Novel polythreaded coordination polymer: From an armed-polyrotaxane sheet to a 3D polypseudorotaxane array, photo-thermochromic behaviors

A novel coordination compound, {[Cd(BDC)(Bpybc)_1.5] 10H ₂O}_n, obtained by the reaction of CdCI₂ with 1,1'-bis(4-carboxybenzyl)-4,4'-bipyridinium dichloride (H ₂BpybcCI₂) and 1,4-benzenedicar-boxylic acid (H ₂BDC), contains 1D polymeric chains that are comprised of alternating rings and rods and dangling lateral arms. These 1D polymeric motifs are interlaced via rotaxane-like mechanical linkages to give 2D armed-polyrotaxane sheets, which are further mutually polythreaded via pseudorotaxane-like mechanical linkages to form a 3D polypseudorotaxane array. Notably, a sandwich-type donor - acceptor - donor stacking is formed within each ring as a consequence of both types of polythreading in this species, and photoinduced and thermal-induced reduction of bipyridinium occurs with a color change from light yellow to blue.