Halochrome Molekeln. Synthese und acidobasisches Verhalten substituierter 3′,6′-Bis (dimethylamino)-spiro [5H-imidazo [2, 1-α]-isoindolin-5,9′-xanthene]

Halochromic Molecules. Synthesis and Acidobasic Behaviour of Substituted 3′,6′-Bis(dimethylamino)-spiro [5H-imidazo [2,1-α]isoindolin-5,9′-xanthenes] Substituted 3′,6′-Bis (dimethylamino)-spiro [5H-imidazo [2, 1-α]isoindolin-5,9′-xanthenes] are prepared and their ¹H-NMR. spectra are discussed. An investigation of the complex protonation equilibria is made by stopped flow kinetic and spectrophotometric methods. pK values are determined and the results are discussed.     

Silver polymolybdates and polytungstates as cathodes in lithium-organic solvent batteries

The behaviour of positive electrodes based on silver polymolybdate (Ag₂Mo₂O₇, Ag₆Mo₁₀O₃₃) and polytungstates (Ag₂W₂O₇, Ag₂W₄O₁₃) in lithium-organic solvent batteries has been investigated. The performances of the lithium/silver oxosalt couples are given and the discharge processes are discussed.     

Induction of cholesteric mesophases in nematic liquid crystals by some chiral aryl alkyl carbinols : A quantitative investigation

A series of chiral aryl alkyl carbinols, dissolved in MBBA and other nematic solvents, induce cholesteric structures. The handedness of the induced mesophases and the twisting power of the dopant alcohols are studied by means of CD and Grandjean-Cano microscopic techniques. The investigation points out the possibility of obtaining information on the stereochemistry of the dopant by studying the characteristics of the induced helices.Two different types of H- bonds between alcohols and MBBA are discussed in connection with a possible model of induction.     

Structural revision of clusianone and 7-epi-clusianone and anti-HIV activity of polyisoprenylated benzophenones

For the first time, the tautomeric pairs of clusianone and 7-epi-clusianone were isolated from the same source, Clusia torresii fruits. An extensive NMR spectroscopic study is described to establish ¹H and ¹³C chemical shift assignments and the C-7 relative configuration of these epimers and to clarify contradictory NMR spectroscopic data previously reported. Quantum mechanical computations than pointed out the relationship between indirect coupling constants and the equilibrium between the B-ring chair and twist-boat forms of the bicyclo-[3.3.1.]-nonane system. Clusianone, 7-epi-clusianone and polyisoprenylated benzophenones 18,19-dihydroxyclusianone, propolone A and nemorosone were screened for their activity against HIV infection in C8166 cells. All compounds inhibited infection with selectivity index values ranging from 2.25 to 15.6. Only clusianone derivatives inhibited infection by binding to viral protein gp120 and prevented its interaction with cellular receptor CD4 as detected by ELISA using recombinant proteins.     

Polysaccharides at interfaces 1. Adsorption of cholesteryl-pullulan derivatives at the solution-air interface. Kinetic study by surface tension measurements

The surface properties of a series of cholesteryl-pullulan (CHP) derivatives have been assessed by surface tension measurements at the solution-air interface. The results reveal that these properties are related to the nature of the hydrophobic cholesteryl group substituted in pullulan, and that the unsubstituted polysaccharide does not display any surface activity. The adsorption kinetics of such an amphiphilic macromolecule has been shown to be diffusion controlled, obeying the Ward and Tordai¨diffusional model only at low solution concentrations. In the 2 × 10⁻⁷–5 × 10⁻⁶ mol l⁻¹ concentration range for which this model is verified, the calculated diffusion coefficients are concentration dependent. The non-ideality of the system at higher concentrations may be explained both by the presence of solute/solute interactions in solution and in adsorbed monolayers, and by the existence of an adsorbed layer, even at time t₀, which prevents the process of adsorption from being governed only by diffusion.     

