Novel Polythreaded Coordination Polymer: from an Armed-Polyrotaxane Sheet to a 3D Polypseudorotaxane Array, Photo- and Thermochromic Behaviors

A novel coordination compound, {[Cd(BDC)(Bpybc)1.5]·10H2O}n, obtained by the reaction of CdCl2 with 1,1′-bis(4-carboxybenzyl)-4,4′-bipyridinium dichloride (H2BpybcCl2) and 1,4-benzenedicarboxylic acid (H2BDC), 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.