2001
DOI: 10.1021/ic000991h
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Syntheses, Crystal Structures, Magnetic Properties, and EPR Spectra of Tetranuclear Copper(II) Complexes Featuring Pairs of “Roof-Shaped” Cu2X2 Dimers with Hydroxide, Methoxide, and Azide Bridges

Abstract: Hydroxo- and methoxo-bridged tetranuclear copper(II) complexes of the tetramacrocyclic ligand 1,2,4,5-tetrakis(1,4,7-triazacyclonon-1-ylmethyl)benzene (Ldur), have been prepared from [Cu4Ldur(H2O)8](ClO4)8.9H2O (1). Addition of base to an aqueous solution of 1 gave [Cu4Ldur(mu2-OH)4](ClO4)4 (2). Diffusion of MeOH into a DMF solution of 2 produces [Cu4Ldur(mu2-OMe)4](ClO4)4.HClO4.2/3MeOH (3), a complex which hydrolyzes on exposure to moisture regenerating 2. The structurally related azido-bridged complex, [Cu4L… Show more

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Cited by 114 publications
(57 citation statements)
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References 46 publications
(107 reference statements)
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“…[25] The magnetic moment increased to 1.96 μ B at 40 K. The μ eff vs. T (K) plot shows an increase in μ eff as the temperature is lowered, followed by a steep drop at low temperatures (40 K) which is characteristic of ferromagnetic coupling [34] and is confirmed by the positive J value of +45.2 cm -1 . The data for 3 is comparable to the magnetic data observed in other ferromagnetic alkoxo-bridged [29,30] and azido-bridged [28] complexes, with similar M-O-M angles and magnetic susceptibility plots, see Table 4.…”
Section: Magnetic Measurementssupporting
confidence: 83%
See 1 more Smart Citation
“…[25] The magnetic moment increased to 1.96 μ B at 40 K. The μ eff vs. T (K) plot shows an increase in μ eff as the temperature is lowered, followed by a steep drop at low temperatures (40 K) which is characteristic of ferromagnetic coupling [34] and is confirmed by the positive J value of +45.2 cm -1 . The data for 3 is comparable to the magnetic data observed in other ferromagnetic alkoxo-bridged [29,30] and azido-bridged [28] complexes, with similar M-O-M angles and magnetic susceptibility plots, see Table 4.…”
Section: Magnetic Measurementssupporting
confidence: 83%
“…Thus, the magnetic moment and magnetic susceptibility were measured for complex 3 and the results are presented in Figure 9. Although the more usual magnetic behaviour in Cu II d 9 dimeric species is a spin-pairing anti-ferromagnetic interaction (J -ve) as we have reported in previous studies, [27] a ferromagnetic interaction (J + ve) is not unique, [28][29][30] and complex 3 represents a further example. The data were fitted to the modified Bleaney-Bowers relationship [31] given in Equation (1) for a Cu II dimer, the spin Hamiltonian H = -2J S 1 S 2 where J is the exchange coupling parameter and S 1 = S 2 = 1/2 (interacting local spins).…”
Section: Magnetic Measurementssupporting
confidence: 48%
“…Indeed, the intramolecular dihydroxobridged dinuclear copper(II) complex of L mx has been isolated by Farrugia et al, [21] and we have structurally characterised several copper(II) complexes of ligands featuring pairs of dihydroxo-bridged Cu II -tacn units attached to the meta positions of an aromatic ring. [44] Thus, at pH 7.4, significant proportions of the dinuclear Cu II complexes of L mx and L memx could be present as intramolecular hydroxobridged dimers, substantially lowering the effective concentration of hydrolytically active species in solution. The similarity in the rate constant for hydrolysis of BNPP by the complexes of L mx and L memx to that for the tacn complex appears to bear this point out.…”
Section: Crystallographymentioning
confidence: 99%
“…The preference for macrocylic ligand over unidentate and bidentate ligands has arisen from being close to the biological system [1][2][3] ,the greater stability and inertness of their complexes 4,5 and often the extreme physical properties in their complexes due to strong ligand field.…”
Section: Introductionmentioning
confidence: 99%