Counteranion-controlled water cluster recognition in a protonated octaamino cryptand

Structural aspects of binding of water cluster and halides in the octaamino cryptand L (1,4,11,14,17,24,29,36-octaazapentacyclo[12.12.12.2.(6,9)2.(19,22)2(31,34)]tetratetraconta-6(43),7,9(44),19(41),20,22(42),31(39),32,34(40)-nonaene, N(CH2CH2NHCH2-p-xylyl-CH2NHCH2CH2)3N) in a protonated state were examined. Crystallographic results show binding of the acyclic quasiplanar water tetramer [H4L(H2O)4](I)4.2.57H2O (1) in a tetraprotonated cryptand L having an iodide counteranion, where two water molecules reside inside the two tren-based cavity, bridged by a third water molecule, and a fourth external water molecule is hydrogen bonded to the bridged water molecule. In the case of complexes [H6L(Br)][(Br)6H].4H2O.2HBr (2) and [H6L(Cl)][(Cl)6H].10.86H2O (3), a single bromide and chloride occupied, respectively, the inside of the cryptand cavity, where L is in a hexaprotonated state. Monotopic recognition of bromide/chloride was observed at the center of the cryptand cavity where halides show C-H...halide interactions instead of the N-H...halide interactions reported in the ditopic complexes of halides with the same cryptand, 5 and 6. Thermal analyses on 1-3 were carried out, and the data obtained distinctly differentiate water cluster complex 1 from the anion-encapsulated cryptates 2 and 3. This study represents the first example of anion-controlled cluster formation inside the cavity of a cryptand.     

Organobismuth compounds : V. Preparation,characterization, and properties of triphenylbismuth diazide and dicyanide

Triphenylbismuth diazide and the dicyanide have been prepared and characterized. Previously reported triphenylbismuth hydroxide cyanide has been shown to be triphenylbismuth dicyanide. A trigonal bipyramidal structure is indicated for both the compounds on the basis of their infrared and laser Raman spectra. The molecular weight and conductance data for the diazide in acetone are also in accord with a molecular structure. The dicyanide is, however, decomposed in solution into diphenylbismuth cyanide and benzonitrile. Thermal decomposition of the solid dicyanide and the diazide has also been studied. The possibility of the conversion of the diazide and the dicyanide into the corresponding dicyanate has been explored. Unlike transition metal azides, the triphenylbismuth diazide does not react with CO. Triphenylbismuth dicyanide could also not be converted into the corresponding dicyanate by reaction with either HgO or MnO₂. Reaction with HgO afforded triphenylbismuth oxide and the reaction with MnO₂ gave uncharacterized products.     

Semiempirical molecular orbital studies on the electronic structure of molecules in excited states: The INDO/2-VN— 1 potential model: Part I.

The performance of the V_N—1 potential model at the INDO/2 level of approximation in the calculation of transition energy, singlet—triplet splitting, change in molecular structure, inversion barrier and electron-density distribution in the excited electronic states of a few simple carbonyls is analysed. The method turns out to be reasonably successful in many ways.     

On the development of exponential ansatze for quantum dynamics in finite dimensional vector spaces

Summary A Wei-Norman type of exponential ansatz is constructed for the time evolution operator in finite dimensional vector spaces. Based on an analysis of the structure of the concerned operator algebra, it is shown that a reduction principle exists even for simple algebras that goes beyond the Wei-Norman result when a specific ordering of the operators is used such that the equations of motion for different generators belonging to different classes are decoupled. It is shown that the solution in this case is global. Some specific approximation schemes are considered and their strengths and weaknesses are analyzed. Model calculations are presented to bring out these features.     

