Syntheses, Structural Evolutions, and Properties of Cd(II) Coordination Polymers Induced by Bis(pyridyl) Ligand with Chelated or Protonated Spacer and Diverse Counteranions

Hydrothermal reaction of Cd­(II) metal salts, diverse organic acids, as well as flexible bis­(pyridyl) ligand leads to the formation of 10 complexes, namely, [Cd2LCl4]n (1), [Cd­(H2L)­(SO4)2­(H2O)2]n­·6nH2O (2), [CdL­(malonate)]n­·5nH2O (3), [Cd2L­(malonate)­Cl2(H2O)]n­·nH2O (4), [Cd2(H2L)­(succinate)3]n­·4nH2O (5), [Cd2L­(fumarate)2­(H2O)2]n­·2nH2O (6), [Cd2L­(m-BDC2–)2]n­·2nH2O (7), [Cd2(L)­(p-BDC2–)2­(H2O)3]n­·3nH2O (8), [Cd3(L)2­(p-BDC2–)3­(H2O)4]n­·nH2O (9), and [Cd3(H2L)­(p-BDC2–)2­(SO4)2­(H2O)3]n­·2nH2O (10) (L = N,N′-bis­(pyridin-3-ylmethyl)­ethane-1,2-diamine, m-BDC2– = m-benzene dicarboxylate dianion, p-BDC2– = p-benzene dicarboxylate dianion), which have been characterized by elemental analysis, infrared, thermogravimetric analysis, PL, powder and single-crystal X-ray diffraction. Structural analyses indicate that the diverse coordination modes of the bis­(pyridyl) ligand with a chelated or protonated spacer, the feature of different inorganic and organic anions, can effectively influence the topological structures of these complexes. Complex 1 presents a three-dimensional (3D) hybrid network which is accomplished by the interconnection of adjacent Cd­(II) cations through L molecules and μ2-Cl anions. Complex 2 exhibits an interesting pseudo 2-fold interpenetrated network formed by the interconnection of a [Cd-H2L2+]n pcu net and [SO42+-H2O]n pcu net. In complexes 3 and 4, adjacent Cd­(II) cations are all bridged by dicarboxylate and L to generate a sql layer. In contrast, complex 5 presents 3-fold parallel interpenetrated sql layer owing to the protonated spacer of H2L2+ cation which extends the size of the quadrate window. The organic dicarboxylates in complexes 6 and 7 present more abundant coordination modes which join adjacent Cd­(II) cations together with L molecules, thus giving rise to a different 3D framework with sra and snk topology. The p-BDC2– dianions in complexes 8, 9, and 10 present different coordination modes and join adjacent Cd­(II) cations together with L molecules and H2L2+ cations to form a diverse ladder chain, tfc and new (44.611)­(66) topology. Luminescent investigation reveals that the emission maximum of these 10 complexes varies from 376 to 450 nm.