Rahul Bhattacharya

Bio: Rahul Bhattacharya is an academic researcher from University of Calcutta. The author has contributed to research in topics: Covariate & Categorical variable. The author has an hindex of 6, co-authored 36 publications receiving 215 citations.

Synthesis, characterisation and X-ray crystal structure of copper(II) complexes with unsymmetrical tetradentate schiff base ligands: First evidence of Cu(II) catalysed rearrangement of unsymmetrical to symmetrical complex

Abstract: The mononuclear copper(II) complexes, [CuL1](ClO4) (1), and [CuL2](ClO4) (2) with unsymmetrical quadridentate Schiff base ligands derived from the 1:1:1 condensation of 2,4-pentanedione, pyridine-2-carboxaldehyde and 1,2-ethanediamine (HL1) or 1,3-propanediamine (HL2) have been prepared and characterised. Complex 2 undergoes Cu(II)/H+ catalysed rearrangement to [CuL3](ClO4)2 (3) where L3 is a symmetrical tetradentate Schiff base involving 1,3-propanediamine and pyridine-2-carboxaldehyde. Structures of all the three compounds have been verified by single crystal X-ray analysis. The geometry around Cu(II) is square-planar in 1 and 2 whereas that in 3 is distorted octahedral with two axially coordinated perchlorate ions.

Synthesis, crystal structure and thermochromism of benzimidazolium tetrachlorocuprate: (C7H7N2)2[CuCl4]

Abstract: The synthesis and crystal structure of thermochromic, yellow benzimidazolium tetrachlorocuprate(II), (C7H7N2)2CuCl4 (1), have been reported. The compound crystallizes in the C 2/c space group and contains discrete tetrahedral CuCl4 2� species. It absorbs one molecule of water from humid atmosphere at room temperature to produce a hydrated green form, (C7H7N2)2CuCl4/H2O, which upon heating loses the water molecule in two steps to form the anhydrous yellow compound 1. The role of the water molecule on the solid state, yellow v/green thermochromic transformation is discussed. # 2002 Elsevier Science Ltd. All rights reserved.

Synthesis and crystal structure of bis(2-methylbenzimidazolium) tetrahalocuprate (II)

Abstract: The crystal structures of 2-methylbenzimidazolium tetrahalocuprates (H2-mebz)2[CuX4] (X = Cl and Br) have been detemined. The chloride salt is monoclinic, P21/c, with a = 8.540(2) A, b = 16.591(2) A, c = 14.303(3) A, and β = 98.69(2)°. The bromide salt is also monoclinic, P21/c, with a = 8.316(3) A, b = 17.436(3) A, c = 14.747(3) A, and β = 98.82(3)°. Both the compounds contain discrete distorted tetrahedral CuX42− anions and almost planar 2-methylbenzimidazolium cations. In the chloride salt, three chloride ions are involved in hydrogen bonding instead of two bromide ions in the bromide salt.

Synthesis, Crystal Structure, Thermal Analysis and Magnetic Behavior of a Novel One‐Dimensional Polymeric Pyridinium Chlorocuprate(II): (Hpy)2[Cu3Cl8(H2O)2]

Abstract: A one-dimensional polymeric pyridinium chlorocuprate (HPy)2[Cu3Cl8(H2O)2], an intermediate between (HPy)CuCl3 and CuCl2·2H2O, has been synthesized and characterized by X-ray analysis [monoclinic, P21/c, a = 7.8950(10), b = 14.144(2), c = 9.921(10) A, β = 99.20(2)°]. The structure contains [Cu3Cl8(H2O)2]n2n− chains in which both square-pyramidal and octahedral CuII exist. The chains are composed of linked [Cu2Cl6]2− dimers and CuCl2(H2O)2 monomeric units. On being heated in the solid state the compound undergoes dehydration followed by dehydrohalogenation to produce a pyridine complex of CuII: [Cu3Py2Cl6]. Other compounds, (HPy)2[CuCl4], CuPyCl2 and CuPy2Cl2, also produce [Cu3Py2Cl6] as an intermediate on thermal analysis. Magnetic studies reveal ferromagnetic coupling within the chains with an intradimer exchange coupling of 12.1 cm−1 and a dimer-monomer exchange coupling of 1.34 cm−1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

On a class of optimal covariate-adjusted response adaptive designs for survival outcomes.

Abstract: A class of optimal covariate-adjusted response adaptive procedures is developed for phase III clinical trials when the treatment response is a survival time and there is random censoring. The basic aim is to develop an allocation design by combining the ethical aspects with statistical precision in a reasonable way under the presence of covariate information. Considering minimisation of total hazards as the ethical requirement, the proposed procedure is assessed in terms of the assignment to the better treatment and the efficiency (i.e. power) to detect a small departure in treatment effectiveness. The applicability of the proposed methodology is also illustrated using a real data set.

