• Somnath Choubey

      Articles written in Journal of Chemical Sciences

    • Syntheses, molecular and crystalline architectures, and luminescence behaviour of terephthalate bridged heptacoordinated dinuclear lead(II) complexes containing a pentadentate N-donor Schiff base

      Subhasis Roy Somnath Choubey Sumitava Khan Kishalay Bhar Partha Mitra Barindra Kumar Ghosh

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      One-pot synthesis using a 2:2:1:2 molar ratio of Pb(OAc)2·3H2O, L, piperidinum terephthalate (ptp) and NaClO4/NH4PF6 at room temperature affords two dinuclear compounds of the type [Pb2(L)2(𝜇- tp)](ClO4/PF6)2 (1/2) [L=N,N'-(bis-(pyridin-2-yl)benzylidene)diethylenetriamine and tp = terephthalate dianion]. The compounds are characterized by microanalytical, spectroscopic, thermal and other physicochemical results. X-ray structural analyses of 1 and 2 reveal that each heptacoordinated lead(II) centre with a PbN5O2 chromophore are bound by five N atoms of L and connected through O atoms of a bis(bidentate) tp bridge. The arrangements of L and tp suggest a gap around the metal centre due to occupation of a stereo-active lone pair of electrons reflecting a hemidirected coordination around the metal centre. The complexes exhibit reasonable thermal stabilities with the tolerate temperatures ca. 255°C for 1 and 263°C for 2. The complexes display intraligand ($\pi-\pi^\ast$) fluorescence in the solid state and in DMF solutions at room temperature.

    • Syntheses, structures and properties of two dinuclear mercury(II) iodide compounds containing tetradentate tripodal amine/pentadentate N-donor Schiff base: Control of molecular and crystalline architectures by varying ligand matrices

      Subhasis Roy Soumi Chattopadhyay Somnath Choubey Kishalay Bhar Partha Mitra Barindra Kumar Ghosh

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      Two dinuclear mercury(II) iodide complexes of the types [(L1)Hg(𝜇-I)HgI3] (1) and [Hg2(L2) (I)4]·H2O (2) [L1 = tris(2-aminoethyl)amine and L2 = N,N'-(bis-(pyridin-2-yl)benzylidene)diethylenetriamine] have been synthesized and characterized usingmicroanalytical, spectroscopic, thermal and other physicochemical results. Structures of both the compounds are solved by X-ray diffraction measurements. Structural analyses show that one mercury (II) centre in 1 adopts a distorted tetrahedral geometry with an HgI4 chromophore surrounded by four iodides, while the other has a distorted trigonal bipyramidal environment with an HgN4I chromophore bound by four N atoms of L1 and one bridging iodide. Pentadentate Schiff base (L2) in 2 shows unusual binucleating bis(bidentate) behaviour to bind two different mercury(II) centres—Hg1 with an HgN3I2 chromophore in a distorted square pyramidal geometry and Hg2 with an HgN2I2 chromophore in a tetrahedral environment. Weak intermolecularN-H…I hydrogen bonds in 1 and cooperative C-H$\ldots$𝜋 and $\pi\ldots \pi$ interactions in 2 promote dimensionalities. The Schiff base complex, 2, shows intraligand ($\pi-\pi^\ast$) fluorescence in DMF solution at room temperature, whereas compound 1 containing tripodal amine is fluorescent-inactive.

    • An anti-ferromagnetic terephthalate-bridged trigonal prismatic dinuclear manganese(II) complex: Synthon of rare anion$^{\ldots} \pi$ interaction promoting dimensionality

      Somnath Choubey Soumi Chattopadhayay Kishalay Bhar Subhasis Roy Sumitava Khan Joan Ribas Barindra Kumar Ghosh

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      A dinuclear compound [Mn2(L)2(𝜇-tp)](PF6)2·3.57H2O (1) [L = N,N′-(bis(pyridin-2-yl)benzylidene)-1,3-propanediamine and tp = terephthalate dianion] has been isolated and characterized on the basis of microanalytical, spectroscopic and other physicochemical properties. X-ray structural study showed interesting bis(bidentate) bridging motif of tp in the dicationic dinuclear unit [Mn2(𝜇-tp)]2+. Each manganese(II) centre adopts a rare distorted trigonal prismatic geometry with an MnN4O2 chromophore.Chelation of the tetradentate Schiff base (L) along with bis(bidentate) bridging of two O atoms of tp complete hexacoordination around each manganese(II) centre. The dinuclear units of 1 are associated through cooperative C-H$\cdots$F hydrogen bonds and $\pi^{\cdot} \pi$, C-H$^{\cdots} \pi$ and rare anion$^{\cdots} \pi$ interactions to promote the dimensionality in a graded manner. Variable temperature magnetic susceptibility measurement of 1 in the 2-300 K temperature range revealed weak antiferromagnetic interaction presumably due to long bridging arm of tp.

    • Syntheses, structures and luminescence behaviour of some zinc(II) complexes containing acetate and tetradentate Schiff bases

      Ashis Kumar Maji Subhasis Roy Somnath Choubey Rajarshi Ghosh Barindra Kumar Ghosh

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      Two mononuclear compounds of the types pentacoordinated [Zn(L1)(OAc)]PF6·H2O (1) and hexacoordinated [Zn(L2)(OAc)]PF6 (2) [L1 = N,N′-(bis(pyridin-2-yl)formylidene)-1,3-propanediamine; L2 = N,N′-(bis(pyridin-2-yl)benzylidene)-1,4-butanediamine] have been synthesized using one-pot reactions of a 1:1:1 molar ratio of Zn(OAc)2.2H2O, L1/L2, ammonium hexafluorophosphate in MeOH at room temperature. Compounds 1 and 2 are characterized on the basis of microanalytical, spectroscopic, thermal and other physicochemical results. Single crystal X-ray structural study reveals that the zinc(II) centre in 1 is coordinated by four N atoms of the Schiff base L1 and one O atom of terminal acetate with a ZnN4O chromophore, whereas in 2, the zinc(II) centre is bound by four N atoms of the tailored Schiff base L2 and two O atoms of the chelated acetate. In the crystalline state, mononuclear units in 1 are engaged in weak cooperative intermolecular O-H⋯O and C-H⋯F hydrogen bonds affording a 1D chain. The individual units of 2 are packed by 𝜋 ⋯ 𝜋 and anion⋯ 𝜋 interactions to form a 2D sheet structure. The complexes show reasonable thermal stabilities and display intraligand 𝜋 $\to$ 𝜋 fluorescence in solid state at room temperature.

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