Spectroscopic and antimicrobial studies of macrocyclic metal complexes derived from 1,8-diaminonaphthalene and dimedone

A new series of macrocyclic metal complexes have been synthesized and characterized by the template condensation reaction of 1,8-diaminonaphthalene and dimedone in presence of divalent transition metals, resulting into the formation of the macrocyclic complexes of the type: [M(C₃₆H₃₆N₄)X₂]; where M = Co(II), Ni(II), Cu(II), Zn(II) and X = Cl^?, NO₃ ^?, CH₃COO^?. The synthesized macrocyclic complexes have been characterized with the aid of elemental analysis, conductance measurements, magnetic susceptibility measurements, electronic, infrared, NMR, Mass and ESR spectral studies. The complexes were also investigated for their fluorescence activity. Electronic spectra along with magnetic moments suggest the six coordinated octahedral geometry for all these complexes. The low value of molar conductance indicates them to be non-electrolyte. The in vitro antimicrobial activities of these macrocyclic complexes have also been investigated against some bacterial strains and yeast. Further minimum inhibitory concentration shown by these complexes against these pathogens was compared with MIC shown by standard antibiotic and standard antifungal drug.     

A Validated Stability-Indicating TLC Method for Determination of Forskolin in Crude Drug and Pharmaceutical Dosage Form

A simple, accurate, selective, precise, economical and stability-indicating high-performance thin-layer chromatographic method for analysis of forskolin in crude drug and in pharmaceutical dosage form was developed and validated. The method was developed on TLC aluminium plates precoated with silica gel 60F-254 using solvent system benzene:methanol (9:1, v/v), which gives compact spot of forskolin (R _f value 0.25 ± 0.02). Densitometric analysis of forskolin was carried out in the absorbance mode at 545 nm after spraying with anisaldehyde sulphuric acid. The linear regression analysis data for the calibration plots showed good linear relationship with r = 0.994 and 0.994 with respect to peak height and peak area, respectively, in the concentration range 100–1,000 ng per spot. The limits of detection and quantification were 8.1 and 26.9 ng per spot, respectively. The proposed method was applied for determination of forskolin in Coleus forskohlii root and in capsule dosage forms, which showed 0.18 and 0.57% w/w of forskolin. Forskolin was subjected to acid and alkali hydrolysis, oxidation, photodegradation and heat degradation. It was observed that the drug is susceptible to acid, base hydrolysis, oxidation, photo-oxidation and heat degradation. Statistical analysis proves that the method is repeatable, selective and accurate for the estimation of forskolin in crude drug and in pharmaceutical dosage forms. The developed method effectively resolved the forskolin from components of C. forskohlii root, from excipients of capsule as well as the degradation products of forskolin hence, it can be employed for routine analysis and as a stability-indicating method.     

Effects of anionic and cationic micelles on the oxidation of d-dextrose by diperiodatoargentate(III)

The oxidative behavior of d-dextrose toward diperiodatoargentate(III) (DPA) has been studied in the absence and presence of anionic and cationic micelles of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), respectively. The kinetics is based on the reduction of silver(III) to silver(I) by d-dextrose under pseudo-first-order conditions. The monoperiodatoargentate(III) ions act as active oxidants in comparison to that of DPA. The reactions are first- and fractional-order dependence with respect to [DPA] and [d-dextrose], respectively. The reaction rates decrease with [H⁺] and [periodate]. The premicellar environment of SDS and CTAB strongly inhibits the reaction rate. Inhibition is due to favorable thermodynamic/electrostatic binding between the Ag(III) complex and CTAB monomer aggregates. A suitable mechanism involving a one-electron transfer (rate-determining step) from d-dextrose to the silver(III) species has been proposed. Activation parameters have been evaluated and discussed.     

Unusual stabilization of water-soluble colloidal MnO2 during the oxidation of paracetamol by

The kinetics of the formation and decomposition of water-soluble colloidal MnO₂ in the paracetamol– redox system have been investigated spectrophotometrically in aqueous-neutral media at 30 °C. Upon mixing aqueous solutions of permanganate and paracetamol, a readily distinguishable brown color appears and then disappears slowly. Experiments have been done to confirm the nature of intermediate (Mn(IV)) formed during the reduction of permanganate by paracetamol. The stoichiometry was found to be 1:1. Formation and decomposition of water-soluble colloidal MnO₂ depend upon the experimental conditions, i.e., [paracetamol] and [H⁺]. The effect of total [paracetamol], and [H⁺] on the rate of the reaction was determined. On the basis of various observations, two mechanisms are proposed: one for MnO₂ formation and the other for decomposition.     

Synthesis and characterisation of four- and six-membered P-Se heterocycles

The preparation, spectroscopic characterisation and crystal structures of [FcP(mu-Se)Se]2, [FcP(mu-Se2)Se]2 and [PhP(mu-Se2)Se]2 are reported. Crystallographic data reveal planar four-membered PSePSe and skewed six-membered P2Se4 rings, respectively, in all cases with trans arrangement of organic substituents and exo selenium atoms. Whilst stable at room temperature in solid state, NMR data suggest the six-membered rings of both the ferrocenyl and phenyl compounds decompose in the solution with loss of red selenium, forming PSe2PSe five-membered rings.     

Exact analytic solutions for the unsteady flow of a non-Newtonian fluid between two cylinders with fractional derivative model

The velocity field and the associated shear stress corresponding to the torsional oscillatory flow of a generalized Maxwell fluid, between two infinite coaxial circular cylinders, are determined by means of the Laplace and Hankel transforms. Initially, the fluid and cylinders are at rest and after some time both cylinders suddenly begin to oscillate around their common axis with different angular frequencies of their velocities. The solutions that have been obtained are presented under integral and series forms in terms of generalized G and R functions. Moreover, these solutions satisfy the governing differential equation and all imposed initial and boundary conditions. The respective solutions for the motion between the cylinders, when one of them is at rest, can be obtained from our general solutions. Furthermore, the corresponding solutions for the similar flow of ordinary Maxwell fluid are also obtained as limiting cases of our general solutions. At the end, flows corresponding to the ordinary Maxwell and generalized Maxwell fluids are shown and compared graphically by plotting velocity profiles at different values of time and some important results are remarked.     

Visible Light Promoted Iron-Catalyzed One-Pot Synthesis of 2-Arylimino-2H-Chromenes from 2-Hydroxybenzyl Alcohols and β- Ketothioamides at Room Temperature

An efficient, environmentally benign and one-pot approach for the synthesis of 2-arylimino-2H-chromenes from 2-hydroxybenzyl alcohols and β-ketothioamides at room temperature under visible light has been developed. The reported reaction conditions were favorable for a wide range of β-ketothioamides afforded good to excellent yields of the respective products. The low cost and air stable Knölker iron catalyst has been employed for the dehydrogenation of 2-hydroxybenzyl alcohols under photolysis that would usually require a higher temperature.