A theoretical study of the fine and hyperfine interactions in the NCO and CNO radicals

The geometries, the harmonic vibrational frequencies, and the Renner-Teller parameter have been reported for the NCO(+)(X (3)Sigma(-)), NCO(X (2)Pi,A (2)Sigma(+),B (2)Pi,2 (2)Sigma(+)), NCO(-)(X (1)Sigma(+)), CNO(+)(X), CNO(X (2)Pi,A (2)Sigma(+),B (2)Pi,2 (2)Sigma(+)), and CNO(-)(X (1)Sigma(+)) systems at the full valence-complete active space self-consistent-field (fv-CASSCF) level of theory. The (2)Pi electronic states of the NCO and CNO radicals have two distinct real vibrational frequencies for the bending modes and these states are subject to the type A Renner-Teller effect. The total energy of CNO(+) without zero point energy correction of the linear geometry is approximately 31 cm(-1) higher than the bent geometry at the fv-CASSCF level and the inversion barrier vanishes after the zero point energy correction; therefore, the ground state of the CNO(+) may possess a quasilinear geometry. The spin-orbit coupling constants estimated using atomic mean field Hamiltonian at the fv-CASSCF level of theory are in better agreement with the experimental values. The excitation energies, the electron affinity, and the ionization potential have been computed at the complete active space second order perturbation theory (CASPT2) and the multireference singles and doubles configuration (MRSD-CI) levels of theory. The computed values of the electric hyperfine coupling constants for the (14)N atom in the ground state of the NCO radical agree well with the experimental data. The magnetic hyperfine coupling constants (HFCC's) have been estimated employing the configuration selected MRSD-CI and the multireference singles configuration interaction (MRS-CI) methods using iterative natural orbitals (ino) as one particle basis. Sufficiently accurate value of the isotropic contribution to the HFCC's can be obtained using an MRS-CI-ino procedure.     

Acidity and aniline alkylation activity of oxides and supported vanadia oxides

Aniline alkylation activity of simple oxides and supported vanadia oxides are compared from the point of view of acidity and vanadia-support interaction.

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IICT communication No. 2915     

Substituted thiosemicarbazido/semicarbazido quinolines as possible antimalarials

Several 2-aryl substituted thiosemicarbazido-4-methyl-6-methoxyquinolines and 2-aryl substituted semi-carbazido 4-methyl-6-methoxyquinolines were synthesized and evaluated for their antimalarial activity in mice infected with Plasmodium berghei. Two of these substituted quinolines were found to exhibit 50% clearance in a dose of 500 mg./kg. administered intraperitoneally for 5 days.     

Some new results on Unsymmetric Successive Overrelaxation method

Summary The Unsymmetric Successive Overrelaxation (USSOR) iterative method is applied to the solution of the system of linear equationsA x=b, whereA is annxn nonsingular matrix. We find the values of the relaxation parameters and for which the USSOR iterative method converges. Then we characterize those matrices which are equimodular toA and for which the USSOR iterative method converges.     

Synthesis of spiro[9,10-dihydro-10-sila-2-azaanthracene-9,1′-cyclopropanes

The Z- and E-isomers of 9,14dihydro-10,10-&-methyl-2-trimethylsilyl(2phenyl-3 fornryl)spiro[IO-sila-2-azaanthracene-9,1 -cyclopropane] have been obtained by heating 9-diazo-9,10-dihydro-10,10-dimethyl-10-sila-2azaanthracene with trimethylvinylsilane and with cinnanuaidehyde.     

Site-specific immobilization of flavin adenine dinucleotide on indium/tin oxide electrodes through flavin adenine amino group

A Mannich-type reaction was used to attach flavin adenine dinucleotide (FAD) covalently to aminosilane derivatized indium/tin oxide-coated glass plates. The aminosilane was activated with formaldehyde to give an intermediate that attached specifically to the adenine amino group of FAD. The presence of the intermediate also was demonstrated by coupling hydroquinone to the formaldehyde activated support. The immobilized FAD and hydroquinone were characterized by cyclic or differential pulse voltammetry. The immobilized FAD was shown to reduce the overpotential for NADH oxidation by 180 mV. In keeping with results for FAD on glassy carbon, FAD attached to indium/tin oxide at the adenine amino group did not lead to reconstitution of activity with apoglucose oxidase. On leave from University of Madras, India.