Metal Ion and Anion-Based “Tuning” of a Supramolecular Metallogel
2009-08-04T00:00:00Z (GMT) by
A bis(pyridylurea) ligand (<b>1</b>) forms metallogels in methanol in the presence of up to 0.5 equiv of copper(II) chloride. The metallogel has been characterized using powder X-ray diffraction, SEM, and MAS NMR spectroscopic techniques. The addition of further copper(II) chloride gives the unusual crystalline 4:3 coordination polymer [Cu<sub>3</sub>(<b>1</b>)<sub>4</sub>Cl<sub>4</sub>]Cl<sub>2</sub>·<i>n</i>H<sub>2</sub>O (<b>2</b>). In the presence of 0.5 equiv of copper(II) nitrate, the 2:1 crystalline coordination polymer [Cu(<b>1</b>)<sub>2</sub>](NO<sub>3</sub>)<sub>2</sub>·H<sub>2</sub>O·MeOH (<b>5</b>) is isolated. Both <b>2</b> and <b>5</b> have been characterized by single-crystal X-ray diffraction. Complex <b>5</b> represents a possible model for the gelator and highlights key interactions with counteranions that suggest a means to tune gel properties using anion binding. The influence of chloride and acetate anions (as their NBu<sub>4</sub><sup>+</sup> salts) on the rheological properties of the copper(II) chloride metallogels of <b>1</b> are investigated. The rheology of the anion-containing mixtures shows complex behavior with the gel structure apparently evolving over time.