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31.
In aqueous solution ruthenium trichloride reacted with picolinic acid (Hpic) in the presence of a base to afford [Ru(pic)3]. In solution it shows intense ligand-to-metal charge transfer transitions near 310 and 370 nm, together with a low-intensity absorption near 2000 nm. [Ru(pic)3] is one-electron paramagnetic and shows a rhombic ESR spectrum in 1:1 dimethylsulphoxide-methanol solution at 77 K. The distortions from octahedral symmetry have been calculated by ESR data analysis. The axial distortion is larger than the rhombic one. In acetonitrile solution it shows a reversible ruthenium(III)-ruthenium(II) reduction at −0.09 V vs. SCE and a reversible ruthenium(III)-ruthenium(IV) oxidation at 1.52 V vs. SCE. Chemical or electrochemical reduction of [RuIII(pic)3] gives [RuII(pic)3]−, which in solution shows intense MLCT transitions near 360, 410 and 490 nm, and is converted back to [Ru(pic)3] by exposure to air. Reaction of [Ru(pic)3] with 8-quinolinol (HQ) in dimethylsulphoxide solution affords [RuQ3]. [Ru(bpy)(pic)2] (bpy = 2,2′-bipyridine) has been prepared by the reaction of Hpic with [Ru(bpy)(acac)2]Cl (acac = acetylacetonate ion) in ethyleneglycol. It is diamagnetic and in solution shows intense MLCT transitions near 370, 410 and 530 nm. In acetonitrile solution it shows a reversible ruthenium(II)-ruthernium(III) oxidation at 0.44 V vs. SCE and a reversible one-electron reduction of bpy at − 1.64V vs. SCE. 相似文献
32.
The structural features of quinone ligands are diagnostic of charge. The o-benzoquinone, radical semiquinonate, and catecholate electronic forms have C-O bond lengths and a pattern of ring C-C bond lengths that point to a specific mode of coordination. This correlation between ligand charge and structure has been extended to iminoquinone and iminothioquinone ligands, giving a charge-localized view of electronic structure for complexes of redox-active metal ions. The radical semiquinonate form of these ligands has been found to be a surprisingly common mode of coordination; however, the paramagnetic character of the radical ligand is often obscured in complexes containing paramagnetic metal ions. In this report, diamagnetic iminosemiquinonate (isq) and iminothiosemiquinonate (itsq) complexes of ls-d(5) Ru(III) with related complexes of osmium are reported. With osmium, the Os(IV)-amidophenolate (ap) redox isomer is formed. Electrochemical and spectral properties are described for Ru(PPh(3))(2)(isq)Cl(2), Ru(PPh(3))(2)(itsq)Cl(2), Os(PPh(3))(2)(ap)Br(2), Os(PPh(3))(2)(atp)Br(2), and Os(PPh(3))(2)(ap)H(2). Crystallographic characterization of Ru(PPh(3))(2)(isq)Cl(2), Ru(PPh(3))(2)(itsq)Cl(2), and Os(PPh(3))(2)(ap)H(2) was used to assign charge distributions. 相似文献
33.
We have studied the effect of shape of an amphiphilic molecule on micellization properties by carrying out stochastic molecular dynamics simulation on a bead-spring model of amphiphiles for several sizes of hydrophilic head group with a fixed hydrophobic tail length. Our studies show that the effect of geometry of an amphiphile on shape and cluster distribution of micelles is significant. We find the critical micelle concentration increases with the increasing size of the hydrophilic head. We demonstrate that the onset of micellization is accompanied by (i) a peak in the specific heat as found earlier in the simulation studies of lattice models, and (ii) a peak in the characteristic relaxation time of the cluster autocorrelation function. Amphiphiles with larger hydrophilic head form smaller micelles with sharper cluster distribution. Our studies are relevant to the controlled synthesis of nanostructures of desired shapes and sizes using self-assembling properties of amphiphiles. 相似文献
34.
A. Bhattacharya 《Journal of Thermal Analysis and Calorimetry》1997,49(3):1365-1371
Aesthetic and utilitarian properties of traditional ceramic wares as well as engineering properties of modern advanced ceramics are attained by maintaining an optimum temperature-time-atmosphere relationship, called firing schedule, in the kiln. The contribution of modern thermal analysis (TA) techniques such as TG/DTG, TG/EGA, TG/MS, DTA, DSC, TDA, etc. in 1) optimizing production steps by raw material quality control, by studying binder burn out, product densification, 2) in simulating appropriate preheating, firing and cooling schedules as well as 3) in developing shorter firing cycles has been extensively reported in recent literature. The paper will first discuss theoretical curves and energy required for ceramic firing and present from the literature selected examples of applications of thermal analysis in ceramic technology. 相似文献
35.
