Synthesis of 4-Dicyclohexylaminomethyl Antipyrine and Its Metal Complexes: Spectral Characterization and Evaluation of Thermodynamic Parameters

Complexes of Fe(III), Co(II), Ni(II), and Cu(II) with 4-dicyclohexylaminomethyl antipyrine (DCHAMA, L) were prepared and characterized by elemental and chemical analyses, IR, electronic absorption, ¹H NMR and EPR spectroscopies, thermal analysis, and magnetic susceptibility measurements. The stoichiometry of the complexes was found to be MLX₂, MLX₃, or MLX₂(H₂O)₂ where X = Cl or NO₃. The ligand exhibits a bidentate mode of coordination. Thermal analysis of the chloro complexes shows a three stage decomposition pattern for the Cu(II) complex and a two stage decomposition pattern for Fe(III) and Co(II) complexes to yield the respective metal oxides as the end product. Kinetic and thermodynamic parameters such as n, E _a, H ^#, S ^#, and G ^# were calculated using Coats–Redfern and Madhusudhanan–Krishnan–Ninan integral methods. The coordination number of the metal atom is found to influence the thermal stability of the complexes. The antimicrobial screening shows that the four-coordinated complexes are more active than the five- and six-coordinated ones and DCHAMA.     

Spectral,Thermal, and Antimicrobial Studies on the Copper(II), Zinc(II), Cadmium(II), and Mercury(II) Chelates of a New Antimetabolite–5-Dimethylaminomethyl-2-Thiouracil

Owing to the presence of multiple donor atoms such as N(1)H, C(2)SH, N(3), C(4)O, and CNC in the newly synthesized antimetabolite, namely, 5-dimethylaminomethyl-2-thiouracil, preferences of the hetero-atoms for coordination with metal ions like Cu(II), Zn(II), Cd(II), and Hg(II) were explored. The complexes isolated were characterized by chemical analysis and spectroscopic techniques. The ligand behaves as a bidentate/tetradentate chelating ligand. Invariably in all the complexes, one of the donor atoms is the soft C(2)SH. The kinetic and thermodynamic parameters for the thermal decomposition of the metal chelates were evaluated using (Coats–Redfern) and (Madhusudanan–Krishnan–Ninan) equations. The antimicrobial studies show that the copper(II) complexes are more active than the other complexes.     

Stability characteristics of aqueous chloramine-T solutions

Aqueous chloramine-T solutions in strongly alkaline medium are quite stable even up to 60 degrees . In 0.2-2 M sulphuric or perchloric acid at 25-30 degrees , there is no loss in titre, but in hydrochloric acid solutions > 0-5M, there is a loss in titre which increases with increase in hydrochloric acid concentration. This is ascribed to oxidation of chloride to chlorine. In the pH range 2.65-5.65 there is a small but reproducible loss in oxidative titre which is maximal at pH 4.7. This is ascribed to side-reactions occurring during partial disproportionation of monochloramine-T to dichloramine-T and p-toluenesulphonamide.     

Estimation of dimethylsulphoxide with chloramine-T

A rapid and accurate method for the estimation of dimethyl-sulphoxide has been developed based on its oxidation to dimethyl-sulphone at room temperature by chloramine-T at pH 4-4.5. The effect of variables such as the pH, the mode of addition of reagents and the concentration of chloride ion on the extent and nature of oxidation has been studied and optimal conditons for analytical determination of dimethylsulphoxide derived.     

Investigations on membrane perturbation by chrysin and its copper complex using self-assembled lipid bilayers

The mechanism of membrane interactions of most of the flavonoids in the presence of transition-metal ions is not well-understood. To understand this phenomenon, the present work aims to synthesize a chrysin-copper complex at room temperature and investigate its influence on the electrical characteristics of planar lipid bilayers. The chrysin-copper complex was characterized by various spectroscopic techniques and was found to have a metal/ligand ratio of 1:2 and of cationic nature. Its ability to inhibit 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radicals was not significant at alkaline pH because of the involvement of the 5-hydroxy group in coordination with the copper ion compared to its parent flavonoid, chrysin (p < 0.05). The addition of different concentrations (20-100 μM) of chrysin and the chrysin-copper complex to lipid bilayers decreases the resistance, indicating a strong surface interaction and partial insertion into the bilayer near the lipid-water interface. The dose-dependent reduction in resistance as a result of the chrysin-copper complex is more pronounced in comparison to chrysin, implying that the bulkier and charged chrysin-copper complex displays greater ability to distort the lipid bilayer architecture. These conclusions were further confirmed by curcumin-loaded liposome permeabilization studies, where both chrysin and its Cu(II) complex increased the fluidity in a dose-dependent manner. However, the extent of fluidization by the chrysin-copper complex was nearly twice that of chrysin alone (p < 0.05). The implications of these surface interactions of chrysin and its copper complex on cell membranes were studied using a hypotonic hemolysis assay. Our results demonstrate that, at low concentrations (20 μM), the chrysin-copper complex exhibited twice the protection against hypotonic stress-induced membrane disruption when compared to chrysin. However, this stabilizing effect gradually decreased and became comparable to chrysin at higher concentrations. This biphasic behavior of the chrysin-copper complex could further be explored for therapeutic applications.     

Determination of iodide with chloramine-T

A method is described for the estimation of iodide, based on its oxidation to iodate by the addition of excess of chloramine-T, destruction of the excess of chloraniine-T with dimethyl sulphoxide and determination of the iodate iodometrically. In addition, the dimethyl sulphoxide eliminates any interference from bromide or bromate.