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1.
The copper(II/I) complexes of hexathiaether macrocyclic ligand, 1,4,8,11,15,18-hexathiacyclohenicosane ([21]aneS6), were synthesized, and characterized by electrochemical and spectroscopic techniques. Cyclic voltammetric studies indicate that Cu([21]aneS6)2+/+ forms a reversible one-electron redox couple. The electrochemical potential obtained for Cu([21]aneS6)2+/+ (Ef = 0.89 V, against SHE) was found to be the highest potential reported to date for a Cu2+/+ macrocyclic system in aqueous solution. By employing the Nernst equation, we can infer that the practical upper limit for formal potential of Cu(II/I)L systems maybe close to this high value. Stability constant data obtained for these complexes indicate that Cu([21]aneS6)+is 12 orders of magnitude greater in stability than that of Cu([21]aneS6)2+ indicating the favorable nature of this large macrocyclic ligand towards formation of Cu(I) complexes over Cu(II) complexes. Crystal structure of Cu([21]aneS6)+ ( Fig. 2) shows that four sulfurs adjacent to one another are coordinated to Cu+ ion in this complex. Bond angles and distances calculated for the crystal indicate that it is a distorted tetrahedron, a geometry commonly encountered by Cu(I) complexes. This is the first report of synthesis and characterization of a metal coordinated [21]aneS6 complex. 相似文献
2.
K. Devika R. Chandrika Srirupa Mukherjee D. Padmanabhan V. K. P. Unny N. Sivaprasad 《Journal of Radioanalytical and Nuclear Chemistry》2006,267(3):581-583
Summary Tritiated uracil and uridine have been prepared simultaneously from a mixture of their respective halogenated analogues (5-bromouracil
and5-bromouridine) by halogen-tritium exchange in a one pot preparation, followed by purification. The tritiated products
thus obtained have specific activities of 0.962 TBq/mmol and 1.036 TBq/mmol, respectively. 相似文献
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4.
Chandrika Nanjappa Gopalpur Nagendrappa Pasura Subbaiah Sujan Ganapathy Shirur Dakappa Shruthi Sunil S. More 《合成通讯》2013,43(22):2529-2545
A new 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)-radical scavenging and antiproliferative agents of pyrrolo[1,2-a]quinoline derivatives have been synthesized. An efficient method for the synthesis of 14 novel diversified pyrrolo[1,2-a]quinoline derivatives has been described using 4-(1,3-dioxolan-2-yl)quinoline and different phenacyl bromides in acetone and followed by reacting with different acetylenes in dimethylformamide/K2CO3. The structure of the newly synthesized compounds was determined by infrared, 1H NMR, 13C NMR, mass spectrometry, and elemental analysis. The in vitro antioxidant activity revealed that among all the tested compounds 5n exhibited maximum scavenging activity with ABTS. Compound 5b has showed good antiproliferative activity as an inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase. 相似文献
5.
K. Devika R. Chandrika D. Padmanabhan V. K. P. Unny N. Sivaprasad 《Journal of Radioanalytical and Nuclear Chemistry》2005,266(3):507-508
Summary Tritiated fluorenone 2 was prepared from 2-iodofluorenone 1 by halogen-tritium exchange. The product had specific activity
of 17 Ci/mmol. The product 2(after dilution with unlabeled congener) on reduction with NaBH4gave the corresponding tritiated fluorenol 3. 相似文献
6.
Thirumavalavan M Akilan P Kandaswamy M Chinnakali K Kumar GS Fun HK 《Inorganic chemistry》2003,42(10):3308-3317
A series of putative mono- and binuclear copper(II) complexes, of general formulas [CuL](ClO(4)) and [Cu(2)L](ClO(4))(2), respectively, have been synthesized from lateral macrocyclic ligands that have different compartments, originated from their corresponding precursor compounds (PC-1, 3,4:9,10-dibenzo-1,12-[N,N'-bis[(3-formyl-2-hydroxy-5-methyl)benzyl]diaza]-5,8-dioxacyclotetradecane; and PC-2, 3,4:9,10-dibenzo-1,12-[N,N'-bis[(3-formyl-2-hydroxy-5-methyl)benzyl]diaza]-5,8-dioxacyclopentadecane). The precursor compound PC-1 crystallized in the triclinic system with space group P(-)1. The mononuclear copper(II) complex [CuL(1a)](ClO(4)) is crystallized in the monoclinic system with space group P2(1)/c. The binuclear copper(II) complex [Cu(2)L(2c)](ClO(4))(2) is crystallized in the triclinic system with space group P(-)1; the two Cu ions have two different geometries. Electrochemical studies evidenced that one quasi-reversible reduction wave (E(pc) = -0.78 to -0.87 V) for mononuclear complexes and two quasi-reversible one-electron-transfer reduction waves (E(1)(pc) = -0.83 to -0.92 V, E(2)(pc) = -1.07 to -1.38 V) for binuclear complexes are obtained in the cathodic region. Room-temperature magnetic-moment studies convey the presence of antiferromagnetic coupling in binuclear complexes [mu(eff) = (1.45-1.55)mu(B)], which is also suggested from the broad ESR spectra with g = 2.10-2.11, whereas mononuclear complexes show hyperfine splitting in ESR spectra and they have magnetic-moment values that are similar to the spin-only value [mu(eff) = (1.69-1.72)mu(B)]. Variable-temperature magnetic susceptibility study of the complex shows that the observed -2J value for the binuclear complex [Cu(2)L(1b)](ClO(4))(2) is 214 cm(-1). The observed initial rate-constant values of catechol oxidation, using complexes as catalysts, range from 4.89 x 10(-3) to 5.32 x 10(-2) min(-1) and the values are found to be higher for binuclear complexes than for the corresponding mononuclear complexes. 相似文献
7.