Univariate Discrete Distributions

Abstract: Here are two books on a topic new to Technometrics: statistical and mathematical demography. The first author of Applied Mathematical Demography wrote the first two editions of this book alone. The second edition was published in 1985. Professor Keyfritz noted in the Preface (p. vii) that at age 90 he had no interest in doing another edition; however, the publisher encouraged him to find a coauthor. The result is an additional focus for the book in the world of biology that makes it much more relevant for the sciences. The book is now part of the publisher’s series on Statistics for Biology and Health. Much of it, of course, focuses on the many aspects of human populations. The new material focuses on mature population models, the particular focus of the new author (see, e.g., Caswell 2000). As one might expect from a book that was originally written in the 1970s, it does not include a lot of information on statistical computing. The new book by Alho and Spencer is focused on putting a better emphasis on statistics in the discipline of demography (Preface, p. vii). It is part of the publisher’s Series in Statistics. The authors are both statisticians, so the focus is on statistics as used for demographic problems. The authors are targeting human applications, so their perspective on science does not extend any further than epidemiology. The book actually strikes a good balance between statistical tools and demographic applications. The authors use the first two chapters to teach statisticians about the concepts of demography. The next four chapters are very similar to the statistics content found in introductory books on survival analysis, such as the recent book by Kleinbaum and Klein (2005), reported by Ziegel (2006). The next three chapters are focused on various aspects of forecasting demographic rates. The book concludes with chapters focusing on three areas of applications: errors in census numbers, financial applications, and small-area estimates.

Multidentate unsymmetrically-substituted Schiff bases and their metal complexes: Synthesis, functional materials properties, and applications to catalysis

Abstract: This review focuses on the recent developments of unsymmetrically-substituted multidentate Schiff bases whose steric and electronic characteristics are easily manipulated by selecting suitable condensing aldehydes or ketones and primary amines, and on their metal complexes. After a brief historical introduction, this manuscript is divided in three main sections. In the two first parts, the synthesis, reactivity, functions, and properties of tridentate Schiff base precursors and of quadridentate Schiff base metal complexes, respectively, are discussed through a literature survey including examples of research from the authors’ groups. More specifically, the second section is formed of seven subsections with the synthesis of unsymmetrically-substituted tetradentate Schiff bases and their transition metal (V, Mn, Fe, Co, Ni, Cu, Zn, Ru, Pd, Pt) and uranyl complexes. Emphasis is given to our research work based on ferrocenyl-containing tri- and tetradentate unsymmetrically-substituted Schiff base complexes of Ni(II) and Cu(II) starting from variously substituted ferrocenyl-β-diketones. The unsymmetrically-substituted Schiff base complexes present a wide range of remarkable properties that are also summarized in this section, including structural, biocidal, magnetic, and second-order nonlinear optical properties. The third section is devoted to the catalytic activity of Schiff base metal complexes that is discussed through thirteen major organic reactions, including copper-catalyzed azide–alkyne cycloaddition (CuAAC), Henry and nitro-Mannich reactions, hydrosilylation of ketones, aldol, cyclopropanation and epoxidation reactions, among others.

Nickel(II) and copper(II) complexes of tetradentate unsymmetrical Schiff base ligands: First evidence of positional isomerism in such system

Abstract: The 1:1 condensation of 2,4-pentanedione and 1,2-diaminopropane gives a mixture two positional isomers of tridentate mono-condensed product 7-amino-4-methyl-5-aza-3-octene-2-one (HAMAO) and 7-amino-4,6-dimethyl-5-aza-3-heptene-2-one (HADAH) that reacted readily with Ni(II) thiocyanate to yield exclusively a single product, [Ni(AMAO)NCS] (1) in which the methyl substituent of diamine is ‘remote’ from the imino nitrogen. The mixture of terdentate ligands has been used for further condensation with pyridine-2-carboxaldehyde or 2-acetylpyridine to obtain the unsymmetrical tetradentate Schiff base ligands. The tetradentate ligands formed by the condensation of it and pyridine-2-carboxaldehyde readily yielded complexes with Cu(II) and Ni(II) (2 and 3, respectively). Crystal structure analysis shows that in 2 the condensation site of the diamine with 2,4-pentanedione is the same as in 1 but that in 3 is different (the methyl group of the diamine is located in the vicinity of 2,4-pentanedione), i.e., the tetradentate ligand is in two different isomeric forms in complexes 2 and 3. Another tetradentate ligand, obtained by the condensation of the tridentate ligands and 2-acetylpyridine yielded a Ni(II) complex (4) where the methyl group is in the vicinity of 2,4-pentanedione as in 3. The isomerization in the Ni(II) complexes has been studied by NMR spectroscopy.