Gupta P Das A Basuli F Castineiras A Sheldrick WS Mayer-Figge H Bhattacharya S 《Inorganic chemistry》2005,44(6):2081-2088
Reaction of chloranilic acid (H2ca) with [Os(bpy)2 Br2] (bpy = 2,2'-bipyridine) affords a dinuclear complex of type [{Os(bpy)2}2 (ca)]2+, isolated as the perchlorate salt. A similar reaction of H2ca with [Os(PPh3)2 (pap)Br2] (pap = 2-(phenylazo)pyridine) affords a dinuclear complex of type [{Os(PPh3)2 (pap)}2 (ca)]2+ (isolated as the perchlorate salt) and a mononuclear complex of type [Os(PPh3)2 (pap)(ca)]. Reaction of H2ca with [Os(PPh3)2(CO)2(HCOO)2] gives a dinuclear complex of type [{Os(PPh3)2(CO)2}2 (r-ca)], where r-ca is the two electron reduced form of the chloranilate ligand. The structures of the [{Os(PPh3)2 (pap)}2 (ca)](ClO4)2, [Os(PPh3)2 (pap)(ca)], and [{Os(PPh3)2(CO)2}2 (r-ca)] complexes have been determined by X-ray crystallography. In the [{Os(bpy)2}2 (ca)]2+ and [{Os(PPh3)2 (pap)}2 (ca)]2+ complexes, the chloranilate dianion is serving as a tetradentate bridging ligand. In the [Os(PPh3)2 (pap)(ca)] complex, the chloranilate dianion is serving as a bidentate chelating ligand. In the [{Os(PPh3)2(CO)2}2 (r-ca)] complex, the reduced form of the chloranilate ligand (r-ca(4-)) is serving as a tetradentate bridging ligand. All the four complexes are diamagnetic and show intense metal-to-ligand charge-transfer transitions in the visible region. The [Os(PPh3)2 (pap)(ca)] complex shows an Os(II)-Os(III) oxidation, followed by an Os(III)-Os(IV) oxidation on the positive side of a standard calomel electrode. The three dinuclear complexes show two successive oxidations on the positive side of SCE. The mixed-valent Os(II)-Os(III) species have been generated in the case of the two chloranilate-bridged complexes by coulometric oxidation of the homovalent Os(II)-Os(II) species. The mixed-valent Os(II)-Os(III) species show intense intervalence charge-transfer transitions in the near-IR region. 相似文献
36.
37.
On the functional central limit theorem and the law of the iterated logarithm for Markov processes 总被引:2,自引:0,他引:2
R. N. Bhattacharya 《Probability Theory and Related Fields》1982,60(2):185-201
Summary Let X
tt0 be an ergodic stationary Markov process on a state space S. If  is its infinitesimal generator on L
2(S, dm), where m is the invariant probability measure, then it is shown that for all f in the range of
} } 0)$$
" align="middle" border="0">
converges in distribution to the Wiener measure with zero drift and variance parameter
2 =–2f, g=–2Âg, g where g is some element in the domain of  such that Âg=f (Theorem 2.1). Positivity of
2 is proved for nonconstant f under fairly general conditions, and the range of  is shown to be dense in 1. A functional law of the iterated logarithm is proved when the (2+)th moment of f in the range of  is finite for some >0 (Theorem 2.7(a)). Under the additional condition of convergence in norm of the transition probability p(t, x, d y) to m(dy) as t , for each x, the above results hold when the process starts away from equilibrium (Theorems 2.6, 2.7 (b)). Applications to diffusions are discussed in some detail.This research was partially supported by NSF Grants MCS 79-03004, CME 8004499 相似文献
38.
Asish K Bhattacharya Mahesh PalDharam C Jain Bhawani S JoshiRaja Roy Urszula RychlewskaRam P Sharma 《Tetrahedron》2003,59(16):2871-2876
Absolute stereochemistry of dihydroarteannuin B 5 obtained by the reduction of arteannuin B 3 with Ni2B, NaBH4 or CdCl2-Mg-MeOH-H2O has been established by 2D NMR and single crystal X-ray diffraction studies. Some experiments aimed at the synthesis of dihydrodeoxyarteannuin B [C-4, 5 double bond isomer of 11] are also discussed. 相似文献
39.
Immobilization of Mercuric reductase from aPseudomonas putida strain on different activated carriers
F. B. Anspach M. Huckel M. Brunke H. SChÜTte W. D. Deckwer 《Applied biochemistry and biotechnology》1994,44(2):135-150
Mercuric reductase was isolated fromPseudomonas putida KT2442::mer-73 and immobilized on Chromatographic carriers activated by various methods. The immobilization methods for covalent coupling were compared with regard to preservation of enzymatic activity and coupling yields. Highest yields were obtained with carriers bearing the most reactive functional groups. Best results were achieved with tresyl chloride-activated carriers. The optimum binding conditions were found at pH 8. Application of the immobilized mercuric reductase for continuous treatment of Hg(II)-containing water was examined in a fixed bed reactor. Space-time yields up to 510 nmol/min-mL were attained. The kinetics of immobilized enzyme systems were not diffusion-controlled. 相似文献
40.
Sumanta Bhattacharya Sandip K. Nayak Subrata Chattopadhyay Manas Banerjee 《Journal of solution chemistry》2006,35(4):485-506
Supramolecular complexes of [60]- and [70]fullerenes with various meso-tetraphenylporphyrins in toluene solutions have been studied by electronic absorption spectroscopy. Charge transfer (CT) absorption bands are observed in the visible region. Vertical ionization potentials (I
D
V) of the meso-tetraphenylporphyrins are reported from a study of EDA interaction of these porphyrins with a number of electron acceptors like o-chloranil, p-chloranil, 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) and vitamin K. The dependence of the CT transition energy on the donor ionization potential has been utilized to estimate the vertical electron affinities (E
A
V) of [60]- and [70]fullerenes in solution. The value of E
A
V for [60]fullerene is found to be 0.10 eV lower in magnitude than that of [70]fullerene. We have extracted degrees of CT, and oscillator and transition dipole strengths of the fullerenes/meso-tetraphenylporphyrins complexes. The experimental results show that the CT complexes studied here have a neutral character in their ground states. Electronic coupling elements have been determined for fullerene/meso-tetraphenylporphyrin complexes. Values of the solvent reorganization energy indicate that the electron transfer process takes place at a faster rate in the case of [70]fullerene/meso-tetraphenylporphyrin complexes. 相似文献