Rapid Access to Encapsulated Molecular Rotors via Coordination-Driven Macrocycle Formation

Macrocycle formation that relies upon trans metal coordination of appropriately placed pyridine ligands within an arylene ethynylene construct provides rapid and reliable access to molecular rotators encapsulated within macrocyclic stators. Showing no significant close contacts to the central rotators, X-ray crystallography of Ag-I-coordinated macrocycles provides plausibility for unobstructed rotation or wobbling of rotators within the central cavity. Solid-state C-13 NMR of Pd-II-coordinated macrocycles supports the notion of unobstructed movement of simple arenes in the crystal lattice. Solution H-1 NMR studies indicate complete and immediate macrocycle formation upon the introduction of Pd-II to the pyridyl-based ligand at room temperature. Moreover, the formed macrocycle is stable in solution; a lack of significant changes in the H-1 NMR spectrum upon cooling to -50 & DEG;C is consistent with the absence of dynamic behavior. The synthetic route to these macrocycles is expedient and modular, providing access to rather complex constructs in four simple steps involving Sonogashira coupling and deprotection reactions.

Automated summary

Macrocycle formation through trans metal coordination enables the rapid and reliable encapsulation of molecular rotators within macrocyclic stators. Crystallographic analysis shows that the rotators within Ag-I-coordinated macrocycles can rotate or wobble unobstructed within the central cavity. The movement of simple arenes in Pd-II-coordinated macrocycles is supported by solid-state C-13 NMR. Solution H-1 NMR studies demonstrate immediate macrocycle formation upon introduction of Pd-II to the pyridyl-based ligand at room temperature. The synthetic route to these macrocycles is efficient and modular, involving Sonogashira coupling and deprotection reactions.