‘meta-Wurster's crowns’: The synthesis and properties of meta-Phenylenediamine-based macrocycles

✍ Scribed by John W. Sibert; Daniel J. Seyer; Greg R. Hundt

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 297 KB
• Volume: 2
• Category: Article
• ISSN: 1472-7862
• DOI: 10.1016/s1472-7862(03)00090-x

✦ Synopsis

meta-Wurster's crowns are a new class of hosts that incorporate the meta-phenylenediamine moiety within a macrocyclic framework. We have used a Pd-catalyzed amination procedure in the synthesis of representative m-Wurster's crown members containing aza-12-crown-4, aza-15-crown-5 and aza-18-crown-6 macrocycles and bis/tris(macrocycles) containing aza-15-crown-5 units with yields ranging from 70 to 86%. Competitive alkali metal ion binding experiments, monitored by electrospray mass spectrometry, revealed that the monocyclic crowns form 1:1 complexes with the cation that best matches the crown topology. 13 C NMR studies confirm the results from mass spectrometry and show the m-phenylenediamine moiety to interact with the bound ions, thus, establishing its participation as a direct link in the stabilization of the complexes. The bis and tris(macrocycles) were shown by cyclic voltammetry and 13 C NMR spectroscopy to coordinate two and three sodium ions, respectively. Anodic shifts in the oxidation potentials of the ligands upon complexation were driven by complex stability, not charge density, with the largest shifts resulting from the cation that appears to best fit the crown.