Synthesis, spectral studies and antibacterial activity of novel macrocyclic Co(II) compounds

Ten novel macrocyclic Co(II) compounds have been synthesized by treating four N(4) and six N(2)O(2) donor macrocycles with cobalt chloride in methanol. These compounds were characterized by elemental, IR, (1)H, (13)C NMR, mass, electronic spectral analysis, molar conductance and magnetic susceptibility measurements. Thermal behavior of these compounds has been studied by the thermogravimetric analysis. An octahedral geometry has been proposed for all of these complexes. All the macrocycles and macrocyclic Co(II) compounds along with existing antibacterial drugs were screened for antibacterial activity against Gram +ve and Gram -ve bacteria. All these compounds were found to be more active when compared to streptomycin and ampicillin.     

Stereoselective synthesis of C19–C27 fragment of bryostatin 11

A convergent synthesis of C19–C27 fragment (2) of bryostatin-11 is described. The key steps involved in this approach are kinetic resolution, Grignard reaction, and Sharpless dihydroxylation. AIBN catalyzed radical cyclization strategy has been used for the first time to construct the six-membered pyran system.     

Cation‐ and Anion‐Substituted Potassium Manganese Phosphate,KMnP3O9: Luminescence and Photocatalytic Studies

Phosphates as multifunctional materials were of vital importance in the environmental and energy fields. In the present work, a new cyclophosphate, potassium manganese phosphate (KMnP₃O₉) (hereafter KMPO), was prepared by solid state method. Cations (Ag⁺ and Cu²⁺) and anion (N^3?) were substituted into KMPO lattice via ion‐exchange and solid state methods, respectively. The as‐prepared materials were characterized by powder X–ray diffraction, SEM–EDS and UV–visible diffuse reflectance spectra. Rietveld refinement was carried out for parent material. All the prepared materials were found to crystallize in the hexagonal lattice and isomorphous with KCoP₃O₉. The nitrogen content in N^3?‐substituted KMPO was estimated by EDS and O‐N‐H analysis. The bandgap energy of the cation‐ and anion‐substituted samples was lower compared to that of pristine KMPO. Gouy method was employed to determine the magnetic susceptibility of KMPO. The photoluminescence property of Mn²⁺ in all the samples was studied, and the color coordinates were calculated using CIE 1931 chromaticity. The photocatalytic activity of visible light active material, N^3?‐substituted KMPO, was examined against the degradation of methylene blue and methyl violet at ambient conditions.     

Synthesis,spectral studies,and catalytic and antibacterial activity of Ru(II) complexes with coordinated amides

Twelve Ru(II) complexes with coordinated amides were synthesized and characterized by elemental, IR, ¹H, ¹³C, ³¹P NMR, mass, and electronic spectral analysis, along with magnetic and conductance measurements. Molecular formulas and octahedral structures have been tentatively proposed. These complexes were used as catalysts for the hydrolysis of rivastigmine and neostigmine. The hydrolyzed products were coupled with 3-methyl benzothiazolinone hydrazone reagent in the presence of sodium metaperiodate and the resulting colored products were determined spectrophotometrically. The yields of hydrolyzed products were found to be 98.47% and 99.75% respectively. All the ligands and Ru(II) complexes were screened for antibacterial activity. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 867–874, November–December, 2008.     

Cerium Alkoxides—Synthesis, Properties and Their Use in Michael Addition Reaction

Cerium(III) alkoxides served as an effective and attractive promoter for the Michael addition reaction with excellent chemical yields under mild conditions in short reaction time.     

Lower bounds for the spread of a matrix

A characterization of the spread of a normal matrix is used to derive several simple lower bounds for the spread. Comparisons are then made with several known bounds.     

T1ρ-weighted MRI using a surface coil to transmit spin-lock pulses

T1rho-weighted MRI is a novel basis for generating tissue contrast. However, it suffers from sensitivity to B1 inhomogeneity. First, excitation with a spatially varying B1 causes flip-angle artifacts and second, spin locking with an inhomogeneous B1 results in non-uniform T1rho contrast. In this study, we overcome the former complication with a specially designed spin-locking pulse sequence and we successfully obtain T1rho-weighted images with a surface coil. In this pulse sequence, the spin-lock pulse was divided into segments of equal duration and alternating phase. This "self-compensating" T1rho-preparatory pulse sequence was analyzed and the effect of an inhomogeneous B1 field was simulated using the Bloch equations. T1rho-weighted MR images of a phantom and a human knee joint in vivo were obtained on a clinical scanner with a surface coil to demonstrate the utility of the pulse sequence. The self-compensating T1rho-prepared pulses sequence resulted in substantially reduced image artifacts compared to the conventional, single-phase spin-lock pulse.     

Zirconyl Chloride (= Dichlorooxozirconium) as an Efficient Catalyst for One‐Pot Multicomponent Synthesis of Homoallylic Amines

Zirconyl chloride (ZrOCl₂) catalyzes efficiently the one‐pot three component reactions of aldehydes, amines, and allyltributylstannane at room temperature to furnish the corresponding homoallylic amines in short reaction times and in excellent yields.     

Hypervalent iodine-mediated interaction of aldoximes with activated alkenes including Baylis-Hillman adducts: a new and efficient method for the preparation of nitrile oxides from aldoximes

Treatment of aldoximes with activated alkenes in the presence of diacetoxy iodobenzene (DIB) afforded isoxazolines in high yields. The method has been applied for the preparation of polyfunctional isoxazolines from Baylis-Hillman adducts.     

PHOTOBLEACHING OF MEROCYANINE 540: INVOLVEMENT OF SINGLET MOLECULAR OXYGEN

The purpose of this study was to assess the mechanism of merocyanine 540 (MC540) photobleaching in a liposomal system. Broad based visible irradiation of MC540 in unilamellar dilauroylphosphatidylcholine (DLPC) vesicles resulted in dye bleaching that was strictly O2 dependent. The rate of self-sensitized photobleaching was enhanced in D2O and inhibited by both azide and histidine, consistent with 1O2 intermediacy (Type II chemistry). Supportive evidence for this mechanism was obtained by using a Type II sensitizer, aluminum phthalocyanine tetrasulfonate (AlPcS lambda max = 678 nm). Irradiation of AlPcS and MC540 in DLPC with lambda greater than 630 nm (absorbed only by AlPcS) light resulted in rapid bleaching of MC540, which was stimulated by D2O and inhibited by azide. A rate constant of 10(7) M-1 s-1 was determined for the chemical quenching of 1O2 by MC540. The rate constant for physical quenching of 1O2 by MC540 was estimated to be ca 10(9) M-1 s-1.