Tetranuclear Lanthanide(III) Complexes in a Seesaw
Geometry: Synthesis, Structure, and Magnetism
- Publication date
- Publisher
Abstract
The reaction of 2-methoxy-6-(pyridin-2-ylhydrazonomethyl)phenol
(LH) with Ln(III) (Ln = Gd, Tb, Dy, Ho) salts in the presence of an
excess of triethylamine afforded [Gd<sub>4</sub>(L)<sub>4</sub>(μ<sub>4</sub>-OH)(μ<sub>3</sub>-OH)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>]·(NO<sub>3</sub>)·4CH<sub>3</sub>CN·CH<sub>3</sub>OH·2H<sub>2</sub>O (<b>1</b>), [Tb<sub>4</sub>(L)<sub>4</sub>(μ<sub>4</sub>-OH)(μ<sub>3</sub>-OH)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>]·(NO<sub>3</sub>)·4CH<sub>3</sub>CN·3H<sub>2</sub>O (<b>2</b>), [Dy<sub>4</sub>(L)<sub>4</sub>(μ<sub>4</sub>-OH)(μ<sub>3</sub>-OH)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>]·(NO<sub>3</sub>)·6CH<sub>3</sub>CN·H<sub>2</sub>O (<b>3</b>), and [Ho<sub>4</sub>(L)<sub>4</sub>(μ<sub>4</sub>-OH)(μ-OH)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>]·(NO<sub>3</sub>)·8CH<sub>3</sub>CN·3CH<sub>3</sub>OH·2H<sub>2</sub>O (<b>4</b>). All four complexes
contain a monocationic tetranuclear core with a unique <i>seesaw</i> topology. The tetranuclear assembly is formed through the coordination
of four [L]<sup>−</sup>, one μ<sub>4</sub>-OH, two μ<sub>3</sub>-OH, and four chelating nitrate ligands, with a charge-balancing
nitrate counteranion. Magnetic studies reveal a weak antiferromagnetic
coupling throughout the series. Compound <b>1</b> can be modeled
well with an isotropic exchange between all centers parametrized by <i>J</i> = −0.09 cm<sup>–1</sup>. Compound <b>3</b> exhibits slow magnetic relaxation at low temperatures
