Surajit Biswas

A cyanide selective off–on fluorescent chemosensor with in vivo imaging in 100% water: solid probe preferred over in situ generation

A nontoxic fluorescent chemosensor [Cu(BP)HMB]2(ClO4)2 (1) synthesized in solid phase, exhibits unprecedented selectivity and sensitivity over the allied in situ complexes to perform fluorescence in “turn-off–on” mode for sensing cyanide in 100% aqueous medium under physiological conditions and for in vivo imaging using the nematode C. elegans. Below μM detection limit, instantaneous and excellent ratiometric responses are also beneficial to detect trace amounts of anthropogenic or biogenic cyanide.

Copper(II) induced oxidative modification and complexation of a schiff base ligand: synthesis, crystal structure, catalytic oxidation of aromatic hydrocarbons and DFT calculation

A mononuclear square planar complex [CuII(Lf)] (1) was synthesized and structurally characterized by single crystal X-ray diffraction studies. Though we have started with the Schiff base H2La with two –CH2OH groups for complexation with Cu2+, the final product appears to have two formyl groups where two carbinols were oxidized during the course of the reaction with Cu2+. It opens up the possibility of using this complex as a precursor for condensation with suitable amines to give symmetric/asymmetric cyclic/acyclic Schiff base complexes. Systematic studies on catalytic oxidation of aromatic hydrocarbons like toluene and xylenes by an environmentally benign oxidant, H2O2 in the presence of 1 as a catalyst reveals that it is an efficient catalyst leading to the formation of the corresponding alcohol as the major product with TON ∼300 and alcohol selectivity of ∼72%.

Mononuclear manganese(III) complexes of bidentate NO donor Schiff base ligands: synthesis, structural characterization, magnetic and catecholase studies

We have synthesized four mononuclear manganese(III) complexes (1–4) of four closely related bidentate NO donor Schiff-base ligands, out of which three (2–4) were structurally characterized. Crystal structure determination reveals that all these complexes are in octahedral geometries. Magnetic studies have been carried out on complexes 2, 3 and 4 in the temperature range 2–300 K under a magnetic field of 0.1 T which yielded negative ZFS parameters of −2.96, –3.51 and −3.72 cm−1 respectively. The catecholase activities of complexes 1–4 have been investigated following the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) with molecular oxygen in DCM at 25 °C, which were found to follow the Michalis–Menton type relation giving the highest TON (Kcat) for the so far reported Mn(III) complexes.

The first crystallographic observation of up to the third hydration layer of Cu(II) ion in an unusual ‘water-cation layer’ templated by an Anderson polyoxometallate

This constitutes the first crystallographic observation of hydrated Cu(II) ion retaining up to its third hydration layer which, along with the chair form water hexamer, builds up a unique water-cation layer. Moreover, an unprecedented supramolecular honeycomb network of [Cu(phen)3]2+ units templated by Anderson polyoxometallate units occupy the intervening spaces between successive water layers. Complex 1 is a rare example of parallel interpenetration of a 2D π–π network and a 3D pillar-layered hydrogen bonded network.

Structural, Spectroscopic, Magnetic, and Thermal Characterizations of a Magnetite Ore from the Nagaland Region, India

An Indian magnetite ore from the Nagaland region was characterized by powder X-ray diffraction, spectroscopies (ultraviolet-visible and Raman), high temperature magnetization and thermal analysis. A Rietveld refinement of the diffraction data revealed that the principal phase present in the sample is magnetite with partial substitution of Fe with Mg (mainly) and Cr, leading to the chemical formula of MgCr0.2Fe1.8O4. The UV-visible spectra of the sample in MeCN solution showed three distinct peaks. The lower region bands are due to metal-oxygen charge transitions and the other band is for d-d transition of iron. Raman spectral study at room temperature gave four characteristics bands of magnetite. The sample underwent a magnetic transition at high temperature and the thermomagnetization curve shows hysteresis during cooling cycle which indicates the possibility of first order structural transition at high temperature. The thermal property of the concentrate was studied by differential scanning calorimetric technique.