Two Functional Three-Dimensional Cd(II)-Coordination Polymers Based on Carboxybenzyl Viologen Ligands

Two kinds of Cd(II) coordination polymers (CPs) [Cd(cbbpy)(NDC)·3H 2 O] n ( 1 ) and [Cd 2 (bcbpy) 2 ( m -BDC) 2 ] n ( 2 ) have been successfully synthesized based on two carboxybenzyl viologen ligands (1-(3-carboxybenzyl)-4,4′-bipyridinium chloride = Hcbbpy·Cl, 1,1′-bis(3-carboxybenzyl)-4,4′-bipyridinium dichloride = H 2 bcbpy·Cl 2 ) as predesigned ligands, in combination with two aromatic carboxylic acids (1,4-naphthalenedicarboxylic acid = 1,4-H 2 NDC, 1,3-benzenedicarboxylic acid = m -H 2 BDC) as the secondary building linkers. Single crystal X-ray analysis reveals that complex 1 features a 4-fold interpenetrating three-dimensional (3D) structure with two coordination atoms (N/O), while complex 2 possesses a noninterpenetrating 3D structure with complete O coordination. Similar to viologen-based materials, the two CPs show pronounced photochromic responses following UV irradiation. Additionally, both CPs exhibit the “on/off” behavior of photoluminescence during the coloring-decoloration process. In particular, complex 2 is also suitable for erasable inkless printing.