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Bāruipur, India

Naiya S.,University of Calcutta | Naiya S.,Susil Kar College | Drew M.G.B.,University of Reading | Diaz C.,University of Barcelona | And 2 more authors.
European Journal of Inorganic Chemistry | Year: 2011

Two new Fe III complexes, [Fe 2L 2(μ-OMe) 2(NCS) 2] (1) and [Fe 2L 2(μ-N 3) 2(N 3) 2] (2), have been synthesized using a N,N,O-donor tridentate Schiff base ligand HL {2-[(2- dimethylaminoethylimino)methyl]phenol}, the condensation product of salicylaldehyde and N,N-dimethyl-1,2-diaminoethane. The complexes were characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. Both crystal structures are centrosymmetric dimers containing two Fe III atoms, which are bridged in compound 1 by two methoxy anions and in compound 2 by two μ-1,1-azides. The chelating tridentate Schiff base and a terminal thiocyanato (for 1) or azido (for 2) group complete the hexacoordination of the distorted octahedral environment of each iron center. The magnetic properties of compound 1 show the presence of antiferromagnetic exchange interactions mediated by double methoxy bridges (J =-29.45 cm -1). Compound 2 shows the presence of very weak ferromagnetic exchange interactions mediated by double μ-1,1-N 3 bridges (J = 1.08 cm -1). A very rare μ-1,1-azido-bridged and a μ-OMe-bridged dinuclear Fe III compound with a tridentate N,N,O-donor Schiff base have been synthesized and characterized structurally. The former is only the third example of μ-1,1-azido bridges in Fe III. The variable-temperature magnetic studies show that the former is ferromagnetically and the latter antiferromagneticallycoupled. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Naiya S.,University of Calcutta | Naiya S.,Susil Kar College | Wang H.-S.,Nanjing University | Drew M.G.B.,University of Reading | And 2 more authors.
Dalton Transactions | Year: 2011

Four new nickel(ii) complexes, [Ni2L2(NO 2)2]·CH2Cl2·C 2H5OH, 2H2O (1), [Ni2L 2(DMF)2(μ-NO2)]ClO4·DMF (2a), [Ni2L2(DMF)2(μ-NO2)] ClO4 (2b) and [Ni3L'2(μ3-NO 2)2(CH2Cl2)]n·1. 5H2O (3) where HL = 2-[(3-amino-propylimino)-methyl]-phenol, H 2L' = 2-({3-[(2-hydroxy-benzylidene)-amino]-propylimino}- methyl)-phenol and DMF = N,N-dimethylformamide, have been synthesized starting with the precursor complex [NiL2]·2H2O, nickel(ii) perchlorate and sodium nitrite and characterized structurally and magnetically. The structural analyses reveal that in all the complexes, NiII ions possess a distorted octahedral geometry. Complex 1 is a dinuclear di-μ2-phenoxo bridged species in which nitrite ion acts as chelating co-ligand. Complexes 2a and 2b also consist of dinuclear entities, but in these two compounds a cis-(μ-nitrito-1κO:2κN) bridge is present in addition to the di-μ2-phenoxo bridge. The molecular structures of 2a and 2b are equivalent; they differ only in that 2a contains an additional solvated DMF molecule. Complex 3 is formed by ligand rearrangement and is a one-dimensional polymer in which double phenoxo as well as μ-nitrito-1κO:2κN bridged trinuclear units are linked through a very rare μ3-nitrito-1κO:2κN:3κO′ bridge. Analysis of variable-temperature magnetic susceptibility data indicates that there is a global weak antiferromagnetic interaction between the nickel(ii) ions in four complexes, with exchange parameters J of -5.26, -11.45, -10.66 and -5.99 cm-1 for 1, 2a, 2b and 3, respectively. © The Royal Society of Chemistry 2011. Source

Biswas S.,University of Calcutta | Naiya S.,University of Calcutta | Naiya S.,Susil Kar College | Drew M.G.B.,University of Reading | And 3 more authors.
Inorganica Chimica Acta | Year: 2011

