Two pentanuclear NiII complexes, [Ni5(L 1)2(CH3COO)6(OH)2(MeOH) 2] (1) and [Ni5(L2)2(CH 3COO)6(OH)2(H2O)2] (2), and one tetranuclear CuII complex, [Cu4(L 3)2(CH3COO)4(O)] (3), have been synthesized from phenol-based "end-off" compartmental ligands HL 1 to HL3 {HL1 = 2,6-bis[ethyl(2-thienyl) iminomethyl]-4-tert-butylphenol; HL2 = 2,6-bis[ethyl(2-thienyl) iminomethyl]-4-chlorophenol and HL3 = 2,6-bis[ethyl(2-thienyl) iminomethyl]-4-methylphenol, respectively}. The complexes have been structurally characterized and their magnetic properties have been investigated within the temperature range 2.2-300 K. Complexes 1 and 2 comprise two dinuclear [Ni 2L2] units linked to a central Ni ion by bridging μ3-hydroxo groups. The cluster is stabilized by syn-syn-μ1,3-bridging and μ1,1,3-bridging acetate anions. The structural analysis of 3 revealed two crystallographically independent complexes that consisted of a tetrahedron of CuII ions connected to a central μ4-oxo species and further bridged by four acetate groups along four of the six edges of the Cu4 core. The other two edges are occupied by μ-phenoxo bridges from the deprotonated L 3 ligand. Magnetic investigations revealed both ferromagnetic and antiferromagnetic interactions in 1 and 2 with single-ion zero-field splitting of magnitude comparable to exchange interactions, and strong antiferromagnetic interactions in 3. Variable-temperature magnetic studies of two structurally characterized pentanuclear nickel(II) complexes and one tetranuclear copper(II) complex synthesized from a series of compartmental ligands reveal both ferromagnetic and antiferromagnetic interactions in the pentanickel complexes and strong antiferromagnetic interactions in tetracopper cluster. Copyright © 2014 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

S DAS

A GUHA

R SANYAL

E ZANGRANDO

D DAS

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

European Journal of Inorganic Chemistry

Two diastereomeric forms of the &mu;4-oxo-bridged tetranuclear copper(II) complex [Cu4(O)(L)2(Ac)4] (where L=N2,O-donor Schiff-base ligand and Ac = acetate anion), differing for the bridging arrangement of the carboxylate groups, were individually synthesized and structurally characterized. Their formation was ratio- nalized by DFT calculation and their catecholase-like activity was studied.

Inorganic Chemistry Communications

Diastereomerism in tetranuclear copper(II) complexes of a phenol based “end-off” compartmental ligand

The reaction of a tridentate Schiff base ligand HL (2-[(3- dimethylaminopropylimino)-methyl]-phenol) with Ni(II) acetate or perchlorate salts in the presence of azide as coligand has led to two new Ni(II) complexes of formulas [Ni 3L 2(OAc) 2(μ 1,1- N 3) 2(H 2O) 2]·2H 2O (1) and [Ni 2L 2(μ 1,1-N 3) (μ 1,3-N 3)] n(2). Single crystal X-ray structures show that complex 1 is a linear trinuclear Ni(II) compound containing a μ 2-phenoxido, an end-on (EO) azido and a syn-syn acetato bridge between the terminal and the central Ni(II) ions. Complex 2 can be viewed as a one-dimensional (1D) chain in which the triply bridged (di-μ 2- phenoxido and EO azido) dimeric Ni 2 units are linked to each other in a zigzag pattern by a single end-to-end (EE) azido bridge. Variable-temperature magnetic susceptibility studies indicate the presence of moderate ferromagnetic exchange coupling in complex 1 with J value of 16.51(6) cm -1. The magnetic behavior of 2 can be fitted in an alternating ferro- and antiferromagnetic model [J FM = +34.2(2.8) cm -1 and J AF = -21.6(1.1) cm -1] corresponding to the triple bridged dinuclear core and EE azido bridge respectively. Density functional theory (DFT) calculations were performed to corroborate the magnetic results of 1 and 2. The contributions of the different bridges toward magnetic interactions in both compounds have also been calculated. © 2012 American Chemical Society.

