Double Schiff bases derivatives of chitosan by selective C-6 and C-2 oxidation mediated by 5-fluorosalicylaldehyde aniline by TG-GC-MS and TG-FTIR analysis

Abstract

This enhancement in the activity may be efficient on the basis that ligands mainly possess CH=N bond. The use of a structure-based drug design approach (SBDD) provides a way for investigation as well as to understand the molecular basis of the target protein and ligand molecule interactions at the atomic level. Structure-based drug design is the design and optimization of a chemical structure to identify a compound suitable for clinical testing the drug candidates. Chitosan is a polysaccharide with recognized biological activities for improving the functionality of polysaccharide 5-Fluorosalicylaldehyde aniline system. The used for selectively oxidized chitosan to produce tailored derivatives. C-2-5-Fluorosalicylaldehyde-C-6 aniline double Schiff base derivatives of chitosan were synthesized. The structure and properties of the newly synthesized product were characterized by FT-IR, ¹H-NMR, ¹³C-NMR, GC-Mass spectroscopy, and thermal analysis (DSC/TGA). An exothermic process discusses a DSC and TGA analysis of thermal behavior of this polymer was shown to be a possible thermal polymerization of the double bonds in the polymer chains and thermo-oxidation of the polymer.     

A Facile Reductive Cleavage of Allylic and Benzylic Esters with Low Valent Titanium Reagents

The reductive cleavage of allylic and benaylic esters 1a-g with titanium(II) reagent derived from Mg/Hg-TiCl yielded the corresponding acids 3a-g and dimeric hydro 4 carbons 2a-g under mild reaction conditions.     

A novel mixed valence iodide bridged Te(II)-Te(IV) complex featuring diisopropyldithiocarbamate(L) and iodide: ILTeII(I)TeIVL2I

The title compound is a novel mixed ligand and mixed valence complex of tellurium, the crystal structure of which is reported here. The compound crystallizes in the orthorhombic space group, Pca2₁ with four molecules per unit cell, the dimensions of which area=15.209(1),b=20.159(2),c=12.453(1) Å. The structure was solved by the heavy-atom method and refined by fullmatrix least-squares method to a finalR=0.046 andR _w=0.046 for 3011 unique reflections. The structure could be considered as 11 adduct of Te^IVL₂I₂ and Te^IILI (L=diisopropyldithiocarbamate). The two tellurium atoms, Te^II[Te(1)] and Te^IV[Te(2)] display entirely different coordinations and are bridged through iodine I(1) in a symmetrical manner. There is a short Te(1)Te(2) contact distance of 3.542(1) Å.     

Spatial and temporal variations of radon concentrations in groundwater of hard rock aquifers in Madurai district,India

Radon (²²²Rn) and other radionuclides in groundwater can lead to health problems if present in higher concentrations. A study was carried out in Madurai district of Tamilnadu by collecting groundwater samples for four different seasons and aims to identify the regions with higher ²²²Rn concentration along with their spatial and seasonal variations. ²²²Rn has been compared with field parameters, log pCO₂, major ions and uranium to detect the factors responsible for the higher concentration in groundwater. The weathering process induces the release of higher uranium ions from the granitic terrain from the rock matrix which enhances the ²²²Rn levels in groundwater.     

The influence of monovalent cations on the stability of electrochemically formed nickel fluoride films

The stability of electrochemically formed NiF₂ film in 1.0 M perchloric acid containing monovalent fluorides namely, NH₄F, HF, NaF, KF and LiF, is investigated using cyclic voltammetry, chronoamperometry, atomic absorption spectroscopy and scanning electron microscopy. In addition to direct dissolution of nickel and dissolution through the oxide layer, a new mode of dissolution of NiF₂ film as NiF₃ ⁻ and NiF₄ ²⁻ through complex formation is proposed. This process is significantly influenced by the alkali metal fluorides. On a comparative basis the stability of NiF₂ decreases in the order NH₄F > HF > KF > LiF. Received: 29 July 1998 / Accepted: 3 November 1998     

Electrochemical rectification at electrode surface modified with poly (acrylic acid) and decane thiol

Gold surface modified with a two-component system consisting of poly (acrylic acid) (PAA) by electropolymerizing acrylic acid (AA) and decane thiol (DT), further functionalized with ferrocene monocarboxylic acid (FMC) through covalent linkage, was used to demonstrate mediated electron transfer resulting in a unidirectional flow of current. The electrode surface was modified using two different configurations. In Configuration 1 (Config. 1), electrode surface modified with FMC showed rectification behavior when contacted with a solution containing methylene blue (MB). In Configuration 2, redox-active bilayer was constructed using polyvinyl pyrollidone (PVP) and hexaamineruthernium (II) chloride [Ru(NH₃)₆]²⁺ showed rectification characteristics. The continuous rectification property of the redox-active bilayer is achieved by releasing the trapped [Ru(NH₃)₆]³⁺ in the outer layer using a reductant (ascorbic acid). Spectroelectrochemical measurements were made to study the reduction property of the ascorbic acid. Atomic force microscopic images and impedance measurements were also made on the modified electrode surfaces to explore the compactness of the first layer (PAA and PAA/DT).     

