• Munirathinam Nethaji

      Articles written in Journal of Chemical Sciences

    • Organometallic chemistry of chiral diphosphazane ligands: Synthesis and structural characterisation

      Kannan Raghuraman Swadhin K Mandal T S Venkatakrishnan Setharampattu S Krishnamurthy Munirathinam Nethaji

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      The diphosphazane ligands of the type, (C20H12O2)PN(R)P(E)Y2 (R = CHMe2 or (S)-*CHMePh; E = lone pair or S; Y2 = O2C20H12 or Y = OC6H5 or OC6H4Me-4 or OC6H4OMe-4 or OC6H4But-4 or C6H5) bearing axially chiral 1,1'-binaphthyl-2,2′-dioxy moiety have been synthesised. The structure and absolute configuration of a diastereomeric palladium complex, [PdCl2{ηsu2}-((O2C20H12)PN((S)-*CHMePh)PPh2] has been determined by X-ray crystallography. The reactions of [CpRu(PPh3)2Cl] with various symmetrical and unsymmetrical diphosphazanes of the type, X2PN(R)PYY′ (R = CHMe2 or (S)-*CHMePh; X = C6H5 or X2 = O2C20H12; Y=Y′= C6H5 or Y = C6H5, Y′ = OC6H4Me-4 or OC6H3Me2-3,5 or N2C3HMe2-3,5) yield several diastereomeric neutral or cationic half-sandwich ruthenium complexes which contain a stereogenic metal center. In one case, the absolute configuration of a trichiral ruthenium complex, viz. [Cp*Ruη2-Ph2PN((S)-*CHMePh)*PPh (N2C3HMe2-3,5)Cl] is established by X-ray diffraction. The reactions of Ru3(CO)12 with the diphosphazanes (C20H12O2)PN(R)PY2 (R = CHMe2orMe; Y2=O2C20H12or Y= OC6H5 or OC6H4Me-4 or OC6H4OMe-4 or OC6H4But-4 or C6H5) yield the triruthenium clusters [Ru3(CO)10{η-(O2C20H12)PN(R)PY2}], in which the diphosphazane ligand bridges two metal centres. Palladium allyl chemistry of some of these chiral ligands has been investigated. The structures of isomeric η3-allyl palladium complexes, [Pd(η3-l,3-R′2-C3H3){η2-(rac)-(02C20H12)PN(CHMe2)PY2}](PF6) (R′ = Me or Ph; Y = C6H5 or OC6H5) have been elucidated by high field two-dimensional NMR spectroscopic and X-ray crystallographic studies.

    • Effect of copper-sulphur bond on the DNA photo-cleavage activity of 2-(methylthio)ethylpyridine-2-carbaldimine copper(II) complexes

      Tarkeshwar Gupta Ashis K Patra Shanta Dhar Munirathinam Nethaji Akhil R Chakravarty

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      The binding and photo-induced DNA cleavage activity of a binary complex [CuL2](ClO4)2 (1) and the in situ generated ternary complexes [CuLB](ClO4)2 from 1 (B: 1,10-phenanthroline, phen, 2; dipyrido[3,2-d: 2′,3′-f]quinoxaline, dpq, 3) are studied, where L is a N2S-donor tridentate Schiff base 2- (methylthio)ethylpyridine-2-carbaldimine. Complex 1, structurally characterized by X-ray diffraction study, has six-coordinate meridional geometry showing CuN4S2 coordination. The Cu-N bond lengths are in the range of 1·968(3) to 2·158(4) Å. The Cu-S bond lengths of 2·599(2) and 2·705(2) Å are significantly long indicating weak covalent interaction between copper and sulphur atoms. The thiomethyl groups are cis to each other giving S-Cu-S angle of 75·82(5)°. The Cu-N(pyridyl) bond distances are longer than the Cu-N(imine) bonds. The complexes are redox active and display a quasi-reversible cyclic voltammetric response assignable to the Cu(II)/Cu(I) couple near 0·0 V vs SCE in DMF-Tris buffer (1: 4 v/v) using 0·1 M KCl as supporting electrolyte. Electronic spectra of the complexes show a d-d band in the range 630 to 700 nm in DMF along with higher energy charge transfer bands. While complex 1 is a poor binder to DNA, the ternary complexes show good DNA binding propensity. The photo-nuclease activity of 13 is studied using UV and visible wavelengths. The DNA cleavage activity at 365 nm follows the order: 3 > 2 > 1. The cleavage reaction involves the formation of singlet oxygen as the reactive species in a type-II process.

    • Tris(dithiocarboxylato)indium(III): Thermal studies and crystal structure of [In(S2Ctol)3]

      Shamik Ghoshal Nisha P Kushwah Manoj K Pal Vimal K Jain Munirathinam Nethaji

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      Tris(dithiocarboxylato)indium(III), [In{S2CAr}3] (Ar = phenyl or 𝑝-tolyl) have been synthesized and characterized. The molecular structure of [In(S2Ctol)3] established by single crystal X-ray diffraction revealed a distorted octahedral geometry with symmetrically chelating dithiocarboxylate groups. These complexes on thermolysis gave 𝛽-In2S3 which was characterized by XRD and EDX.

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