http://nopr.niscpr.res.in/handle/123456789/56195 2026-10-11T14:02:46Z http://nopr.niscpr.res.in/handle/123456789/56205 Title: Epoxidation and catechol oxidation catalytic processes promoted by manganese(III) complexes of salen-type ligands Authors: Guha, Averi; Zangrando, Ennio; Chandra, Arpita Abstract: Four new mononuclear manganese(III) complexes namely <strong>1</strong>, <strong>2</strong>,<strong> 3 </strong>and <strong>4 </strong>of salen-type ligands H₂L¹-H₂L⁴ (ligands were obtained <em>in situ</em> via Schiff-base condensation of 2-formyl-6-hydroxymethyl-4-methylphenol and amines cyclohexane-1,2-diamine, 2-methylpropane-1,2-diamine, propane-1,2-diamine and ethane-1,2-diamine, respectively) have been synthesised and characterised by routine physicochemical techniques. <strong>1</strong> is further characterised by X-ray single crystal structure analysis. Catalytic efficiencies of the complexes as epoxidation catalysts (substrates: styrene and (<em>E</em>)-stilbene; terminal oxidants: PhIO/NaOCl; solvent: MeCN /dicholorometane) and as catalysts for oxidation of catachol (substrates: 3,5-di-<em>tert</em>-butylcatechol (3,5-DTBC); solvent: methanol) have been evaluated. In both cases the catalytic efficiency increases on going from <strong>4-1</strong> although the actual mechanisms in those two catalytic reactions are completely different. However, the observations have been rationalized on the basis of steric and electronic factors exerted by the alkyl substituents present on the imine back-bone of the salen-type ligands. This study also verifies that there is at least another active epoxidizing species, [Cl–O–Mn(III)(salen)X] in addition to the discrete Mn(V)=O(salen) species in epoxidation of olefins depending upon the terminal oxidants employed. Page(s): 169-176 2021-02-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/56204 Title: Revisiting the reactivity of Ru3(CO)12 with PhC≡CPh (diphenylacetylene)-new findings of a thermic effect towards higher nuclearity Authors: Bhowmik, Mihir L; Abedin, Tareque S M; Kabir, Shariff E Abstract: In this paper, we report tri- and tetranuclear ruthenium carbonyl compounds containing PhC≡CPh ligand showing μ₃-η², μ₃-η⁴, μ₄-η²coordination modes. A one-pot reaction between [Ru₃(CO)₁₂] and PhC≡CPh in THF (tetrahydrofuran) at 66 °C has given the new trinuclear compound [Ru₃(CO)₆(μ-CO)₂(μ₃-η⁴-C₄Ph₄)] (<strong>2</strong>) in 30% yield together with the previously reported [Ru₃(CO)₈(μ₃-η²-C₂Ph₂)₂] (<strong>1</strong>) in 25% yield. Compound <strong>1</strong> converts to <strong>2</strong> under refluxing condition in THF. A similar reaction involving [Ru₃(CO)₁₂] with PhC≡CPh in refluxing benzene (80 ^°C) afforded previously reported <em>closo</em>-tetraruthenium compounds [Ru₄(CO)₁₂(μ₄-η²-C₂Ph₂)] (<strong>3</strong>) and [Ru₄(CO)₁₀(μ-CO)(μ₄-η²-C₂Ph₂)₂] (<strong>4</strong>) in 25 and 16% yields, respectively, along with <strong>2</strong> in 20% yield. Compounds <strong>1</strong>, <strong>2</strong> and <strong>4</strong> have been characterized by single-crystal X-ray diffraction analysis in addition to IR and ¹H NMR spectroscopic methods. Page(s): 177-184 2021-02-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/56203 Title: Synthesis, spectral and structural characterization of organic ammonium paratungstates Authors: Morajkar, Sudesh M; Srinivasan, Bikshandarkoil R Abstract: Dissolution of tungsten(VI) oxide hydrate (WO₃·H₂O) in aqueous organic amine (RNH₂ where R = methyl or ethyl, or <em>n</em>-propyl or isopropyl or <em>n</em>-butyl or <em>t</em>-butyl etc.) results in the formation of the tetrahedral tetraoxidotungstate(VI) species in solution. Slow evaporation of the reaction mixture to isolate the tetraoxidotungstates charge balanced by organic ammonium cations afforded organic ammonium paratungstates having formula (RNH₃)₁₀[H₂W₁₂O₄₂]·xH₂O. The presence of (WO₄)^2- species in solution and the [H₂W₁₂O₄₂]¹⁰^- unit in the solid product is confirmed by the characteristic Raman spectra. In this paper, we report on the synthesis, Raman spectra, crystal structures and properties of two organic ammonium paratungstates <em>viz</em>. (MeNH₃)₁₀[H₂W₁₂O₄₂]·12H₂O <strong>1</strong> (MeNH₂ = methylamine) and (EtNH₃)₁₀[H₂W₁₂O₄₂]·4H₂O <strong>2 (</strong>EtNH₂ = ethylamine). Thermal decomposition of <strong>1</strong> or <strong>2</strong> at 800 °C results in the formation of monoclinic form of tungsten trioxide WO₃. A comparative study of several paratungstates is described. Page(s): 185-195 2021-02-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/56202 Title: Synthesis and spectroscopic calf thymus deoxyribonucleic acid binding investigations of luteolin – zinc(II) complex Authors: Zhang, Shufang; Sun, Xuejun; Tian, Laijin Abstract: A luteolin–zinc(II) (lut–Zn) complex has been synthesized by the reaction of luteolin with copper acetate in alcohol. The binding mode of lut–Zn with calf thymus deoxyribonucleic acid (ctDNA) is studied by different spectroscopic methods in pH 7.4 tris(hydroxymethyl)aminomethane–HCl (Tris–HCl) buffer solution. Ultraviolet (UV)–visible absorption spectrophotometry and fluorescence spectroscopy as well as viscosity measurements have proved the formation of lut–Zn–ctDNA complex. Binding constant (K_a) of lut–Zn–ctDNA complex is 4.29 × 10⁴ L mol^-1 (310 K). Fluorophotometry measurements has proved that the quenching mechanism of fluorescence of acridine orange (AO)–ctDNA by lut–Zn is static quenching. The thermodynamic parameters entropy change (ΔS), enthalpy change (ΔH) and Gibbs free energy (ΔG) of binding reaction are calculated to be -20.87 J K^-1 mol^-1, -3.39 × 10⁴J mol^-1and -2.74 × 10⁴ J mol^-1 at 310 K, respectively. Negative values of ΔH and ΔS have indicated that there are hydrogen bonds and van der Waals forces in the binding reaction of lut–Zn with ctDNA. The fluorescence results and UV–visible absorption together have revealed that the interaction mode of lut–Zn to ctDNA is an intercalation mode. This conclusion is further confirmed by viscosity measurements. Page(s): 196-201 2021-02-01T00:00:00Z