ISSN:
0947-6539
Keywords:
bridging ligands
;
coordination
;
copper compounds
;
exchange coupling
;
magnetic properties
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Magnetic long-range exchange coupling between two unpaired electrons of two copper(II) ions in a square-pyramidal ligand environment (dx2-y2)1, which are rigidly separated by 〉 10 Å by an organic spacer ligand (e.g., a μ-dicarboxylato ligand) has been systematically studied. The following complexes have been synthesized: [{LCu(OH2)}2(μ-terephthalato)](ClO4)2 (I), [LCuII(OH2)(benzoato)](CIO4) (2), [{LCuII(NCS)}2(μ-terephthalato)]-2 CH3OH (3), [{LCuII(NCS)}2 (μ-4,4′-oxybisbenzoato)] · 3 CH3OH (4), [{LCuII(OH2)}2 (μ-tetrafluoroterephthalato)](CIO4)2 (5), [{LCuII(OH2)}2{LCuII}2 (μ-tetrafluorobenzoato)3](CIO4)2 · 6 H2O (6), [{LCuII(OH2)}2 (μ-biphenyl-4,4′-dicarboxylato)](CIO4)2 (7), [LCuII(μ-biphenyl-4,4′-dicarboxylato)]n (HZO)2n (8), [{LCuII(NCS)}2 (μ-biphenyl-4.4′-dicarboxylato)] (9), [{LCu(OH2)}2, (μ-trans,trans-2,4-hexadien1,6-dicarboxylato)] (CIO4)2 (10) (L = 1,4,7-trimethyl-1,4,7-triazacyclononane). Complexes 1, 2, 3, 4, and 6 have been characterized by X-ray crystallography; the structure of 1 has been described previously.[15] Temperature-dependent magnetic susceptibility data for all complexes have been measured over the range 2.0-298 K. In complexes 2, 3, 4, 6, 8, and 9 only very weak, if any, intermolecular antiferromagnetic or, in the case of 6, ferromagnetic coupling has been observed (|J|≤2cm-1; H= -2JS1 S2 S1 = S2 = 1/2). In contrast, in complexes 5 (2J=-80cm-1), 7(2J=-62cm-1), and 10 (2J = -100 cm-1) relatively strong intramolecular antiferromagnetic exchange coupling has been detected. The intramolecular Cu…Cu separation is 11.3Å in 5, 15.6 Å in 7, and approximately 12.0Å in 10. These data demonstrate that intramolecular antiferromagnetic exchange coupling of considerable magnitude is possible over distances 〉 15 Å, provided that the effective magnetic orbitals are favorably aligned.
Additional Material:
16 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/chem.19950010904
Permalink
