Exchange Coupling In Complexes Research Articles

Synthesis, crystal structure, magnetic properties and DFT study of dinuclear Ni(II) complex with the condensation product of 2-quinolinecarboxaldehyde and Girard’s T reagent

A dinuclear double end-on azido bridged Ni(II) complex [Ni2L2(μ-1,1-N3)2(N3)2] (1) with the condensation product of 2-quinolinecarboxaldehyde and trimethylammonium acetohydrazide chloride (Girard’s T reagent) (HLCl) has been synthesized and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction, magnetic measurements and DFT studies. In complex 1 intra-dimer ferromagnetic coupling between Ni2+ ions (J=+12.0(2)cm−1) and inter-dimer antiferromagnetic interaction (δ=−0.8(3)cm−1) were observed. DFT-BS calculations provided explanation of ferromagnetic exchange coupling in complex 1.

A predesigned 1D chain of alternating di-μ1,1-azido bridged dinuclear Ni(II) and pyrazine: Synthesis, structure and magnetic properties

A new Ni(II) complex, [Ni2(L)2(μ1,1-N3)2(pyz)]n (1) (where pyz=pyrazine) has been synthesized using a dinuclear di-μ1,1-azido bridged Ni2 molecular building block derived from a tridentate NNO donor Schiff base ligand, HL (2-[(3-methylamino-propylimino)-methyl]-phenol) along with pyrazine as spacer. Single crystal X-ray analysis shows that complex 1 is a 1D chain in which dimeric Ni2 units [Ni2L2(N3)2] are linked to each other by the bridging pyrazine ligand. Variable-temperature magnetic susceptibility studies indicate the presence of moderate ferromagnetic exchange coupling in complex 1 with J value of 53.54cm−1.

Triple-bridged ferromagnetic nickel(ii) complexes: A combined experimental and theoretical DFT study on stabilization and magnetic coupling

Two dinuclear [Ni2L2(o-(NO2)C6H4COO)2(H2O)] (1), [Ni2L2(p-(NO2)C6H4COO)2(H2O)]·0.5CH3OH (2) complexes and one trinuclear [Ni3L2(p-(NO2)C6H4COO)4]·C2H5OH (3) Ni(II) complex have been synthesized using a tridentate Schiff base ligand, 1-[(3-dimethylamino-propylimino)-methyl]-naphthalen-2-ol (HL) along with ortho- and para-nitro benzoate as co-ligands. All these three (1-3) complexes have been characterized by spectral analysis, X-ray crystallography and variable temperature magnetic susceptibility measurements. The structural analyses reveal that complexes 1 and 2 are dinuclear in which two μ2-phenoxido and a water molecule bridge the two Ni(ii) centers to make the complexes face sharing bioctahedra. Complex 3 is a linear triple bridged (phenoxido and carboxylato) trinuclear Ni(II) complex. Variable-temperature magnetic susceptibility studies indicate the presence of ferromagnetic exchange coupling in complexes 1-3 with J values of 25.4, 28.1 and 6.2 cm(-1) respectively. Theoretically obtained J values of 21.4 cm(-1) (for 1), 22.0 cm(-1) (for 2) and 9.3 cm(-1) (for 3) corroborate very well the experimental results. DFT calculation also shows that stronger H-bonding interactions present in the case of carboxylate based coligands stabilise the triple oxido-bridged complexes.

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 Mechanism

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(3)L(2)(OAc)(2)(μ(1,1)-N(3))(2)(H(2)O)(2)]·2H(2)O (1) and [Ni(2)L(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.

