Macrocyclic Dinuclear Palladium Complex as a Novel Doubly Threaded [3]Rotaxane Scaffold and Its Application as a Rotaxane Cross‐Linker
Kōji Yamamoto, Riku Nameki, Hiromitsu Sogawa, Toshikazu Takata
Abstract
Abstract A dinuclear Pd II complex possessing a cyclic ligand was developed as a novel doubly threaded [3]rotaxane scaffold and applied as a rotaxane cross‐linker reagent. The dinuclear complex (PdMC) 2 was prepared by one‐step macrocyclization followed by the double palladation reaction. 1 H NMR analysis and UV/Vis measurements revealed the formation of a doubly threaded pseudo[3]rotaxane by the complexation of (PdMC) 2 with 2 equivalents of 2,6‐disubstituted pyridine 3 through double metal coordination. The treatment of (PdMC) 2 with 2 equivalents of 4‐vinylpyridine (VP) afforded a doubly threaded [3]rotaxane cross‐linker (PdMC‐VP) 2 . Radical co‐polymerization of VP and t ‐butylstyrene in the presence of (PdMC‐VP) 2 afforded a stable rotaxane cross‐linked polymer (RCP). An elastic RCP was also prepared by using n ‐butyl acrylate as a monomer. The obtained RCPs exhibited higher swelling ability and higher mechanical toughness compared with the corresponding covalent cross‐linked polymers.