One new complex of Mn(III), {[Mn2(salen)2(HCOO)] (ClO4)(1.5CH3OH)(0.5H2O)}n (1) has been synthesized and characterized by single-crystal X-ray diffraction analyses. It consists of dinuclear cationic units [Mn2(salen) 2(HCOO)]+, joined together by weak Mn⋯O (phenoxido) interactions to form an alternating phenoxido- and formato-bridged 1D polymer. The complex acts as an efficient catalyst in the alkene ((E)- stilbene, styrene) epoxidation reaction in presence of the terminal oxidant PhIO in solvents CH3CN and CH2Cl2 independently and it retains its reactivity with high efficiency beyond three cycles. © 2012 Elsevier B.V. All rights reserved.

ASHUTOSH GHOSH

Chemistry

P KAR

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Inorganica Chimica Acta

A multifunctional porous metal organic framework based on mixed-valence hexa-nuclear [Mn III 2Mn II 4O 2(pyz) 2(C 6H 5CH 2COO) 10] (pyz = pyrazine) units has been synthesized. The complex has been characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction analysis, and variable-temperature magnetic measurements. The structural analysis reveals that the bidentate pyz molecules connect each [Mn 6] unit to its four [Mn 6] neighbors through the peripheral Mn(II) centers, giving rise to a three-dimensional (3D) distorted diamond-like porous framework. Variable-temperature (2-300 K) magnetic susceptibility measurements show the presence of dominant antiferromagnetic interactions within the discrete [Mn 6] cluster that have been fitted with a model containing three exchange constants developed for the complex (J 1 = -8.6 cm -1, J 2 = -3.9 cm -1, and J 3 = -100.0 cm -1). Using 3,5-di-tert-butyl catechol (3,5-DTBC) as the substrate, catecholase activity of the complex has been studied; the turn over number is determined to be of 2547 h -1 in acetonitrile. This porous compound shows remarkable selectivity for adsorption of CO 2 over N 2 that may be correlated with the effect of window flexibility of the pore to the corresponding adsorbate molecules. © 2012 American Chemical Society.

Inorganic Chemistry

Antiferromagnetic porous metal-organic framework containing mixed-valence [Mn II 4Mn III 2(Î¼ 4-O) 2] 10+ units with catecholase activity and selective gas adsorption

Two new Mn(III) complexes of formulas [MnL 1(N 3)(OMe)] 2 (1) and [MnL 2(N 3) 2] n (2) have been synthesized by using two tridentate NNO-donor Schiff base ligands HL 1{(2-[(3-methylaminoethylimino)- methyl]-phenol)} and HL 2 {(2-[1-(2-dimethylaminoethylimino)methyl] phenol)}, respectively. Substitution of the H atom on the secondary amine group of the N-methyldiamine fragment of the Schiff base by a methyl group leads to a drastic structural change from a methoxido-bridged dimer (1) to a single μ 1,3-azido-bridged 1D helical polymer (2). Both complexes were characterized by single-crystal X-ray structural analyses and variable-temperature magnetic susceptibility measurements. The magnetic properties of compound 1 show the presence of weak ferromagnetic exchange interactions mediated by double methoxido bridges (J = 0.95 cm -1). Compound 2 shows the existence of a weak antiferromangetic coupling along the chain (J = -8.5 cm -1) through the single μ 1,3-N 3 bridge with a spin canting that leads to a long-range antiferromagnetic order at T c ≈ 9.3 K and a canting leading to a weak ferromagnetic long-range order at T c ≈ 8.5 K. It also exibits metamagnetic behavior at low temperatures with a critical field of ca.1.2 T due to the weak antiferromagnetic interchain interactions that appear in the canted ordered phase. © 2012 American Chemical Society.

A ferromagnetic methoxido-bridged Mn(III) dimer and a spin-canted metamagnetic Î¼ 1,3 -azido-bridged chain

