Malay Dolai

A novel pyrene-2-(pyridin-2-ylmethylsulfanyl)ethylamine based turn-on dual sensor for Al3+: experimental and computational studies

A new pyrene based highly sensitive and selective Al3+ sensor, pyrene-2-(pyridin-2-ylmethylsulfanyl)-ethylamine (PP), was found to exhibit a turn-on fluorescence enhancement (FE) as high as 7.4 fold with Kd (2.55 ± 0.10) × 10−4 M and n = 1. This probe binds reversibly with Al3+ in the presence of H2EDTA2−, both under intra- and exctracellular conditions. LOD determined by 3σ methods was found to be 15 nM while LOQ = 52.8 nM. The tentative coordination environment in the Al3+–PP complex was delineated by DFT calculations both on the free ligand and complex. The TDDFT calculations reveal spectral features comparable to the experimental ones.

Water-stable manganese(IV) complex of a N2O4-donor non-Schiff-base ligand: synthesis, structure, and multifrequency high-field electron paramagnetic resonance studies.

A novel water-stable (t1/2 ∼ 6.8 days) mononuclear manganese(IV) complex of a hexacoordinating non-Schiff-base ligand (H4L) with N2O4-donor atoms has been synthesized and characterized crystallographically. High-frequency electron paramagnetic resonance experiments performed on a single crystal reveal a manganese(IV) ion with an S = 3/2 ground spin state that displays a large single-ion anisotropy, setting the record of mononuclear manganese(IV) complexes reported so far. In addition, spin-echo experiments reveal a spin-spin relaxation time T2 ∼ 500 ns.

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.

Hydrothermal synthesis of two supramolecular inorganic–organic hybrid phosphomolybdates based on Ni(II) and Co(II) ions: structural diversity and heterogeneous catalytic activities

Two new hybrid compounds based on phosphomolybdates, namely (NHEPH2)5[NiII(P4Mo6O31)2]·6H2O (1) and {(NHEPH2)2[CoII(H2O)6]}[P2Mo5O23]·2H2O (2) (NHEP = N-(2-hydroxyethyl)-piperazine), have been synthesized under hydrothermal conditions and characterized by elemental analyses, IR, TGA, single crystal X-ray diffraction and PXRD studies. In compound 1, Ni(II) is sandwiched between two {P4Mo6O31}6− clusters and the residual negative charges are neutralized by NHEPH22+. In compound 2, the [P2Mo5O23]6− ion exists as a discrete moiety and the negative charges are compensated by both [Co(H2O)6]2+ and NHEPH22+. The extensive hydrogen bonding involving the organic cations and water molecules yielded three-dimensional (3D) open framework structures in these systems. These phosphomolybdate based compounds showed good catalytic efficiency in heterogeneous oxidation of styrene in the presence of an environmentally benign oxidant, H2O2, under mild conditions.

σ-Aromaticity in dinuclear copper(II) complexes: Novel interaction between perchlorate anion and σ-aromatic [Cu2X2] (X = N or O) core

Two dinuclear Cu(II) complexes [Cu2(3,5-dimethyl-pyrazole)4(1,1-N3)2(ClO4)2] (1) and [Cu2(3,5-dimethyl-pyrazole)2(N-hydroxymethyl-3,5-dimethyl-pyrazole)2(ClO4)2] (2) with rhombus [Cu2X2] cores exhibit σ-aromaticity that unprecedentedly interact with two closely disposed coordinated perchlorate ions with interaction energies, −53 and −47 kJ mol−1 respectively.

Three novel mononuclear Mn(III)-based magnetic materials with square pyramidal versus octahedral geometries

A series of new manganese schiff base complexes have been prepared and characterized by single crystal X-ray diffraction studies, which showed that all the three complexes are mononuclear; 1 and 2 have square pyramidal geometry, whereas 3 has an octahedral geometry. Magnetic studies reveal that all these complexes exhibit (i) moderate frequency dependence of ac magnetic susceptibility at low temperature upon the application of a dc external field; (ii) significant magnetic anisotropy (D) and (iii) antiferromagnetic interaction that persist between the neighbouring molecules. Therefore, our systematic studies have shown the influence of electronic, geometric and packing effects of a new series of mononuclear manganese(III) complexes with axially elongated square pyramidal and octahedral geometries on the negative D values.