The importance of an additional water bridge in making the exchange coupling of bis(μ-phenoxo) dinickel(ii)complexes ferromagnetic

Two new nickel(II) complexes [Ni(2)L(2)(PhCOO)(2)(H(2)O)] (1), [Ni(2)L(2)(PhCH(2)COO)(2)(H(2)O)] (2) have been synthesized using a tridentate Schiff base ligand, HL (2-[(3-dimethylamino-propylimino)-methyl]-phenol) and the carboxylate monoanions, benzoate and phenylacetate, respectively. The complexes have been characterized by spectral analysis, variable temperature magnetic susceptibility measurement and crystal structure analysis. The structural analyses reveal that both complexes are dinuclear in which the distorted octahedral Ni(2+) ions share a face, bridged by one water molecule and two μ(2)-phenoxo oxygen atoms. A monodentate benzoate or phenylacetate anion and two nitrogen atoms of the chelating deprotonated Schiff base (L) complete the hexa-coordination around the metal ion. Variable-temperature magnetic susceptibility studies indicate the presence of dominant ferromagnetic exchange coupling in complexes 1 and 2 with J values of 11.1(2) and 10.9(2) cm(-1) respectively. An attempt has been made to rationalize the observed magneto-structural behavior considering the importance of the additional water bridge in the present two complexes and also in other similar species.

Ligand-induced electronic effects in the physical properties of transition metal clusters: Modulation of Mössbauer parameters and magnetic exchange couplings in complexes [formula omitted] by the R substituent

The syntheses, crystallographic, 57Fe Mössbauer and magnetic studies of the diferric complexes [Fe 2O(O 2CR) 2(phen) 2(H 2O) 2](ClO 4) 2 [R = H ( 3), CH 2F ( 4)] are reported and the results are compared to those of the previously reported analogues with R = CCl 3 ( 1) and R = CMe 3 ( 2) [Boudalis et al., Polyhedron 25 (2006) 1391]. The Mössbauer spectra of 3 and 4 consist of symmetric quadrupole-split doublets [ δ = 0.392(1) mm s −1, Δ E Q = 1.726 mm s −1 ( 3) and δ = 0.398 mm s −1, Δ E Q = 1.691 mm s −1 ( 4), at 78 K]. The magnetic couplings within 2– 4 are antiferromagnetic [ J = −140 ( 2), −129 ( 3) and −116 ( 4) cm −1, H ˆ = - 2 J S ˆ 1 · S ˆ 2 ]. The results from Mössbauer spectroscopic and variable-temperature magnetic studies are discussed in terms of structural characteristics of the complexes and the electron donating strengths of the carboxylate R substituents. In addition, the syntheses and structures of complexes [Fe 3O(O 2CR) 6(H 2O) 3](ClO 4) [R = H ( 5), CH 2F ( 6)], which were derived as by-products from the syntheses of 3 and 4, are described.

Dinuclear Complexes of MII Thiocyanate (M = Ni and Cu) Containing a Tridentate Schiff‐Base Ligand: Synthesis, Structural Diversity and Magnetic Properties

AbstractA dinuclear NiII complex, [Ni2(L)2(H2O)(NCS)2]·3H2O (1) in which the metal atoms are bridged by one water molecule and two μ2‐phenolate ions, and a thiocyanato‐bridged dimeric CuII complex, [Cu(L)NCS]2 (2) [L = tridentate Schiff‐base ligand, N‐(3‐aminopropyl)salicylaldimine, derived from 1:1 condensation of salicylaldehyde and 1,3‐diaminopropane], have been synthesized and characterized by IR and UV/Vis spectroscopy, cyclic voltammetry and single‐crystal X‐ray diffraction studies. The structure of 1 consists of dinuclear units with crystallographic C2 symmetry in which each NiII atom is in a distorted octahedral environment. The Ni–O distance and the Ni–O–Ni angle, through the bridged water molecule, are 2.240(11) Å and 82.5(5)°, respectively. The structure of 2 consists of dinuclear units bridged asymmetrically by di‐μ1,3‐NCS ions; each CuII ion is in a square‐pyramidal environment with τ = 0.25. Variable‐temperature magnetic susceptibility studies indicate the presence of dominant ferromagnetic exchange coupling in complex 1 with J = 3.1 cm–1, whereas complex 2 exhibits weak antiferromagnetic coupling between the CuII centers with J = –1.7 cm–1. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Peroxide (O 22−) as a bridging ligand for copper(II): strong exchange coupling in complexes derived from copper(I) and dioxygen

Peroxide (O 22−) as a bridging ligand for copper(II): strong exchange coupling in complexes derived from copper(I) and dioxygen