Isonitrosopropiophenone as an ambidentate chelating agent in some transition metal complexes

Summary Isonitrosopropiophenonates of cobalt(III), cobalt(II), nickel(II) and palladium(II) have been synthesised and characterised. Isonitrosopropiophenonatonickel(II) exists as green and brown varieties, the green forming mono- as well as bispyridine adducts. The brown variety is obtained after removal of base from the adducts. I.r. data of the metal chelates suggest atrans-asymmetric structure involving N and O bonding for one form and atrans-symmetric structure involving either N or O bonding of the oximino-group for the other. The former is observed exclusively with isonitrosopropiophenonates of nickel(II) while the latter is common among the other metal chelates. The low magnetic moment of the mono-adduct is ascribed to super-exchange interaction between two metal ions through oxo-bridges in the dimer. Acis-octahedral structure has been assigned to the tris(isonitrosopropiophenonato) cobalt(III) on the basis of¹H n.m.r. data. Isonitrosopropiophenone forms mixed-ligand complexes of cobalt(III) with tetradentate Schiff bases such as SALEN,N,N-ethylenebis(salicylaldimine), and SALPN,N,N-1,3-propylenebis-(salicylaldimine), where the isonitrose group bonds through the nitrogen atom. These complexes have a N,N,N,O,O,O ligand environment. The imino-nickel(II) and -palladium(II) complexes are assigned atrans-symmetric square planar structure. Characterisation of the complexes was based upon elemental analyses, conductivity and magnetic moment, and i.r.,¹H n.m.r., and electronic spectra.     

Regioselective synthesis of mono- and bis-decahydrobenzocarbazoles via tandem reactions of α-diazo ketones

Regioselective intermolecular 1,3-dipolar cycloaddition reactions of rhodium generated carbonyl ylides with indoles are reported in this paper. Intermolecular 1,3-dipolar cycloaddition reactions of five-membered-ring cyclic carbonyl ylides with indole and substituted indoles afforded hexahydro-2H-carbazol-2-ones in a regioselective manner. Similarly, reactions of cyclic carbonyl ylides were carried out to afford decahydrobenzo[c]carbazoles or decahydrocyclopenta[c]carbazoles with high regioselectivity. Interestingly, the other possible regioisomer decahydrobenzo[a]carbazoles were also obtained by the reaction of cyclic carbonyl ylides and indoles having electron withdrawing substituents. The structure and stereochemistry of regioisomers 6,11c-epoxy-1,2,3,4,4a,5,6,6a,11b,11c-decahydro-4a-methyl-5-oxo-7H-benzo[c]carbazole and 11-benzenesulfonyl-6,11b-epoxy-2,3,4,4a,5,6,6a,11,11a,11b-decahydro-4a-methyl-5-oxo-1H-benzo[a]carbazole were unequivocally corroborated by single-crystal X-ray analyses. To advance this study, regioselective double 1,3-dipolar cycloaddition reaction of five-membered-ring cyclic carbonyl ylides has been demonstrated for the first time with biindoles having various aryl and alkyl spacers. This process constructed up to eight stereocenters, four carbon-carbon and two carbon-oxygen bonds in a single step with an excellent molecular complexity and stereoselectivity.     

Iron(II), cobalt(III), nickel(II) and copper(II) chelates of furan and thiophene azo-oximes

Summary Complexes of furan and thiophene azo-oximes with iron(II), cobalt(III), nickel(II) and copper(II) have been prepared and characterised. Iron(II), cobalt(III) and copper(II) complexes are diamagnetic in the solid state. The diamagnetism of the copper(II) chelates is suggestive of antiferromagnetic interaction between two copper centres.¹H n.m.r. spectral data suggest atrans-octahedral geometry for the tris-chelates of cobalt(III). Nickel(II) complexes are paramagnetic, in contrast to the diamagnetism of the analogous complexes of arylazooximes. The electronic spectra are suggestive of octahedral geometry for the iron(II), cobalt(III) and nickel(II) complexes, andD _4h -symmetry for copper(II). Infrared data indicate N-bonding of the oximino-group to the metal ions.