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71.
Summary Base hydrolysis of the bis(ethylenediamine)thiosulphatocobalt(III) was investigated spectrophotometrically between 35 and 65 °C and with base concentrations (NaOH) up to 2.0 mol dm–3. The hydrolysis consists of a one-stage reaction, followed by a slow dechelation step, and then by a fast ligand loss. The reaction is base-dependent. The products of the reaction are an equilibrium mixture ofcis- andtrans-Coen2 (OH)
2
+
. Activation parameters for the reaction as determined by the Eyring equation, are H=77.8±4.6 kJ mol–1 and S=–75±20 JK–1 mol–1. 相似文献
72.
Dhar S Senapati D Reddy PA Das PK Chakravarty AR 《Chemical communications (Cambridge, England)》2003,(19):2452-2453
Complete cleavage of double stranded pUC19 DNA by the complex [Cu(dpq)2(H2O)](ClO4)2 (dpq, dipyridoquinoxaline) has been observed on irradiation at 694 nm from a pulsed ruby laser, assisted by the metal d-band transition as well as the quinoxaline triplet states in the absence of any external additives. 相似文献
73.
Manirul Islam Sanchita Mondal Paramita Mondal Anupam Singha Roy Dildar Hossain Manir Mobarak 《Transition Metal Chemistry》2011,36(1):1-11
Two copper complexes were synthesized from macroporous chloromethylated polystyrene beads. The first one was prepared by sequential
attachment of imidazole and copper acetate with chloromethylated polystyrene-divinyl benzene copolymer, and the second one
was prepared from 4-vinylpyridine and copper acetate with chloromethylated polystyrene-divinyl benzene copolymer. These catalysts
showed excellent catalytic activity in O-arylation reaction of aryl halides with phenol in dimethylsulfoxide using potassium
carbonate at 130 °C under open air conditions to give diaryl ethers in high yields. Less reactive aryl bromides and aryl chlorides
have also been shown to react with phenols to give good yields of the diaryl ethers. The effects of various parameters such
as solvent, catalyst from different copper salt and base on the reaction system were studied. The reaction is applicable to
a wide variety of substituted aryl halides and phenols with different steric and electronic properties. These catalysts were
recovered by simple filtration, and the reusability experiments showed that these catalysts can be used five times without
much loss in the catalytic activity. 相似文献
74.
Summary Substitution of the halide ion of [Ru(NH3)5X]2+ (X=Cl– or Br–) by SeCN– was monitored spectrophotometrically between 45 and 60° C in aqueous medium. The pseudo-first order rate constants were evaluated by Guggenheim's procedure, which shows linearity for 2–3 half-lives. The rate increases linearly with [SeCN–] and all the plots have a positive intercept on the rate axis. The SeCN–-independent path represents aquation and the SeCN–-dependent path represents anation of the aqua complex with simultaneous formation of two isomeric (the N bonded and the Se bonded) products. The formation of the isomeric products is entropy controlled. 相似文献
75.
Mukherjee A Raghunathan R Saha MK Nethaji M Ramasesha S Chakravarty AR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(10):3087-3096
Three cubane copper(II) clusters, namely [Cu(4)(HL')4] (1), [Cu4L2(OH)2] (2), and [Cu4L2(OMe)2] (3), of two pentadentate Schiff-base ligands N,N'-(2-hydroxypropane-1,3-diyl)bis(acetylacetoneimine) (H3L') and N,N'-(2-hydroxypropane-1,3-diyl)bis(salicylaldimine) (H3L), are prepared, structurally characterized by X-ray crystallography, and their variable-temperature magnetic properties studied. Complex 1 has a metal-to-ligand stoichiometry of 1:1 and it crystallizes in the cubic space group P43n with a structure that consists of a tetranuclear core with metal centers linked by a mu(3)-alkoxo oxygen atom to form a cubic arrangement of the metal and oxygen atoms. Each ligand displays a tridentate binding mode which means that a total of eight pendant binding sites remain per cubane molecule. Complexes [Cu4L2(OH)2] (2) and [Cu4L2(OMe)2] (3) crystallize in the orthorhombic space group Pccn and have a cubane structure that is formed by the self-assembly of two {Cu2L}+ units. The variable-temperature magnetic susceptibility data in the range 300-18 K show ferromagnetic exchange interactions in the complexes. Along with the ferromagnetic exchange pathway, there is also a weak antiferromagnetic exchange between the copper centers. The theoretical fitting of the magnetic data gives the following parameters: J1 = 38.5 and J2 = -18 cm(-1) for 1 with a triplet (S = 1) ground state and quintet (S = 2) lowest excited state; J1 = 14.7 and J2 = -18.4 cm(-1) for 2 with a triplet ground state and singlet (S = 0) lowest excited state; and J1 = 33.3 and J2 = -15.6 cm(-1) for 3 with a triplet ground state and quintet lowest excited state, where J1 and J2 are two different exchange pathways in the cubane {Cu4O4} core. The crystal structures of 2 * 6 H2O and 3 * 2 H2O * THF show the presence of channels containing the lattice solvent molecules. 相似文献
76.