Fulltext

Inorganic Chemistry

A rare phenoxido/acetato/azido bridged trinuclear and an unprecedented phenoxido/azido bridged one-dimensional polynuclear nickel(II) complexes: Synthesis, crystal structure, and magnetic properties with theoretical investigations on the exchange mechanis

Five new nickel(11) complexes [Ni2L2(N 3)2(H2O)2] (1), [Ni 2L2(NO3)2] (2), [Ni 2L2(O2CPh)(CH3OH) 2]CIO4.0.5CH3OH (3), [Ni3L 2(O2CPh)4] (4), and [Ni2L 2(NO2)2]n (5) have been synthesized by using a tridentate Schiff base ligand, HL (2-[(3-Methylamino-propylimino)- methyl]-phenol), and the polyatomic monoanions N3-, NO3-, PhCOO", or NO2-. The complexes have been structurally and magnetically characterized. The structural analysis reveals that in all five complexes, the Ni(11) ions possess a distorted octahedral geometry. Complexes 1 and 2 are dinuclear with di-μ-1, 1-azido and di-μ2-phenoxo bridges, respectively. Complex 3 is also a di-μ2-phenoxo-bridged dinuclear Ni(11) complex but has an additional syn-syn benzoate bridge. Compound 4 possesses a linear trinuclear structure with the tridentate Schiff base ligand coordinated to the terminal nickel atoms which are linked to the central Ni(11) by phenoxo and carboxylate bridges. Complex 5 consists of a dinuclear entity, bridged by di-μ2-phenoxo together with a c/s-(μ-nitrito-1κO: 2κN) nitrite ion. The dinuclear units are linked each other by another bridging trans-(μ-nitrito-1κO:2κN) nitrite to form a Ni(11) chain that shows the presence of unprecedented alternating cis- and trans-N, O bridging mode of the nitrite anion. Variable-temperature magnetic susceptibility measurements of complex 1 indicate the presence of ferromagnetic exchange interactions within the dimer (J = 23.5(3) cm-1) together with antiferromagnetic interdimer interactions (J = -0.513(3) cm-1), whereas compounds 2 and 3 show intradimer antiferromagnetic interactions (J= -24.27(6) and -16.48(4) cm-1, respectively). Ferromagnetic coupling (J = 6.14(2) cm-1) is observed in complex 4 for the linear centro-symmetric Ni(11) trimer, whereas complex 5 shows an alternating intra-chain antiferromagnetic coupling (J1 = -32.1(1) cm-1 and J2 = -3.2(1) cm-1). © 2009 American Chemical Society.

The crucial role of polyatomic anions in molecular architecture: Structural and magnetic versatility of five nickel(11) complexes derived from a N.N.O-donor schiff base ligand

