High Thermal Durability of Water-Free Copper-Octacyanotungsten-Based Magnets Containing Halogen Bonds
- Publication date
- Publisher
Abstract
Two-dimensional (2-D) cyano-bridged Cu–W bimetallic assemblies that include halogen-substituted pyridine molecules, [Cu<sup>II</sup>(3-iodopyridine)<sub>4</sub>][Cu<sup>II</sup>(3-iodopyridine)<sub>2</sub>]<sub>2</sub>[W<sup>V</sup>(CN)<sub>8</sub>]<sub>2</sub> (<b>1</b>) (triclinic crystal structure, <i>P</i>1̅ space group), [Cu<sup>II</sup>(3-bromopyridine)<sub>4</sub>][Cu<sup>II</sup>(3-bromopyridine)<sub>2</sub>]<sub>2</sub>[W<sup>V</sup>(CN)<sub>8</sub>]<sub>2</sub> (<b>2</b>) (triclinic, <i>P</i>1̅), and [Cu<sup>II</sup>(3-chloropyridine)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>][Cu<sup>II</sup>(3-chloropyridine)<sub>2</sub>]<sub>2</sub>[W<sup>V</sup>(CN)<sub>8</sub>]<sub>2</sub>·4H<sub>2</sub>O (<b>3</b>) (monoclinic, <i>P</i>2<sub>1</sub>/<i>c</i>), were synthesized. Thermogravimetric measurements demonstrate that <b>1</b> and <b>2</b> have high thermal durability up to ca. 150 °C (423 K) due to the lack of water molecules in the crystal and the stacked Cu–W 2-D layers with halogen bonding between halogen-substituted pyridine and the cyano nitrogen of octacyanotungstate. In contrast, <b>3</b> exhibits weight loss above ca. 50 °C (323 K) as the water molecules between the 2-D layers are removed upon heating. Magnetic measurements show that <b>1</b>–<b>3</b> are ferromagnets due to parallel ordering of the magnetic spins on Cu<sup>II</sup> (<i>S</i> = 1/2) and W<sup>V</sup> (<i>S</i> = 1/2) with Curie temperatures (<i>T</i><sub>C</sub>) of 4.7 K (<b>1</b>), 5.2 K (<b>2</b>), and 7.2 K (<b>3</b>)