Debojyoti Lahiri Tuhin Bhowmick Bhabatosh Banik Reema Railkar Suryanarayanarao Ramakumar Rajan R. Dighe Akhil R. Chakravarty 《Polyhedron》2010
Dicobalt(II) complexes [{(B)CoII}2(μ-dtdp)2] (1–3) of 3,3′-dithiodipropionic acid (dtdp) and phenanthroline bases (B), viz. 1,10-phenanthroline (phen in 1), dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq in 2) and dipyrido[3,2-a:2′,3′-c]phenazine (dppz in 3), have been prepared, characterized and their photo-induced anaerobic DNA cleavage activity studied. The elemental analysis and mass spectral data suggest binuclear formulation of the complexes. The redox inactive complexes have magnetically non-interacting dicobalt(II) core showing magnetic moment of ∼3.9 μB per cobalt(II) center. The complexes show good binding propensity to calf thymus DNA giving Kb values within 4.3 × 105–4.0 × 106 M−1. Thermal melting and viscosity data predict DNA groove binding and/or partial intercalative nature of the complexes. The complexes show significant anaerobic DNA cleavage activity in green light under argon atmosphere possibly involving radical species generated from the disulfide moiety in a type-I pathway. The DNA cleavage reaction under aerobic medium in green light is found to involve hydroxyl radical species. The dppz complex 3 exhibits significant photocytotoxicity in HeLa cervical cancer cells with an IC50 value of 2.3 μM in UV-A light of 365 nm, while it is essentially non-toxic in dark giving an IC50 value of >200 μM. A significant reduction of the dark toxicity of the organic dppz base (IC50 = 8.3 μM in dark) is observed on binding to the cobalt(II) center while essentially retaining its photocytotoxicity in UV-A light (IC50 = 0.4 μM). 相似文献
77.
Copper(II) complexes [Cu(ph-tpy)(B)](ClO4) (1–3), where ph-tpy is (4′-phenyl)-2,2′:6′,2″-terpyridine and B is N,N-donor phenanthroline base, viz. 1,10-phenanthroline (phen, 1), dipyridoquinoxaline (dpq, 2), and dipyridophenazine (dppz, 3), were prepared and characterized from analytical and spectral data. Complex 1, characterized by X-ray crystallography, shows a distorted square-pyramidal (4 + 1) CuN5 coordination geometry having the tridentate ph-tpy ligand at the basal plane and bidentate phen bound to the axial-equatorial sites. The complexes display a d–d band near 650 nm in aqueous DMF. The complexes are avid binders to calf thymus DNA giving the binding order: 3 (dppz) > 2 (dpq) > 1 (phen). The dpq and dppz complexes show photo-induced DNA cleavage activity in red light via photo-redox pathway forming hydroxyl radicals. The cytotoxicity of the dppz complex 3 was studied by MTT assay in HeLa cancer cells. The IC50 values are 3.7 and 12.4 μM in visible light of 400–700 nm and dark, respectively. 相似文献
78.
Summary The kinetics of the reaction betweencis-dichlorobisbipyridineruthenium(II) and nitric acid have been investigated spectrophotometrically in the 25°–40° range in the presence of 0.03 to 0.2 mol dm–3 HNO3. The reaction proceeds with the stepwise formation of monoaqua and diaqua products. Only the formation of the monoaqua intermediate was followed as this species could not be obtained in a pure state. Aquation proceeds through a dissociative process. The second order rate constants are 11.8 (25°), 17.5 (30°); 30.0 (35°) l mol–1 s–1. Activation parameters are H 52±3 kJ mol–1; S–108±8 JK–1 mol–1. 相似文献
79.
Aranyak Chakravarty Priyankan Datta Koushik Ghosh Swarnendu Sen Achintya Mukhopadhyay 《Transport in Porous Media》2017,116(1):353-377
Natural convection in enclosures driven by heat-generating porous media has diverse applications in fields like geothermal, chemical, thermal and nuclear energy. The present article focuses on heat transfer and entropy generation characteristics of a heat-generating porous bed, placed centrally within a fluid-filled cylindrical enclosure. Pressure drop and heat transfer in the porous bed are modelled using the Darcy–Brinkmann–Forchheimer approximation and the local thermal non-equilibrium model, respectively. Energy flux vectors have been utilised for visualising convective energy transfer within the enclosure. The study of a wide range of Rayleigh number (\(10^{7}\)–\(10^{11}\)) and Darcy number (\(10^{-6}\)–\(10^{-10}\)) reveals that heat transfer in the porous region can be classified into conduction-dominated and convection-dominated regimes. This is supplemented with an entropy generation analysis in order to identify and characterise the irreversibilities associated with the phenomenon. It is observed that entropy generation characteristics of the enclosure closely follow the above-mentioned regime demarcation. Numerical computations for the present study have been conducted using ANSYS FLUENT 14.5. The solid energy equation is solved as a user-defined scalar equation, while data related to energy flux vectors and entropy generation are obtained using user-defined functions. 相似文献
80.