCp∗(RNCHCHNR)]⁺ was successful only for a frozen solution in propylene carbonate/0.1 M Bu₄NPF₆ which revealed an axial signal with sizeable g anisotropy. DFT calculation results for [IrCp∗(RNCHCHNR)]ⁿ, n = 0, +, 2+ confirm the available structural and spectroelectrochemical data (UV-vis, EPR).     

Thermodynamic properties of arsenic compounds and the heat of formation of the As atom from high level electronic structure calculations

Structures, vibrational frequencies, atomization energies at 0 K, and heats of formation at 0 and 298 K are predicted for the compounds As(2), AsH, AsH(2), AsH(3), AsF, AsF(2), and AsF(3) from frozen core coupled cluster theory calculations performed with large correlation consistent basis sets, up through augmented sextuple zeta quality. The coupled cluster calculations involved up through quadruple excitations. For As(2) and the hydrides, it was also possible to examine the impact of full configuration interaction on some of the properties. In addition, adjustments were incorporated to account for extrapolation to the frozen core complete basis set limit, core/valence correlation, scalar relativistic effects, the diagonal Born-Oppenheimer correction, and atomic spin orbit corrections. Based on our best theoretical D(0)(As(2)) and the experimental heat of formation of As(2), we propose a revised 0 K arsenic atomic heat of formation of 68.86 ± 0.8 kcal/mol. While generally good agreement was found between theory and experiment, the heat of formation of AsF(3) was an exception. Our best estimate is more than 7 kcal/mol more negative than the single available experimental value, which argues for a re-examination of that measurement.     

Adhesives and compounds in manufacture of electronic mechanisms

The general properties of adhesives and compounds for electronic articles are described that were elaborated by the company: TK-1 adhesive with elevated thermal conductivity; TEK-type adhesives that demonstrate higher elasticity and adhesion ability; TK-8-type all-purpose adhesives; MS-type, single-packed, thermally stable glues for long storage; electrically conductive adhesives; TPK-1 and TPK-2 magnetic adhesives and TPK-3 nonmagnetic adhesive; and some compounds, e.g., epoxide molding compositions. The functionality of all adhesives and compounds presented were tested for weather factors, including elevated humidity, higher and lower temperatures, thermal cycles, effects of vibrations for both pilot samples, and final articles of electronic mechanisms.