Publications by authors named "Tamal K Sen"

Main group metal based catalysis has been considered to be a cost-effective alternative way to the transition metal based catalysis, due to the high abundance of main group metals in the Earth's crust. Among the main group metals, aluminum is the most abundant (7-8%) in the Earth's crust, making the development of aluminum based catalysts very attractive. So far, aluminum based compounds have been popularly used as Lewis acids in a variety of organic reactions, but chemical transformation demanding a redox based process has never utilized an Al(III) complex as a catalyst.

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The phenalenyl unit has played intriguing role in different fields of research spanning from chemistry, material chemistry to device physics acting as key electronic reservoir which has not only led to the best organic single component conductor but also created the spin memory device of next generation. Now we show the non-innocent behaviour of phenalenyl unit in modulating the catalytic behaviour in a homogeneous organic transformation. The present study establishes that the cationic state of phenalenyl unit can act as an organic Lewis acceptor unit to influence the catalytic outcome of intermolecular hydroamination reaction of carbodiimides.

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Abnormal N-heterocyclic carbene (aNHC) adducts of zinc(II) (1) and aluminum(III) (2) were synthesized. The compounds were characterized by NMR spectroscopy and elemental analysis. The solid state structures of these complexes (1 and 2) were determined by single crystal X-ray study.

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Two new water-soluble hetero- and homometallic tetranuclear clusters, Na4[Cu2Zn2(ccdp)2(μ-OH)2]·CH3OH·6H2O (1) and K3[Cu4(ccdp)2(μ-OH)(μ-OH2)]·14H2O (2), have been synthesized in methanol-water at room temperature by exploiting the flexibility, chelating ability, and bridging potential of a carboxylate-rich dinucleating ligand, N,N'-bis(2-carboxybenzomethyl)-N,N'-bis(carboxymethyl)-1,3 diaminopropan-2-ol (H5ccdp). Complex 1 is obtained through the self-assembly of two monoanionic [CuZn(ccdp)](-)fragments, which are, in turn, exclusively bridged by two μ-OH(-)groups. Similarly, complex 2 is formed through the self-assembly of two monoanionic [Cu2(ccdp)](-) species exclusively bridged by one μ-OH(-) and one μ-OH2 groups.

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The use of molecular spin state as a quantum of information for storage, sensing and computing has generated considerable interest in the context of next-generation data storage and communication devices, opening avenues for developing multifunctional molecular spintronics. Such ideas have been researched extensively, using single-molecule magnets and molecules with a metal ion or nitrogen vacancy as localized spin-carrying centres for storage and for realizing logic operations. However, the electronic coupling between the spin centres of these molecules is rather weak, which makes construction of quantum memory registers a challenging task.

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A series of zinc complexes (1-6) supported by substituted phenalenyl ligands was synthesized by reacting the phenalenyl ligands with diethyl zinc under ethane evolution. The solid state structures of these complexes (1-6) were determined by single crystal X-ray crystallography. Furthermore, the organozinc complexes (4-6) were tested for the polymerization of cyclic esters as efficient catalysts for the ring-opening polymerization of ε-caprolactone (ε-CL) and rac-lactide (rac-LA) in the presence of benzyl alcohol (BnOH) as initiator.

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Herein, we report the synthesis and characterization of two organozinc complexes that contain symmetrical phenalenyl (PLY)-based N,N-ligands. The reactions of phenalenyl-based ligands with ZnMe(2) led to the formation of organozinc complexes [N(Me),N(Me)-PLY]ZnMe (1) and [N(iPr),N(iPr)-PLY]ZnMe (2) under the evolution of methane. Both complexes (1 and 2) were characterized by NMR spectroscopy and elemental analysis.

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Palladium complexes bearing abnormal N-heterocyclic carbene were used as catalysts in Suzuki-Miyaura cross coupling of aryl chlorides at 25 °C. The catalyst remained active for 10 successive catalytic runs and can activate 4-chlorotoluene at 25 °C with 0.01 mol% catalyst loading resulting in a TON of 9500 within 6 h.

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The recently isolated abnormal N-heterocyclic carbene (aNHC) has been established as an efficient organocatalyst in ring opening polymerization of three different cyclic esters rac-lactide (rac-LA), ε-caprolactone (ε-CL), and δ-valerolactone (δ-VL). Preliminary DFT calculations indicate that aNHC can be a better organocatalyst than the corresponding nNHC counterpart.

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