Intramolecular excimer of DI(1-pyrenylmethyleneoxycarbonyl) alkanes

Intramolecular excimer emission of a series of di(1-pyrenylmethyleneoxycarbonyl)alkanes (n = 0–22) has been studied under photostationary conditions. The intramolecular excimer formation rate constant decreases monotonously with increasing number of methylene units of the chains in the low temperature region. The temperature dependence of the rate constant for each sample was studied to give an apparent activation energy of ca. 5 kcal/mol.     

Intramolecular excimer formation in macromolecules—V. Head-to-head polystyrene,block copolymers of styrene and butadiene and regular condensation polymers of α-methylstyrene

Studies of the photophysical properties of head-to-head polystyrene, block copolymers poly(butadiene-b-styrene) and polystyrenes of various sequence length of styrene chromophore and regular copolymers of α-methylstyrene indicate that interactions between phenyl chromophores located distantly upon the macromolecule are not of major significance in determination of excimer formation in styrene polymers. It is concluded that intramolecular excimer formation in polystyrenes occurs primarily as a consequence of interactions between nearest neighbour chromophores in the polymer chain. The influence of polymer coil dimensions upon intramolecular excimer formation is demonstrated. The photophysical behaviour of poly(butadiene-b-styrene) block copolymers shows the importance of intramolecular energy migration in population of potential excimer sites.     

Some aspects of the dependence of solid-state structure on electron count

The method of moments is used to show how the structures of molecules and solids is sensitive to the number of valence electrons.     

Temperature dependence of fluorescence and phosphorescence from probe molecules in polymer substrates

The effect of temperature on the fluorescence and phosphorescence from a series of indole and coumaric acid derivatives incorporated in poly(methyl methacrylate), poly(styrene) and poly(vinyl alcohol) substrates has been investigated in the range 90–300 K. Activation energies for the temperature-dependent non-radiative decay of the triplet excited states showed abrupt changes at temperatures corresponding to the onset of local relaxation processes in the polymers. The values of activation energies and transition temperatures in any one polymer did not depend greatly on the probe, suggesting that the temperature-dependent triplet state deactivation mechanisms are mainly influenced by extrinsic polymer properties. However, the effect of temperature on the fluorescence intensity was found to depend markedly on the probe and state of ionization of any one probe. Possible explanations for these observations are presented.     

Intramolecular disorder and its relation to mesophase structure in lyotropic liquid crystals

NMR SPDE measurements are reported for the lamellar (dispersions and multibilayer stacks) and hexagonal phases of sodium octanoate/octanol/D₂O mixtures. In the lamellar L_β and L_γ (gel) phases the octyl chains are rigid and perfectly ordered, while in the lamellar L_α and hexagonal phases they are flexible and disordered. In particular, the measurements show that in the fluid lamellar L_α phase, there is a marked discontinuity in the octyl chain flexibility at the C₅-C₆ segment; this behaviour is identical to that previously reported for the alkyl end-chains in smectic 4,4′-di-n-octyloxyazoxybenzene. In contrast, in the hexagonal phase, there is an effectively continuous flexibility gradient along the whole length of the octyl chain as in nematic 4,4′-di-n-octyloxyazoxybenzene. The behaviour in the lamellar phase is attributed to interference between cooperative conformational modes and localized random thermal fluctuations.     

Thermal decomposition kinetics of p-toluenesulphonamide and some of its n-halogeno and n-metal derivatives

The TG, DTG and DTA traces of p-toluene sulphonamide, chloramine-T, dichloramine-T, dibromamine-T and the Ag and Hg derivatives of p-toluene sulphonamide are given and interpreted. The kinetic parameters (energies and entropies of activation and pre-exponential factors) for the main decomposition stages have been calculated.     

The capacity versus potential dependence of the electrical double layer of the mercury/electrolyte solution of the dicarboxylic ions

The effect of dicarboxylic ions on the capacity hump was investigated by measuring the double layer capacity of the mercury/water electrolyte solution interface. Further experimental evidence was found of the internal rotation effect of the molecule in the double layer electric field. When discussing the effect of dicarboxylic ions on the capacity hump, it is assumed that the latter is due not only to dipole-ion, dipole-electrode and electrode-ion interactions but moreover occurs as the result of intra-ionic electrostatic interaction and the ability of the ion/or its fragment/to reorient in the electric field of the interface.     

