Kinetically‐Locked Metallomacrocycle for Host‐Guest Chemistry with Bulky Anions

The molecular structure of a kinetically-locked metallomacrocycle composed of three Co³⁺ ions and three diphenylanthracene derivatives with two β-diketonates on both sides was determined by X-ray crystallographic analysis and NMR analysis. The inner volume of the nanocavity of the macrocycle was estimated to be greater than 300 ų. A large anion, tetraphenylborate, is hosted by the nanocavity.

Abstract

As a robust and large molecular receptor, a kinetically-locked trinuclear Co(III) macrocycle was synthesized with bis(β-diketone) ligands having large π-panels of 9,10-diphenylanthracene moieties via a combination of Co(II)-assisted self-assembly and subsequent oxidation of the metal centers. The X-ray structure revealed that the macrocycle had a discrete nanocavity of more than 300 ų, which was surrounded by three anthracenyl panels in the middle. As the macrocycle has three cationic centres on each metal ion and a large cavity, it acts as a guest receptor for sodium tetraphenylborate. The binding constant was estimated to be 4.0×10⁻² M⁻¹ from ¹H NMR titration experiments, whereas no interaction was observed between the macrocycle and potassium 1-adamantanecarboxylate.

Zum Volltext