Monitoring the thermodynamically-controlled formation of diimide-based resin-attached rotaxanes by gel-phase HR MAS ¹H NMR Spectroscopy

Abstract

The thermodynamically controlled self-assembly of rotaxane and pseudorotaxane systems consisting of (i) a naphthodiimide thread unit terminated at one end with a pyridine ligand, and covalently linked at the other to a gel-phase polystyrene resin support, (ii) a dinaphtho-crown ether shuttle unit, and (iii) a ruthenium carbonyl metalloporphyrin stopper unit, is investigated by high resolution magic angle spinning proton (HR MAS ¹H)NMR spectroscopy. The effects of variable concentration of the solution-phase components, the tempurature, and added Li⁺ and Na⁺ ions are described, and the limitations of the technique are addressed. The dynamic behaviour is compared directly to the solution-phase analogues, where a bulky stopper group is substituted for the polystyrene resin bead.