Trivalent phosphorus derivatives of group via : IV. Infrared and pmr studies of the protonation of M(CO)6−n(PA3)n Complexes (M = Mo,W; A = CH3, OCH3; n = 2, 3, 4)

The action of trifluoroacetic acid on the series M(CO)_6?n(PA₃)_n (M = Mo, W; A = CH₃, OCH₃; n = 2, 3, 4) has shown that protonation occurs if n ? 3. For n = 3 the basicity of the ligand PA₃ plays a more important role in the stability of [HM(CO)₃(PA₃)₃]⁺complexes than for n = 4. Infrared and proton NMR give evidence of the stereochemical non-rigidity of the [HM(CO)_6?n(PA₃)_n]⁺ heptacoordinated cation.     

Crystal growth and electrical properties of lithium,rubidium, and cesium molybdenum oxide bronzes

Crystals of Li_0.33 MoO₃ (blue), Rb_0.23MoO₃ (blue) and Cs_0.31MoO₃ (red) were grown by electrolysis from MoO₃M₂MoO₄ melts (M =alkali metal) with composition 70–77 mole% MoO₃. Melts richer in M₂MoO₄ produced MoO₂ only. Correlation is made between bronze formation and the coordination of Mo in the melt and in the equilibrium solid phase M₂Mo₄O₁₃. Li_0.33MoO₃ and Cs_0.31MoO₃ are semiconductors with high-temperature-range activation energies 0.16 and 0.12 eV. Rb_0.23MoO₃ has an electrical behavior similar to that of blue K_xMoO₃ with a semiconductor-metal transition at (170 ± 5) K. ESR spectra observed in Li_0.33MoO₃ and Rb_0.23MoO₃ single crystals at 4.2 K show extensive delocalization of the 4d¹ electron associated with Mo(V) centers. Attempts to grow molybdenum bronzes containing Ca or Y were unsuccessful.     

Intramolecular exciplex laser

Laser action of the intramolecular exciplex emission of p-(9′-anthryl)-N,N-dimethylaniline (ADMA) has been found in non-polar and slightly polar solvents. In moderately as well as strongly polar solvents, the laser emission is quenched in spite of the fact that the spontaneous fluorescence yields is larger in polar than in non-polar solvents.     

Interaction of chloroform with aniline, o-toluidine and N,N-dimethyl aniline

Heats of mixing aniline, o-toluidine, and N,N-dimethyl aniline with chloroform have been determined by an adiabatic calorimeter. The results have been examined for molecular interactions between them, and they indicate that aniline and o-toluidine are associated through hydrogen bonds. Enthalpy of bond formation in a 1:1 complex has also been determined.     

Ln(Fe3+M2+)O4 compounds with layer structure [Ln : Y,Er, Tm,Yb, and Lu, M : Mg,Mn, Co,Cu, and Zn]

A series of new compounds Ln(Fe³⁺M²⁺)O₄ [Ln : Y, Er, Tm, Yb, and Lu, M : Mg, Mn, Co, Cu, and Zn] were successfully synthesized and their lattice constants were determined. These compounds have the same crystal structure as YbFe₂O₄ and Fe³⁺ and M²⁺ are both surrounded by five oxygen ions forming a trigonal bipyramid. The synthetic conditions are presented. They are strongly dependent upon the constituent cations of the compound.     

Thermodynamic functions of gaseous beryllium,titanium and germanium organometallic molecules

The thermal functions S⁰_T, -(G⁰_T-H⁰_O)/T and (H⁰_T-H⁰_O) have been calculated from structural and spectroscopic data for the gaseous organometallics C₅H₅BeX (X = Cl, Br and BH₄), C₅H₅MX₃ (M = Ti and Ge; X = Cl, Br and I) and CH₃TiX₃ (X = Cl, Br and I). The rotational barriers of the C₅H₅ and CH₃ groups have been evaluated and discussed.     

Atomic-absorption spectrophotometric determination of antimony, arsenic, bismuth, tellurium, thallium and vanadium in sewage sludge

Electrothermal atomic-absorption spectrophotometry (AAS), by use of a graphite furnace, in conjunction with sample pretreatment by homogenization, was evaluated as a rapid method for the determination of bismuth, thallium and vanadium in sewage sludge. This method was compared with use of flame, electrothermal and hydride-generation (for bismuth) AAS in conjunction with conventional acid digestion and dry-ashing pretreatments and was found to be applicable to this type of sample. Comparisons were also made between flame and hydride-generation AAS in conjunction with an acid digestion pretreatment for the determination of antimony, arsenic and tellurium in sewage sludge. The hydride-generation technique was considered the better for waste-water samples because of its greater sensitivity.     

