Phlogophites intercalated with Al2O3 pillars and modified with transition metals as catalysts of the DeNOx process

Natural phlogophite, pre-treated with acids and intercalated with alumina pillars, was used as catalytic support. Transition metals (Fe, Cu) were deposited on the surface of the modified clay materials by an ion-exchange method. The obtained samples were characterized with respect to structure (XRD), texture (BET), composition (EPMA) and chemical nature of the deposited transition metals species (UV-vis-DRS). The phlogophite based materials have been found to be active and selective catalysts of the DeNOx process. The Fe-containing samples were catalytically active at lower temperatures than the clays modified with copper. A competitive ammonia oxidation by oxygen decreased the effectiveness of the DeNOx process in the high temperature range.     

Note on a theoretical interpretation of the isotopic ratio vOH/vOD versus vOH in isotopically diluted HDO molecules in solid hydrates

A simple intra- and inter-molecular potential for water molecules engaged in hydrogen bonding has been used in a one-dimensional approximation for a theoretical interpretation of the experimental correlation $\text{v}$_OH/$\text{v}$_OD versus $\text{v}$_OH in solid hydrates. The variation in the equilibrium OH(D) distance has also been considered.     

Photophysics of aromatic molecules with low-lying pi sigma* states: excitation-energy dependence of fluorescence in jet-cooled aromatic nitriles

Excitation-energy dependence of fluorescence intensity and fluorescence lifetime has been measured for 4-dimethylaminobenzonitrile (DMABN), 4-aminobenzonitrile (ABN), 4-diisopropylaminobenzonitrile (DIABN), and 1-naphthonitrile (NN) in a supersonic free jet. In all cases, the fluorescence yield decreases rather dramatically, whereas the fluorescence lifetime decreases only moderately for S1 (pi pi*, L(b)) excess vibrational energy exceeding about 1000 cm(-1). This is confirmed by comparison of the normalized fluorescence excitation spectrum with the absorption spectrum of the compound in the vapor phase. The result indicates that the strong decrease in the relative fluorescence yield at higher energies is due mostly to a decrease in the radiative decay rate of the emitting state. Comparison of the experimental results with the TDDFT potential energy curves for excited states strongly suggests that the decrease in the radiative decay rate of the aminobenzonitriles at higher energies is due to the crossing of the pi pi* singlet state by the lower-lying pi sigma*(C[triple bond]N) singlet state of very small radiative decay rate. The threshold energy for the fluorescence "break-off" is in good agreement with the computed energy barrier for the pi pi*/pi sigma* crossing. For NN, on the other hand, the observed decrease is in fluorescence yield at higher excitation energies can best be attributed to the crossing of the pi pi* singlet state by the pi sigma* triplet state.     

Square-Planar Nickel(II) O,O′-Dialkyldithiophosphato Complexes with Triphenylphosphine of the Type [NiX(S2P{OR}2)(PPh3)] (X = Cl,Br, I and NCS)

A series of new [NiX(S₂P{O-c-Hex}₂)(PPh₃)](X = Cl^–, Br^–, I^– and NCS^–)(1)–(4) and [Ni(NCS)(S₂P{OR}₂)(PPh₃)][R =n-Pr (5), i-Pr (6)] complexes has been synthesized and characterized by elemental analyses, f.i.r., i.r., u.v.–vis., ¹H-, ¹³C{¹H}- and ³¹P{¹H}-n.m.r. spectra, magnetochemical and conductivity measurements. A single crystal X-ray analysis of [Ni(NCS)(S₂P{O-n-Pr}₂)(PPh₃)](5) reveals the molecular structure of the complex and confirms a square-planar geometry around the central atom of nickel with the NCS anion coordinated via the nitrogen atom.     

Solvatochromic equilibria of cobalt(II) chloride in binary mixtures of dipolar aprotic solvents with water

The visible absorption spectra of CoCl₂ in binary mixtures of acetone, dmf, dma and dmso with H₂O show the existence of configuration equilibria between tetrahedral (T) and octahedral (O) species. Linear correlations between the values of log K (K = [O]/[T]) and the mole fraction of H₂O, _w, have been observed in all the systems under study; their slopes decrease linearly with an increase of the donor number, DN, of the organic component of the mixture. The formation of octahedral species is enthalpy favoured but entropy disfavoured. It was found that both H and S values change linearly with _w and the slopes of these relationships depend clearly on the DN values.     

The electronic absorption study of imide anion radicals in terms of time dependent density functional theory

The absorption spectra of the N-(2,5-di-tert-butylphenyl) phthalimide (1-), N-(2,5-di-tert-butylphenyl)-1,8-naphthalimide (2-) and N-(2,5-di-tert-butylphenyl)-perylene-3,4-dicarboximide (3-) anion radicals are studied in terms of time dependent density functional theory (TDDFT). For these anion radicals a large number electronic states (from 30 to 60) was found in the visible and near-IR regions (5000-45,000 cm(-1)). In these regions the TD/B3LYP treatment at the 6-1+G* level is shown to reproduce satisfactorily the empirical absorption spectra of all three anion radicals studied. The most apparent discrepancies between purely electronic theory and the experiment could be found in the excitation region corresponding to D0-->D1 transitions in the 2- and 3- molecules. For these species we argue that the structures seen in the lowest energy part of the absorptions of the 2- and 3- species are very likely due to Franck-Condon (FC) activity of the totally symmetric vibrations not studied in this Letter.     

Coordination compounds of nickel with trithiocyanuric acid. Part IV. Structure of [Ni(pmdien)(ttcH)] (pmdien = N,N,N′,N′,N′′-pentamethyldiethylenetriamine,ttcH3 = trithiocyanuric acid)

Ni^II mixed-ligand complexes of compositions [Ni(pmdien)(ttcH)] (1), [Ni(baphen)₂(ttcH)] · 4H₂O (2), [Ni-(dpa)(ttcH)(H₂O)] (3), [Ni(cyclam)(ttcH)] · 2H₂O (4), [Ni(hexaa)](ttcH) (5) and [Ni(hexab)(ttcH)] · 2H₂O (6), (baphen = 4,7-diphenyl-1,10-phenanthroline, dpa = 2,2-dipyridylamine, cyclam = 1,4,8,11-tetraazacyclotetradecane, hexaa = 1,3,6,9,11,14-hexaazatricyclo[12.2.1.1^6,9]-octadecane, hexab = 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane) have been prepared and characterized by means of i.r., u.v.–vis. spectroscopies and magnetochemical measurements. The redox properties of the complexes were studied by cyclic voltammetry. The crystal and molecular structure of [Ni(pmdien)(ttcH)] was determined. The nickel atom is penta-coordinated by three N atoms of pmdien, and by S and N atoms of trithiocyanurate(2–) anion.     

EDS X-Ray Investigation of Interdiffusion in Au–Ni Micro- and Nanolayers

The interdiffusion process in thin and thick (500nm–60µm) Au–Ni layers deposited on different substrates is studied using the EDS technique. In-depth X-ray analysis based on the Pouchou and Pichoir method is applied for obtaining the concentration profiles in nanometre scale multi-layers. A theoretical analysis using the Darken method is employed for modelling interdiffusion in the Au–Ni system. Computer simulations, where intrinsic diffusivities of the Au and Ni are functions of composition, are presented and compared with experimental results.