The synthesis of two new sodium perchlorate adducts (1:2 and 1:3) with copper(II) "ligand-complexes" is reported. One adduct is trinuclear [(CuL 1) 2NaClO 4] (1) and the other is tetranuclear [(CuL 2) 3Na]ClO 4·EtOH (2). The ligands are the tetradentate di-Schiff base of 1,3-propanediamines and salicylaldehyde (H 2L 1) or 2-hydroxyacetophenone (H 2L 2). Both complexes have been characterized by X-ray single crystal structure analyses. In both structures, the sodium cation has a six-coordinate distorted octahedral environment being bonded to four oxygen atoms from two Schiff-base complexes in addition to a chelated perchlorate anion in 1 and to six oxygen atoms from three Schiff-base complexes in 2. We have carried out a DFT theoretical study (RI-B97-D/def2-SVP level of theory) to compute and compare the formation energies of 1:2 and 1:3 adducts. The DFT study reveals that the latter is more stabilized than the former. The X-ray crystal structure of 1 shows that the packing of the trinuclear unit is controlled by unconventional C-H···O H-bonds and Cu 2+-π non-covalent interactions. These interactions explain the formation of 1 which is a priori disfavored with respect to 2. © 2010 Elsevier B.V. All rights reserved. Source

Naiya S.,University of Calcutta | Naiya S.,Susil Kar College | Biswas S.,University of Calcutta | Drew M.G.B.,University of Reading | And 2 more authors.
Inorganica Chimica Acta | Year: 2011

Three Cu(II)-azido complexes of formula [Cu2L2(N 3)2] (1), [Cu2L2(N3) 2]·H2O (2) and [CuL(N3)]n (3) have been synthesized using the same tridentate Schiff base ligand HL (2-[(3-methylaminopropylimino)-methyl]-phenol), the condensation product of N-methyl-1,3-propanediamine and salicyldehyde). Compounds 1 and 2 are basal-apical μ-1,1 double azido bridged dimers. The dimeric structure of 1 is centrosymmetric but that of 2 is non-centrommetric. Compound 3 is a μ-1,1 single azido bridged 1D chain. The three complexes interconvert in solution and can be obtained in pure form by carefully controlling the synthetic conditions. Compound 2 undergoes an irreversible transformation to 1 upon dehydration in the solid state. The magnetic properties of compounds 1 and 2 show the presence of weak antiferromagnetic exchange interactions mediated by the double 1,1-N 3 azido bridges (J = -2.59(4) and -0.10(1) cm-1, respectively). The single 1,1-N3 bridge in compound 3 mediates a negligible exchange interaction. © 2011 Elsevier B.V. All rights reserved. Source

Biswas S.,University of Calcutta | Naiya S.,University of Calcutta | Naiya S.,Susil Kar College | Gomez-Garcia C.J.,University of Valencia | Ghosh A.,University of Calcutta
Dalton Transactions | Year: 2012

A tetra-nuclear, star-shaped hetero-metallic copper(ii)-manganese(ii) complex, [{CuL(H 2O)} 2(CuL)Mn](ClO 4) 2 (1) has been synthesized by reacting the "complex as ligand" [CuL] with Mn(ClO 4) 2 where H 2L is the tetradentate di-Schiff base derived from 1,3-propanediamine and 2-hydroxyacetophenone. Upon treatment with the polyatomic anions azide, cyanate, or thiocyanate in methanol medium, complex 1 transforms into the corresponding trinuclear species [(CuL) 2Mn(N 3) 2] (2), [(CuL) 2Mn(NCO) 2] (3) and [(CuL) 2Mn(NCS) 2] (4). All four complexes have been structurally and magnetically characterized. In complex 1 the central Mn(ii) ion is encapsulated by three terminal [CuL] units through the formation of double phenoxido bridges between Mn(ii) and each Cu(ii). In complexes 2-4 one of the CuL units is replaced by a couple of terminal azide, N-bonded cyanate or N-bonded thiocyanate ions respectively and the central Mn(ii) ion is connected to two terminal Cu(ii) ions through a double asymmetric phenoxido bridge. Variable temperature magnetic susceptibility measurements show the presence of moderate ferrimagnetic exchange interactions in all the cases mediated through the double phenoxido bridges with J values (H = -JS iS i + 1) of -41.2, -39.8 and -12.6 cm -1 (or -40.5 and -12.7 cm -1 if we use a model with two different exchange coupling constants) for the tetranuclear MnCu 3 cluster in compound 1 and -20.0, -17.3 and -32.5 cm -1 for the symmetric trinuclear MnCu 2 compounds 2-4. These ferrimagnetic interactions lead to spin ground states of 1 (5/2 - 3*1/2) for compound 1 and 3/2 (5/2 - 2*1/2) for compounds 2-4. © 2012 The Royal Society of Chemistry. Source

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