Structure of trans-chloro-1,4-bis(ϱ-methoxyphenyl)-1,4-diaza-3methylbutadiene-2-yl-bis(triphenylphosphine)-palladium(II)

The structure of the compound trans-[PdCl {$\text{C(N-?-C}{}_6\text{H}{}_4\text{OMe)C}$(Me)N-?-C₆H₄OMe} (PPh₃)₂] was solved, using a conventional combination of Patterson and Fourier functions, least-squares refinements and electron density difference maps, to a reliability index R of 0.069 for the 2923 observed reflections collected by four-circle diffractometer. The palladium arom is surrounded in a roughly planar fashion by two trans phosphorus atoms, a chlorine atom, and a σ-bonded carbon atom of the diazabutadienyl group. This group assumes a trans configuration, the NCCN fragment being virtually planar and nearly normal to the mean coordination plane. The Pdligand bond lengths are: PdC 1.98(1), PdCl 2.41(1),PDP(1) 2.33(1) and PdP(2) 2.35(1) Å.     

Selenium-tellurium sequences in binary glasses as depicted by 77Se and 125Te NMR

Some resolved solid state (77)Se NMR spectra are presented in the Te(x)Se(1-x) vitreous system at ambient temperature. They exhibit three different kinds of Se lines assigned to the following Se atom neighborhoods: Se-Se-Se, Se-Se-Te, and Te-Se-Te. Different models were considered to describe the way the Se and Te atoms are linked into the chains: clustering process, homogeneous distribution, random distribution. Finally, thanks to the measurements of the relative intensities of the lines, it appears that Se and Te atoms are mainly randomly distributed with a small preference for heteropolar bonds. The (125)Te spectra are also shown but their resolution is too weak to be informative concerning the vitreous network.     

Crystal and Molecular Structure of the 4:3 Complex between Lanthanum Nitrate and Pentaethyleneglycol Dimethyl Ether

The crystal and molecular structure of [La(NO₃)₃]₄(C₁₂H₂₆O₅)₃ has been determined from low-temperature single-crystal X-ray diffraction data. The complex crystallizes in the monoclinic space group I2 with Z = 2. Lattice parameters at 150 K are a = 12.234 (6) Å, b = 11.105 (5), c = 26.613 (9), β = 90.65 (4)°. The structure was solved by Patterson and Fourier techniques and refined to a conventional R_F-value of 0.068. The compound contains three dinitrato complex cations [La(NO₃)₂C₁₂H₂₆O₆]⁺ with 10-coordinate lanthanum ions and one hexanitrato anion, [La(NO₃)₆]^3?, with a 12-coordinate La(III)-ion. One complex cation has a C₂-symmetry while the two others, which are crystallographically equivalent, have no symmetry and contain a disordered ligand molecule. The polyther adopts a ring-like conformation in all the complex moietis. The La? O(nitrate) distances lie in the ranges 2.52–2.53 and 2.49–2.62 Å, with average values of 2.53 (7) and 2.56 (6) Å, respectively, fo the species with C₂- and C₁-symmetry; the La? O(ether) bond lengths lie int he range 2.54–2.79 Å (average: 2.6 (1)) for the C₂-moiety and their mean value amounts to 2.6 (2) for the disordered species. The hexanitrate has a C₂-symmetry and the La? O distances range between 2.56 and 2.67 Å with an average value fo 2.64 (4) Å. The effective ionic radii of the 10- and 12-coordinate La(III) ions are estimated as 1.28 and 1.33 Å, respectively.     

Ruthenium(II) Complex of the Alkaloid 2-Bromoleptoclinidinone. Preparation and Interaction with Double-Stranded DNA

The fused pentacyclic alkaloid 2-bromoleptoclinidinone ( 1 ) isolated from an ascidian possesses a bidentate chelating site. Complexation of 1 with [cis-RuCl₂{(D₈)bpy}₂] · 2H₂O forms an octahedral complex which was isolated both as hexafluorophosphate 2 and chloride 3 salts. Intercalation of 3 in calf-thymus DNA was shown to occur as well as photoactivated cleavage of double-strand supercoiled DNA pBR322 under visible-light irradiation.