The synthesis and ligand properties of the dihydro-bis-(1-indazolyl)borate anion

Summary Potassium dihydro-bis-(1-indazolyl)borate, synthesized from potassium borohydride and indazole, has been used as a reagent to yield complexes with copper(II), nickel(II), cobalt(II), manganese(II) and iron(III) ions. From i.r. spectral studies the ligand is uninegative and bidentate and coordination occurs through the nitrogen atom at position 2 of the indazole ring system in all cases. With the sole exception of the copper(II) complex, the nitrogen atom at position 1 is also involved in forming a bridge with an adjacent metal ion. On the basis of electronic spectral studies and magnetic susceptibility measurements a distorted square planar structure involving chlorine bridges has been proposed for the copper complex. An octahedral geometry with ligand bridges for all complexes is tentatively proposed and it appears that all are polymers.     

Preparation,properties and x-ray crystal structure of a complex of bis(triphenylphosphoranylidene)ammonium iodide with 7,7,8,8-tetracyano-P-quinodimethane: (PPN)2(TCNQ)3(CH3CN)2

Bis(triphenylphosphoranylidene)ammonium iodide (PPN⁺I^?) forms a 2:3 complex with TCNQ [(PPN)₂(TCNQ)₃(CH₃CN)₂] that provides an example of a TCNQ complex containing acetonitrile in the crystal lattice; the material is a semi-conductor with trimerised TCNQ stacks.     

Polarographic reduction and tautomeric structure of 2-amino-5-arylazothiazoles

The polarographic behaviour of a series of 2-amino-4-phenyl-5-arylazothiazoles has been investigated at a dropping mercury electrode. Each of the compounds studied exhibits one wave which was shown to correspond to the reductive cleavage of the azo linkage by a 4e irreversible step. On the basis of the polarographic data, it was concluded that the compounds exist only in one tautomeric form, namely the aminoazo structure 1 . The results of E_1/2 — σ_X correlations and HMO calculations of bonding energies of the various possible tautomeric forms 1–3 indicate that the aminoazo form 1 is the most stable structure of the compounds examined.     

Integrated mean square properties of density estimation by orthogonal series methods for dependent variables

Summary The rates at which integrated mean square and mean squre errors of nonparametric density estimation by orthogonal series method for sequences of strictly stationary strong mixing random variables are obtained. These rates are better than those known to hold for the independent case and they are shown to hold for Markov processes. In fact our results when specialized to the independent case are improvements over previously known results of Schwartz (1967,Ann. Math. Statist.,38, 1262–1265). An extension of the results to estimation of the bivariate density is also given. Research supported by a faculty summer research grant MS-STAT-42 from the University of Petroleum and Minerals.     

Nanosecond Pulse Generation with Silver Nanoparticle Saturable Absorber

Nanosecond pulse generation in an erbium-doped fiber laser (EDFL) passively mode-locked by a silver nanoparticle(SNP)-based saturable absorber(SA) is experimentally demonstrated. The SA is fabricated by depositing a nanosized SNP layer onto the surface of polyvinyl alcohol film through the thermal evaporation process. By inserting the SA into an EDFL cavity, stable mode-locked operation is achieved at 1561.5 nm with the maximum pulse energy up to 52.3 nJ. The laser operates at a pulse repetition frequency of 1.0 MHz with a pulse width of 202 ns. These results suggest that SNPs could be developed as an effective SA for mode-locking pulse generation.     

Synthesis and Investigation of Derivatives of 1,8-Naphthalimide with a Red Emission via an Aromatic Nucleophilic Substitution Reaction

1,8-Napthalimides (NIs) have been widely used as fluorescent molecules in biological, chemical, and medical fields because NIs shows high stability and various fluorescence properties under different conditions. However, NIs typically display a fluorescence emission wavelength in the range of 350 – 550 nm which can be notably interfered with by autofluorescence in living cells, significantly limiting their bio-applications. Moreover, low solubility in aqueous media is another major limitation for NIs. In this project, four derivatives of NIs (1–4) have been synthesized via an aromatic nucleophilic substitution reaction and their photophysical properties have been investigated in various media (water, MeOH, MeCN, DMSO, EtOAc, and THF). All of these derivatives (1–4) show a long emission wavelength around 600 nm and high solubility in polar solvents. Particularly molecules (1–4) show the longest emission (624–629 nm) in water and the fluorescence intensity is not significantly varied in the range of pH 4–11. These unique features, long emission wavelength, high solubility, and high stability in difference pH media, will allow these derivative (1–4) to be used as excellent labeling reagents in the biological system.

     

Targeting the cytochrome bc1 complex for drug development in M. tuberculosis: review

Molecular Diversity - The terminal oxidases of the oxidative phosphorylation pathway play a significant role in the survival and growth of M. tuberculosis, targeting these components lead to...     

Precision measurement ofK-shell fluorescence yields in actinide elements

High-precision measurements ofK Auger electron andK x-ray intensities have been made for several transuranium elements and these have been used to determineK-shell fluorescence yields (ω _K ). The electron spectra were measured with a cooled Si(Li) spectrometer and the photon spectra were taken with Ge(Li) diodes. Very thin mass-separated samples of nuclides, which decay predominantly by electron capture, were used in the present experiments. From our present measurements the following values ofK- shell fluorescence yield have been obtained: Np, 97.2±0.3%; Pu, 97.2±0.4%; Cm, 97.1 ±0.6%; Bk, 97.1±0.4%; Cf, 97.3±0.4%; and Es, 97.2±0.5%. These numbers indicate that theK-fluorescence yield for elements in theZ=93 toZ=99 region remains constant within the experimental error. The weighted average of these numbers is 97.19% with external error of 0.03% and internal error of 0.17%. This value is in excellent agreement with known theoretical calculations.