Magnetostructural Correlations in Bis(μ2-phenoxide)-Bridged Macrocyclic Dinuclear Copper(II) Complexes. Influence of Electron-Withdrawing Substituents on Exchange Coupling
- 1 January 1996
- journal article
- research article
- Published by American Chemical Society (ACS) in Inorganic Chemistry
- Vol. 35 (11) , 3117-3125
- https://doi.org/10.1021/ic9514197
Abstract
Macrocyclic dicopper(II) complexes derived from 2,6-di(R)formylphenols and various linking diamines are surveyed and their magnetic and structural properties assessed. For those systems with “flat” dinuclear centers and no electronic perturbations associated with electron-withdrawing ligands or ligand groups, the complexes exhibit a “straight-line” relationship between exchange integral and phenoxide bridge angle. Within the angle range 98.8−104.7°, 11 complexes are included with −2J in the range 689−902 cm-1. When electron-withdrawing species are present, either as ligands or as groups bound to the macrocycle itself, considerable suppression of the antiferromagnetic exchange component is observed. Single-crystal X-ray diffraction studies are reported for three complexes. [Cu2(L1)(H2O)2]F2(CH3OH)2 (1) crystallized in the triclinic system, space group P1̄, with a = 8.1878(5) Å, b = 9.0346(7) Å, c = 10.4048(7) Å, α = 103.672(6)°, β = 101.163(5)°, γ = 104.017(5)°, and Z = 1. [Cu2(L2)Cl2] [Cu2(L2) (H2O)2]Cl(ClO4)·5.5H2O (2) crystallized in the monoclinic system, space group P21/n, with a = 14.4305(5) Å, b = 24.3149(8) Å, c = 18.6584(8) Å, β = 111.282(3)°, and Z = 4. [Cu2(L3)(H2O)2](BF4)2 (3) crystallized in the triclinic system, space group P1̄, with a = 8.6127(4) Å, b = 8.6321(7) Å, c = 10.8430(10) Å, a = 74.390(10)°, β = 86.050(10)°, γ = 76.350(10)°, and Z = 2. Square pyramidal copper ion stereochemistries are observed in all cases, with axially coordinated halogens or water molecules. Strong antiferromagnetic exchange is observed for all complexes (−2J = 784(8) cm-1, Cu−O−Cu 103.65(10)° (1); −2J = 801(11) cm-1, Cu−O−Cu 102.4(3), 107.5(3), 102.9(3), 106.1(3)° (2); −2J = 689(3) cm-1, Cu−O−Cu 98.8(4)° (3)). The presence of electron-withdrawing CN groups on the periphery of the macrocyclic ligand leads to substantially reduced antiferromagnetic exchange.Keywords
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