Vapor Pressure of Some Metal Phthalocyanines

The temperature dependences of saturated vapor pressures of hexadecafluorinated zinc and vanadyl phthalocyanines (MPcF₁₆, M = Zn, VO) and their unsubstituted analogues were studied by the Knudsen effusion method. The temperature dependences of saturated vapor pressures were used to calculate the thermodynamic parameters of vaporization of phthalocyanines.     

Structure of rhenium coatings obtained by CVD

By chemical vapor deposition in the hydrogen atmosphere from Re₂(CO)₁₀ and Re(CO)₃(Cp) on steel and ceramic (C/SiC) substrates, rhenium coatings are obtained with an average thickness of 3–13 μm, when Re₂(CO)₁₀ is used, and of 2–8 μm when depositing from Re(CO)₃(Cp). The coatings are studied by X-ray diffraction and scanning electron microscopy. It is shown that when Re₂(CO)₁₀ is used, an increase in the deposition temperature results in the growth of textured coatings with preferred orientation of crystallites in the [0 0 2] direction. At the same time, a tendency for decreasing the size of rhenium crystallites is observed. With the change of evaporator temperature, the structure of Re coatings obtained from Re(CO)₃(Cp) on steel substrates changes considerably: from compact non-layered without the obvious growth direction (T _evaporator = 120°C) to a three-layer structure, where the initial layer has a compact structure followed by columnar and powdered layers (T _evaporator = 110°C). A fine compact coating is formed on ceramic substrates at an evaporator temperature of 110°C.     

X-ray diffraction study of volatile complexes of dimethylgold(III) derived from symmetrical β-diketones

Crystal chemical investigation of volatile dimethylgold(III) β-diketonates of the general formula (CH₃)₂AuL [L = acetylacetone (acac), dipivalylmethane (dpm), dibenzoylmethane (dbm)] has been carried out for the first time. The synthetic procedure and structural data are reported; differential thermal analysis (DTA) data are given. The structure of the compounds includes monomeric complex molecules arranged as polymeric stack associates. The gold atom has a plane square environment AuO₂C₂ formed by two oxygen atoms of the bidentate (O,O) ligand and two methyl groups. The geometrical characteristics of the coordination units are the following: in all complexes, the Au-O and Au-C_Me bond lengths and O-Au-O chelate angles are 2.070–2.108 Å, 1.989–2.034 Å, and 89.7-93.7°, respectively. The shortest Au-Au distance (3.475 Å) in the stack is observed for the (CH₃)₂Au(dpm) complex.     

Molecular dynamics method in studies of molecular film growth processes

This review is an attempt to analyze some of the experimental problems arising in the course of growth of orientated molecular films using metal monophthalocyanine (MPc) films as an example and to demonstrate the possibilities of molecular dynamics simulation of these processes for solving experimental problems. Examples of theoretical simulation of adsorption processes are given; formation of a molecular monolayer is considered for copper phthalocyanine films as an example.     

Synthesis and crystal structure determination of iridium(III) acetylacetonate and its Br-and I-substituted analogs

γ-Halogen-substituted iridium(III) acetylacetonates of general formula Ir(acacX)₃,where acacX = CH₃ -CO-CX-CO- CH₃,X =Br, I, were synthesized. The compounds are characterized by melting points and chemical analysis data for C, H, Br, and I. An X-ray diffraction analysis was performed for iridium(III) acetylacetonate and its y-substituted analogs, crystal data were obtained, and crystal structures were determined. The crystals are monoclinic;the structures are molecular. Crystal data: Ir(acac)3 _- IrO₆C₁₅H₂₁,a = 13.900(2), b = 16.440(3), c = 7.494(2) å, γ =98.63(2)?, V= 1693.2 å³,space group P2₁/b,Z = 4, d_calc =1.92 g/cm³,sin θ/λ_max = 0.703, F_hkl = 2841, R = 0.044. Ir(acacBr)_3- IrBr₃O₆C₁₅H₁₈,a = 12.794(2), b = 15.753(2), c = 9.990(2) å Β = 105.76(2)?, V= 1937.6 å³,space group P2₁/n,Z =4, d_calc =2.49 g/cm³, sinθ/λ_max = 0.702, F_hkl = 1748, R = 0.048. Ir(acacI)3- M₃O₆C₁₅H₁₈,a = 12.855(2), b = 10.136(2), c =16.338(3)å, Β = 104.6(2)?, V=2059.8å³,space group P2₁/n, Z =4, d_calc = 2.79g/cm³, θ_max =25?, F_hkl = 2817, R =0.032. The Ir..Ir distances were estimated to be > 7.49 å for Ir(acac)3 and > 8.10 å for Ir(acacBr)3 and Ir(acacl)₃.If the estimate is limited to 10 å, the intermolecular coordination number (ICN) in the structures is 10.     