Three new MnIIIcomplexes2(OCn)](ClO 4)}n (1), {[Mn2(salen)2(OPh)] (ClO4)}n (2) and {[Mn2(salen) 2(OBz)](ClO4)}2 (3) (where salen = N,N′-bis(salicylidene)-1,2-diaminoethane dianion, OCn = cinnamate, OPh = phenylacetate and OBz = benzoate), have been synthesized and characterized structurally and magnetically. The crystal structures reveal that all three structures contain syn-anti carboxylate-bridged dimeric [Mn2(salen) 2(OOCR)]+ cations (OOCR = bridging carboxylate) that are joined together by weak Mn⋯O(phenoxo) interactions to form infinite alternating chain structures in 1 and 2, but the relatively long Mn⋯O(phenoxo) distance [3.621(2) Å] in 3 restricts this structure to tetranuclear units. Magnetic studies showed that 1 and 2 exhibited magnetic long-range order at TN = 4.0 and 4.6 K (TN = Néel transition temperature), respectively, to give spin-canted antiferromagnetic structures. Antiferromagnetic coupling was also observed in 3 but no peaks were recorded in the field-cooled magnetization (FCM) or zero-field-cooled magnetization (ZFCM) data, indicating that 3 remained paramagnetic down to 2 K. This dominant antiferromagnetic coupling is attributed to the carboxylate bridges. The ferromagnetic coupling expected due to the Mn-O(phenoxo)⋯Mn bridge plays an auxiliary role in the magnetic chain, but is an essential component of the bulk magnetic properties of the material. © 2011 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

European Journal of Inorganic Chemistry

Spin-canted antiferromagnetic phase transitions in alternating phenoxo- and carboxylato-bridged MnIII-salen complexes

An attempt for the synthesis of a MnIII complex with unsymmetrical tetradentate Schiff base ligand uspen (1:1:1 condensate of salicylaldehyde, 2,4-pentanedione and 1,2-ethanediamine) resulted in the isolation of a novel complex, {[{Mn(salen)}{Mn(uspen)}(HCOO)]·ClO 4}n (1) as an intermediate species that contains both the unsymmetrical and symmetrical tetradentate ligand uspen and salen (2:1 condensate of salicylaldehyde and 1,2-ethanediamine) respectively. The structure of the complex shows that half of the unsymmetrical Schiff base, uspen rearranged to its symmetrical analogue, salen. A phenoxo bridged dinuclear MnIII complex [Mn(salen)(sal)]2·2H2O (2) with only the symmetrical Schiff base was also obtained. Compound 1 that contains both unsymmetrical and symmetrical Schiff base ligands in one molecule is unprecedented and provides an insight into the unsymmetrical to symmetrical rearrangement of tetradentate Schiff base ligand. Complex 2 acts as an efficient catalyst in the alkene ((E)-stilbene, styrene) epoxidation reaction in presence of two terminal oxidants PhIO and NaOCl in solvents CH3CN and CH2Cl2 independently and it retains its reactivity with high efficiency for a long time. © 2010 Elsevier B.V. All rights reserved.

Isolation of a novel intermediate during unsymmetrical to symmetrical rearrangement of a tetradentate Schiff base ligand in a manganese(III) complex: Catalytic activity of the rearranged product towards alkene epoxidation

Structural and magnetic characterization of compound {[Ni 2(L)2(OAc)2][Ni3(L) 2(OAc)4]}-2CH3CN (3) (HL = the tridentate Schiff base ligand, 2-[(3-methylamino-propylimino)-methyl]-phenol) shows that it is a rare example of a crystal incorporating a dinuclear Ni(ll) compound, [Ni2(L)2(OAc)2], and a trinuclear one, [Ni 3(L)2(OAc)4]. Even more unusual is the fact that both Ni (II) complexes, [Ni2(L)2(OAc)2] (1) and [Ni3(L)2(OAc)4(H2O) 2] · CH2Cl2· 2CH3OH (2), have also been isolated and structurally and magnetically characterized. The structural analysis reveals that the dimeric complexes [Ni 2(L)2(OAc)2] in cocrystal 3 and in compound 1 are almost identical-in both complexes, the Ni(ll) ions possess a distorted octahedral geometry formed by the chelating tridentate ligand (L), a chelating acetate ion, and a bridging phenoxo group with very similar bond angles and distances. On the other hand, compound 2 and the trinuclear complex in the cocrystal 3 show a similar linear centrosymmetric structure with the tridentate ligand coordinated to the terminal Ni(ll) and linked to the central Ni(ll) by phenoxo and carboxylate bridges. The only difference is that a water molecule found in 2 is not present in the trinuclear unit of complex 3; instead, the coordination sphere is completed by an additional bridging oxygen atom from an acetate ligand. Variable-temperature (2-300 K) magnetic susceptibility measurements show that the dinuclear unit is antiferromagnetically coupled in both compounds (2J= -36.18 and -29.5 cm-1 in 1 and 3, respectively), whereas the trinuclear unit shows a very weak ferromagnetic coupling in compound 3 (2J= 0.23 cm-1) and a weak antiferromagnetic coupling in 2 (2J= -8.7(2) cm-1) due to the minor changes in the coordination sphere. © 2009 American Chemical Society.

Journal	Data powered by TypesetInorganica Chimica Acta
Publisher	Data powered by TypesetElsevier S.A.
ISSN	0020-1693
Open Access	No