Direct potentiometric titration of thiosulfate,thiourea, and ascorbic acid with lodate using an iodide ion-selective electrode

A potentiometric method has been developed for the semi-automatic direct titration of thiourea, thiosulfate, and ascorbic acid with potassium iodate in strongly acidic solutions using an iodide ion-selective electrode to monitor the reaction and locate the endpoint. The method is simple, fast, precise, and accurate. Amounts ranging from 0.15–1.5 mg of thiourea (3.9 × 10^?4–3.9 × 10^?3, M), 0.3–3.0 mg of thiosulfate (5.4 × 10^?4–5.4 × 10^?3, M), and 0.5–5.0 mg of ascorbic acid (5.7 × 10^?4–5.7 × 10^?3, M) have been determined with an average error of about 1%. The method has been applied to the determination of ascorbic acid in tablets. Results checked closely with those obtained with a standard titrimetric method.     

The preparation,properties, crystal lattice and thermal decomposition reactions of cobalt malonate dihydrate

Cobalt malonate dihydrate crystallizes in the monoclinic system, the dimensions of the unit cell are reported. On heating, two molecules of water are lost at ～400 K to give the anhydrous salt which is amorphous to X-rays. At higher temperatures (520K) the initial stages of carboxylate decomposition obey the zero-order kinetic equation to 30% reaction. Thereafter, there is a marked diminution in rate of the vacuum reaction but kinetic behaviour is sensitive to the gases present; the influences of reaction products, of carbon monoxide and of oxygen have been investigated quantitatively. Form these observations we conclude that the decomposition of cobalt malonate proceeds by an autocatalytic mechanism, through the nucleation and growth of an ill-crystallized mixture of product phases. The rate of reactions at the reactant-product contact surface are controlled, to some extent, by available gaseous molecules which may participate in equilibria at the interface and at active surfaces of the residual phases.     

Interaction of cyclopentane with benzene,carbon tetrachloride and cyclohexane

Heats of mixing cyclopentane + benzene, + carbon tetrachloride, + cyclohexane at 308.15 K and for cyclohexane + carbon tetrachloride at 298.15 K have been determined in an adiabatic calorimeter. The data have been examined for current theories (McGlashan, Flory and Barker) of solutions and show that McGlashan's theory predicts values for H^E and G^E that are in good agreement with their corresponding experimental values. Interaction energy between the components of these mixtures has also been determined.     

Structural characterization of Fe/Ti oxide photocatalysts by X-ray,ESR, and Mössbauer methods

The polycrystalline solids TiO₂Fe₂O₃, with iron contents in the range 0–10 at.%, prepared by coprecipitation and by impregnation, and treated in air at temperatures in the range 500–1000°C, have been studied by X-ray, ESR, and Mössbauer methods. The TiO₂ in the samples treated at 800 and 1000°C always forms the rutile phase and the Fe³⁺ has a rather low solubility in it (～0.1 at.%). The Fe³⁺ in excess forms the antiferromagnetic pseudobrookite phase (Fe₂TiO₅). The samples treated at 500 and 650°C show a dependence on the preparation method. Those prepared by coprecipitation give at 500°C the pure anatase phase in which the Fe³⁺ has a higher solubility (≥ 1%); those prepared by impregnation give the anatase phase accompanied by a variable amount of rutile. The treatment at 650°C provokes the partial transformation of anatase to rutile and the complete development of the Fe₂TiO₅ phase. The relevance of these results to the photocatalytic properties shown by these solids for the photoreduction of dinitrogen to ammonia is discussed.     

Spinel, YbFe2O4, and Yb2Fe3O7 types of structures for compounds in the In2O3 and Sc2O3---A2O3---BO systems [A: Fe, Ga, or Al; B: Mg, Mn, Fe, Ni, Cu, or Zn] at temperatures over 1000°C

In the Sc₂O₃---Ga₂O₃---CuO, Sc₂O₃---Ga₂O₃---ZnO, and Sc₂O₃---Al₂O₃---CuO systems, ScGaCuO₄, ScGaZnO₄, and ScAlCuO₄ with the YbFe₂O₄-type structure and Sc₂Ga₂CuO₇ with the Yb₂Fe₃O₇-type structure were obtained. In the In₂O₃---A₂O₃---BO systems (A: Fe, Ga, or Al; B: Mg, Mn, Fe, Ni, or Zn), InGaFeO₄, InGaNiO₄, and InFe³⁺MgO₄ with the spinel structure, InGaZnO₄, InGaMgO₄, and InAlCuO₄ with the YbFe₂O₄-type structure, and In₂Ga₂MnO₇ and In₂Ga₂ZnO₇ with the Yb₂Fe₃O₇-type structure were obtained. InGaMnO₄ and InFe₂O₄ had both the YbFe₂O₄-type and spinel-type structures. The revised classification for the crystal structures of AB₂O₄ compounds is presented, based upon the coordination numbers of constituent A and B cations.