Study of test structures of a molecular memory element

Electrophysical parameters of a molecular memory element were measured. It was established that it has an S-shaped voltage-current characteristic with memory. Information recording/erasure parameters were measured. For some elements, 10 nsec recording times with an information storage time of 1.5 months were obtained. The number of recording/erasure cycles exceeded 10⁸. A conclusion is drawn that the design of storage devices based on a molecular memory element is promising.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 6, pp. 152–156, November–December, 1993.Translated by L. Chernomorskaya     

Mass spectrometric study of the thermal decomposition mechanism of vapors of 2,2,6,6-tetramethyl-3-iminoheptane-5-one and its copper(II) complex

Thermal conversions of vapors of ketoimine C(CH₃)₃C(NH)CH₂C(O)C(CH₃)₃ (Htmha = 2,2,6,6-tetramethyl-3-iminoheptane-5-one) and its chelate coordination compound with copper Cu(tmha)₂ is studied by in situ mass spectrometry in a vacuum and in the presence of hydrogen. Experiments are carried out under conditions close to low pressure chemical vapor deposition at the evaporator temperature of 130 °C and the reactor temperature range 130-500 °C. It is found that compounds are monomeric in the gas phase. Based on temperature dependences of the composition of primary gaseous products, the mechanism of thermal decomposition is proposed. The decomposition of ketoimine on the heated surface begins at 350 ± 10 °C and proceeds by the elimination of terminal groups. Its copper complex decomposes in two directions and yields both molecular and radical products. The latter provide the assumption that metallic copper forms as the only one solid product. The results obtained are compared with those for copper dipivaloylmethanate(2,2,6,6-tetramethylheptane-3,5-dionate).     

Structural Study of Ni(dpm)2 in Solution by X-Ray Absorption Spectroscopy

The NiK-absorption spectra of Ni(dpm)₂ and its adducts in crystal and solution have been studied. X-ray spectra were recorded on a synchrotron radiation station of the Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. It is shown that the fundamental absorption maximum in the compounds is of Rydberg character. The fine structure of the fundamental maximum was used for structure elucidation of the nearest environment of the metal atom of the complex in solutions and adducts. Participation of the highest unoccupied AO of the metal in chemical bonding in the compounds is discussed.     

Vapor pressure and crystal structure of platinum(II) <Emphasis Type="Italic">trans</Emphasis>-bis-(trifluoroketoiminate)

The temperature dependence of the saturated vapor pressure of the trans-Pt(ktf)₂ complex obtained from fluorinated β-ketoimine (CF₃-CO-CH₂-C(NH)-CH₃) was studied by the flow method. The standard thermodynamic parameters ΔH ₀ ^T and ΔS ₀ ^T of sublimation have been determined. Full crystal-chemical study has been performed for the complex. Crystal data for C₁₀H₁₀F₆N₂O₂Pt: a = 5.9790(8) Å, b = 7.373(2) Å, c = 8.5767(2) Å,α = 84.05(2)°, β = 72.43(1)°, γ = 67.14(1)°, V = 332.1(1) ų, Z = 1, d_calc = 2.496 g/cm³, triclinic, space group \(P\bar 1\). The structure is molecular and consists of isolated trans-Pt(ktf)₂ complexes. The Pt atom lies at the symmetry center and has a square planar environment of two oxygen and two nitrogen atoms; the distances Pt-O (1.984 Å) and Pt-N (1.969 Å) are similar within the limits of 2σ; the OPtN bond angle is 93.9°. Molecular packing in crystal is considered based on structural data; van der Waals energy of the crystal lattice of trans-Pt(ktf)₂ was calculated by the atom-atom potential method.     

Parameters and Form of the Mössbauer Spectra of Iron(III) β-Diketonates: New Data

Mössbauer spectra have been measured at 295 and 78 K for ten ⁵⁷Fe-enriched iron(III) -diketonates differing in the type of radical in the chelate ring. Since the literature data for compounds of this class are incomplete and contradictory, a repeated analysis of spectrum shape and parameters has been performed. The chemical shift and quadrupole splitting are virtually independent of the type of radical in the chelate ring whereas the line width and asymmetry exhibit a pronounced dependence on the temperature and composition of the compounds. The available concepts on the nature of quadrupole splitting and relaxation mechanisms determining the lineshape for the given compounds are refined. It is concluded that electron spin relaxation is longitudinal or transverse relative to the principal axis of the electric field gradient in different compounds.