A series of dinuclear copper(II) complexes has been synthesized with the aim to investigate their applicability as potential structure and function models for the active site of catechol oxidase enzyme. They have been characterized by routine physicochemical techniques as well as by X-ray single-crystal structure analysis: [Cu2(H2L22 )(OH)(H2O)(NO3)](NO3)3 &middot; 2H2O (1), [Cu(HL14 )(H2O)(NO3)]2(NO3)2 &middot; 2H2O (2), [Cu(L11 )(H2O)(NO3)]2 (3), [Cu2(L23 )(OH)(H2O)2](NO3)2, (4) and [Cu2(L21 )(N3)3] (5) [L1 ) 2-formyl-4-methyl-6R-iminomethyl-phenolato and L2 ) 2,6-bis(R-iminomethyl)-4-methyl-phenolato; for L11 and L21 , R ) N-propylmorpholine; for L22 , R ) N-ethylpiperazine; for L23 , R ) N-ethylpyrrolidine, and for L14 , R ) N-ethylmorpholine]. Dinuclear 1 and 4 possess two &ldquo;end-off&rdquo; compartmental ligands with exogenous &mu;-hydroxido and endogenous &mu;-phenoxido groups leading to intermetallic distances of 2.9794(15) and 2.9435(9) &Aring;, respectively; 2 and 3 are formed by two tridentate compartmental ligands where the copper centers are connected by endogenous phenoxido bridges with Cu-Cu separations of 3.0213(13) and 3.0152(15) &Aring;, respectively; 5 is built by an end-off compartmental ligand having exogenous &mu;-azido and endogenous &mu;-phenoxido groups with a Cu-Cu distance of 3.133(2) &Aring; (mean of two independent molecules). The catecholase activity of all of the complexes has been investigated in acetonitrile and methanol medium by UV-vis spectrophotometric study using 3,5-di-tert-butylcatechol (3,5-DTBC) and tetrachlorocatechol (TCC) as substrates. In acetonitrile medium, the conversion of 3,5-DTBC to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) catalyzed by 1-5 is observed to proceed via the formation of two enzyme-substrate adducts, ES1 and ES2, detected spectroscopically for the first time. In methanol medium no such enzyme-substrate adduct has been detected, and the 3,5-DTBC to 3,5-DTBQ conversion is observed to be catalyzed by 1-5 very efficiently. The substrate TCC forms an adduct with 2-5 without performing further oxidation to TCQ due to the high reduction potential of TCC (in comparison with 3,5-DTBC). But most interestingly, 1 is observed to be effective even in TCC oxidation, a process never reported earlier. Kinetic experiments have been performed to determine initial rate of reactions (3,5-DTBC as substrate, in methanol medium) and the activity sequence is 1 &gt; 5 &gt; 2 ) 4 &gt; 3. A treatment on the basis of Michaelis-Menten model has been applied for kinetic study, suggesting that all five complexes exhibit very high turnover number, especially 1, which exhibits turnover number or Kcat of 3.24 &times; 104 (h-1 ), which is &sim;3.5 times higher than the most efficient catalyst reported to date for catecholase activity in methanol medium.

Catechol Oxidase Activity of a Series of New Dinuclear Copper(II) Complexes with 3,5-DTBC and TCC as Substrates: Syntheses, X-ray Crystal Structures, Spectroscopic Characterization of the Adducts and Kinetic Studies

Three new polynuclear copper(II) complexes of 2-picolinic acid (Hpic), {[Cu 2(pic) 3(H 2O)]ClO 4}., (1), {[Cu 2(pic) 3-(H 2O)]BF 4} n (2), and [Cu 2(pic) 3(H 2O) 2(NO 3)] n (3), have been synthesized by reaction of the "metalloligand" [Cu-(pic) 2] with the corresponding copper(II) salts. The compounds are characterized by single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. Compounds 1 and 2 are isomorphous and crystallize in the triclinic system with space group P1, while 3 crystallizes in the monoclinic system with space group P2 1ln. The structural analyses reveal that complexes 1 and 2 are constructed by "fish backbone" chains through syn-anti (equatorial-equatorial) carboxylate bridges, which are linked to one another by syn-anti (equatorial-axial) carboxylate bridges, giving rise to a rectangular grid-like two-dimensional net. Complex 3 is formed by alternating chains of syn-anti carboxylate-bridged copper(II) atoms, which are linked together by strong H bonds involving coordinated nitrate ions and water molecules and uncoordinated oxygen atoms from carboxylate groups. The different coordination ability of the anions along with their involvement in the H-bonding network seems to be responsible for the difference in the final polymeric structures. Variable-temperature (2-300 K) magnetic susceptibility measurement shows the presence of weak ferromagnetic coupling for all three complexes that have been fitted with a fish backbone model developed for 1 and 2 (J = 1.74 and 0.99 cm -1; J′ = 0.19 and 0.25 cm -1, respectively) and an alternating chain model for 3 (J = 1.19 cm -1 and J′ = 1.19 cm -1). © 2007 American Chemical Society.

Anion-directed synthesis of metal-organic frameworks based on 2-picolinate Cu(II) complexes: A ferromagnetic alternating chain and two unprecedented ferromagnetic fish backbone chains

Syntheses, characterization, and magneto-structural analyses in Î¼1,3-acetato-bridged tetracopper(II) and Î¼1,3- and Î¼1,1,3-acetato-bridged pentanickel(II) clusters

Journal	Data powered by TypesetEuropean Journal of Inorganic Chemistry
Publisher	Data powered by TypesetWiley-VCH Verlag
ISSN	1434-1948