Aqueous solutions of copper(II) sulfate have been studied by dielectric relaxation spectroscopy (DRS) over a wide range of frequencies (0.2 less, similar nu/GHz < or = 89), concentrations (0.02 < or = m/mol kg(-1) less, similar 1.4), and temperatures (5 < or = t/ degrees C < or = 65). The spectra show clear evidence for the simultaneous existence of double-solvent-separated, solvent-shared, and contact ion pairs at all temperatures, with increasing formation especially of contact ion pairs with increasing temperature. The overall ion association constant corresponding to the equilibrium: Cu2+(aq) + SO4(2-)(aq) right harpoon over left harpoon CuSO4(0)(aq) was found to be in excellent agreement with literature data over the investigated temperature range. However, the precision of the spectra and other difficulties did not allow a thermodynamic analysis of the formation of the individual ion-pair types. Effective hydration numbers derived from the DRS spectra were high but consistent with simulation and diffraction data from the literature. They indicate that both ions influence solvent water molecules beyond the first hydration sphere. The implications of the present findings for previous observations on copper sulfate solutions are briefly discussed. 相似文献
8.
Chandrika B Schnackenberg LK Raveendran P Wallen SL 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(21):6266-6271
High pressure (HP), high resolution (HR), proton nuclear magnetic resonance (1H NMR) spectroscopy has been utilized for the first time to investigate the solution structure of a carbohydrate based system, sucrose octaacetate (SOA), in supercritical CO2. The studies indicate that the average solution state conformation of the alpha-D-Glucopyranosyl ring of SOA in scCO2 medium is consistent with the 4C1 chair form, while the beta-D-fructofuranosyl ring adopts an envelope conformation. The investigations also suggest that scCO2 is a promising medium to study the solution structure and conformation of acetylated sugar systems. Spectral manifestations of a specific interaction between the acetate methyl protons and CO2 molecules are also presented. 相似文献
9.
Saravanan Vinnarasi Rajamani Akilan Subramaniam Vijayakumar Ramasamy Shankar 《Structural chemistry》2020,31(1):465-484
Structural Chemistry - The present study is focused to cast light on the structural, electronic and energetic properties of isolated (G4)2 and (X4)2 DNA quadruplexes with transition metal cations... 相似文献
10.
Annamaria Giorgi Alessandra Manzo Niranjala Nanayakkarawasam Masachchige Chandrika Nanayakkara Luca Giupponi Maurizio Cocucci Sara Panseri 《Natural product research》2015,29(18):1695-1702
This study describes the application of headspace solid-phase microextraction (HS-SPME)–gas chromatography/mass spectrometry (GC/MS) to characterise the volatile fingerprint changes of Achillea collina, induced by aphids' infestation, mechanical damage and jasmonic acid (JA) treatment. The volatile organic compound profiles of A. collina, Prunus persica and Pisum sativum infested by Myzus persicae were also compared. Several changes were observed between control, infested, mechanically damaged and JA-treated plants, and new inducible volatile organic compounds (IVOCs) were emitted in response to biotic or abiotic stresses. Some of these were in common for all stresses and other compounds were in common only for two types of stress. Conversely some IVOCs were emitted only in response to the specific stimuli. The results suggested that there were species-specific and common IVOCs emitted by A. collina, P. persica and P. sativum in response to M. persicae infestation. In conclusion, HS-SPME–GC/MS seems to be a reliable analytical approach to study in vivo plant reaction to external stimuli. 相似文献