Halide and Hydroxide Linearly
Bridged Bimetallic Copper(II)
Complexes: Trends in Strong Antiferromagnetic Superexchange Interactions
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Abstract
Centrosymmetric [Cu<sub>2</sub>(μ-X)(μ-<b>L</b><sub><i><b>m</b></i></sub>*)<sub>2</sub>](ClO<sub>4</sub>)<sub>3</sub> (X = F<sup>–</sup>, Cl<sup>–</sup>, Br<sup>–</sup>, OH<sup>–</sup>, <b>L</b><sub><i><b>m</b></i></sub>* = <i>m</i>-bis[bis(3,5-dimethyl-1-pyrazolyl)methyl]benzene)],
the first example of a series of bimetallic copper(II) complexes linked
by a linearly bridging mononuclear anion, have been prepared and structurally
characterized. Very strong antiferromagnetic exchange coupling between
the copper(II) ions increases along the series F<sup>–</sup> < Cl<sup>–</sup> < OH<sup>–</sup> < Br<sup>–</sup>, where −<i>J</i> = 340, 720, 808,
and 945 cm<sup>–1</sup>. DFT calculations explain this trend
by an increase in the energy along this series of the antibonding
antisymmetric combination of the p orbital of the bridging anion interacting
with the copper(II) d<sub><i>z</i><sup>2</sup></sub> orbital