Suranjana Das

Supramolecular Lone Pair-π/π-π/π-Anion Assembly in a Mg(II)-Malonate-2-Aminopyridine-Nitrate Ternary System

The solid-state structure of an alkaline-earth metal complex reveals the formation of a remarkable supramolecular framework based on concurrent lone pair-pi, pi-pi, and pi-anion interactions whose stability has been investigated by density functional theory.

Mechanistic studies on the oxidation of ascorbic acid and hydroquinone by a {Mn4O6}4+ core in aqueous media.

Described in this work is the kinetics of oxidation of ascorbic acid and hydroquinone by a tetranuclear Mn(IV) oxidant, [Mn(4)(μ-O)(6)(bipy)(6)](4+) (1(4+), bipy =2,2(/)-bipyridine), in aqueous solution over a wide pH range 1.5-6.0. In particular, below pH 3.0, protonation on the oxo-bridge of 1(4+) results in the formation of [Mn(4)(μ-O)(5)(μ-OH)(bipy)(6)](5+) (1H(5+)) as an additional oxidant over 1(4+). Both ascorbic acid and ascorbate whereas only hydroquinone and none of its protolytic species were found to be reactive reducing agents in these reactions. Analysis of the rate data clearly established that the oxo-bridge protonated oxidant 1H(5+) is kinetically far more superior to 1(4+) in oxidizing ascorbic acid and hydroquinone. Rates of these reactions are substantially lowered in D(2)O-enriched media in comparison to that in H(2)O media. An initial one electron one proton transfer electroprotic rate step could be mechanistically conceived. DFT studies established that among the two sets of terminal and central Mn(IV) atoms in the tetranuclear oxidant, one of the two terminal Mn(IV) is reduced to Mn(III) at the rate step that we can intuitively predict considering the probable positive charge distribution on the Mn(IV) atoms.

Mechanistic studies on oxidation of nitrite by a {Mn3O4}4+ core in aqueous acidic media

[MnIV3(micro-O)4(phen)4(H2O)2]4+ (, phen=1,10-phenanthroline) equilibrates with its conjugate base [Mn3(micro-O)4(phen)4(H2O)(OH)]3+ in aqueous solution. Among the several synthetic multinuclear oxo- and/or carboxylato bridged manganese complexes known to date containing metal-bound water, to the best of our knowledge, only deprotonates (right harpoon over left harpoon+H+, pKa=4.00 (+/-0.15) at 25.0 degrees C, I=1.0 M, maintained with NaNO3) at physiological pH. An aqueous solution of quantitatively oxidises NIII (HNO2 and NO2-) to NO3- within pH 2.3-4.1, the end manganese state being MnII. Both and are reactive oxidants in the title redox. In contrast to a common observation that anions react quicker than their conjugate acids in reducing metal centred oxidants, HNO2 reacts faster than NO2- in reducing or . The observed rates of nitrite oxidation do not depend on the variation of 1,10-phenanthroline content of the solution indicating that the MnIV-bound phen ligands do not dissociate in solution under experimental conditions. Also, there was no kinetic evidence for any kind of pre-equilibrium replacement of MnIV-bound water by nitrite prior to electron transfer which indicates the substitution-inert nature of the MnIV-bound waters and the 1,10-phenanthroline ligands. The MnIV3 to MnII transition in the present observation proceeds through the intermediate generation of the spectrally characterised mixed-valent MnIIIMnIV dimer that quickly produces MnII. The reaction rates are substantially lowered when solvent H2O is replaced by D2O and a rate determining 1e, 1H+ electroprotic mechanism is proposed.

Performance of Phosphobacteria on Phosphorus Economy and Net Return in Different Potato Growing Region of India

Field experiments were conducted at eleven centers of All India Coordinated Research Project on Potato located in different agro-climatic zones to investigate the role of phosphobacteria in P economy in potato crop during 2005–06 and 2006–07. Six treatments consisting of combinations of different levels of P as well as phosphobacteria (PSB) used in the study showed significant effect on yield of potato. At Kalyani, Chhindwara, Kota, Patna, Hassan and Ooty, recommended dose of NK + 75% P + PSB was statistically at par with recommended dose of NPK in term of total yield. At Bhubaneshwar, Dholi, Hisar, Deesa and Modipuram, 75% of fertilizer P + PSB either had no significant effect on potato tuber yield or reduced the yield marginally in two years of experimentations. Net returns with recommended NPK or 75% P + PSB showed the best results at most of the centers. The per cent saving of fertilizer P, calculated using quadratic model, was maximum for Hassan (43%). In general, use of PSB saved around 20 to 25% P, depending upon agro-ecological situations and soil conditions. However, at Bhubaneshwar, Kota and Dholi the saving being very meager was not economical. The results clearly indicate the role of PSB in saving fertilizer P across different agro-climatic zones, However, it also came out very clearly that effectiveness of the PSB depends on agro-ecological situations and soil conditions.