The reactions of N,N′-di(3-pyridyl)adipoamide (L) with the corresponding silver(I) salts afforded the complexes {[Ag(L)](PF 6 )·2CH 3 CN} ∞ , 1, {[Ag(L)](BF 4 )· CH 3 CN} ∞ , 2, {[Ag(L)](NO 3 )·CH 3 CN} ∞ , 3, {[Ag(L)](PF 6 )· 4DMF} ∞ , 4, {[Ag(L)](BF 4 )·4DMF} ∞ , 5, {[Ag(L)](CF 3 SO 3 )· DMF} ∞ , 6, {[Ag(L)](ClO 4, 9, and [Ag(L)(p-TsO)] ∞ , 10. Complex 1 forms a one-dimensional (1D) concavo-convex chain, and complexes 2, 3, 6, and 7 show 1D polymeric pairs of zigzag chains supported by the Ag---Ag and π−π interactions, whereas complexes 4, 5, and 8 adopt zigzag chains. Complex 9 forms a zero-dimensional (0D) dinuclear metallocycle, and complex 10 shows a two-dimensional (2D) pleated grid with a {4,8 2 } topology, respectively. The L ligands in these complexes adopt various ligand conformations, which are subjected to the changes of the counteranions and solvents, resulting in the different structural types. Reversible crystal-to-crystal transformation was observed in 7 and 8 upon removal and uptake of the acetonitrile molecules, while the process was irreversible in 9 and 10, which is concomitant with changes in supramolecular structures, ligand conformations, and luminescent properties. The main driving forces for the structural transformations are the Ag---N and Ag---O interactions. ■ INTRODUCTIONThe rational design and synthesis of novel coordination polymers continue to be an active area of investigation because it expands the range of new complexes with preselected physical and chemical properties. 1 The range and variety of the selfassembling structures that can be constructed rely on the presence of suitable metal−ligand interactions and supramolecular contacts, that is, hydrogen bonding and other weak interactions. 2 Additionally, the structural types of the resulting coordination polymers are also affected by factors such as counterion, 3 metal-to-ligand ratio, 4 and solvent. 5 The networks of coordination polymers containing flexible bidentate ligands are less predictable due to the possible occurrence of supramolecular isomerism involving the adoption of different ligand conformations. 6 It has been shown that 1,2-bis(4-pyridyl)ethane can adopt either a gauche or anti geometry, and 1,3-bis(4-pyridyl)propane can exist in anti-anti, gauche-anti, and gauche− gauche conformations. However, the use of conformationally flexible ligands may provide unique opportunities to construct novel crystalline architectures with desirable characteristics. 6f We have recently investigated the roles of ligand conformations of the flexible dipyridyl ligands bearing amide groups in the structural diversity, 7 and reported a series of one-dimensional (1D) silver(I) coordination polymers containing the flexible ligand N,N′-di(2-pyridyl)adipoamide (L′), 7a involving the zigzag chains [Ag(L′)(NO 3 )] ∞ , [Ag(L′)(PF 6 )] ∞ , [Ag(L′)(BF 4 )-(CH 3 CN)(H 2 O) 0.5 ] ∞ , and [Ag(L′)(ClO 4 )(CH 3 CN)] ∞ , the helical chain [Ag(L′)(ClO 4 )(H 2 O) 0.67 ] ∞ , and the sinusoidal chain [Ag 2 (L′) 2.5 SO 4 ] ∞ , which demonstrates an un...

By using isomeric N,N′-di(2-pyridyl)adipoamide (L 1 ), N,N′-di(3-pyridyl)adipoamide (L 2 ) and N,N′-di(4-pyridyl)adipoamide (L 3 ) and isomeric 1,2-benzenedicarboxylic acid (1,2-H 2 BDC), 1,3-benzenedicarboxylic acid (1,3-H 2 BDC) and 1,4-benzenedicarboxylic acid (1,4-H 2 BDC), eight Zn(II) and Cd(II, have been synthesized under hydrothermal conditions. Complexes 1, 4, and 5 form 1D double-looped chain, 1D chain with loops and 2D layer with loops, respectively, and complex 6 exhibits a 1D ladder chain. Complex 2 shows rare 3-fold interpenetrated hcb layers, in which each layer interdigitates with other four parallel layers by directing the 1,3-BDC ligands into the windows of the adjacent nets, whereas complexes 3 and 8 forms planar and undulated hcb layers, respectively. Complex 7 shows a 3D selfpenetrating net of {4 24 .5.6 3 }-ilc topology with a unique arrangement for the L 2 spacer ligands. The L 1 ligands in complexes 3 and 8 adopt the new tetradentate bonding mode involving chelation and bridge through two pyridyl nitrogen atoms and two amide oxygen atoms, whereas the L 2 and L 3 ligands in other complexes show the bidentate bonding mode through the two pyridyl nitrogen atoms. The various bonding modes and the ligand-isomerism of the spacer ligands BDC 2− and L 1 −L 3 as well as the identity of the metal center play important roles in determining the structural diversity.

A series of Zn(II) complexes with N,N 0 -di(4-pyridyl)adipoamide ligands, {[ZnX 2 (L)]$H 2 O} N (X ¼ Cl, 1, Br, 2 and I, 3; L ¼ N,N 0 -di(4-pyridyl)adipoamide), [Zn 2 X 4 (L) 2 ]$2DMF (X ¼ Cl, 4 and Br, 5) and [Zn 2 I 4 (L) 2 ]$4DMF$C 4 H 10 O, 6, were prepared and their structures determined by X-ray crystallography. Complexes 1 and 2 form double-stranded helical chains which are supported by the N-H/O and O-H/X hydrogen bonds involving the guest water molecules and the halide anions, whereas 3 shows sinusoidal chains which are interlinked by the N-H/O hydrogen bonds and p-p interactions. Complexes 1-3 represent a unique example that the halide anions show significant effect on folding and unfolding of the Zn(II) double-stranded helical coordination polymers. Complexes 1-3 can be transformed to the corresponding complexes 4-6, which are dinuclear with 34-membered metallocycles. In these complexes, the chloride and bromide anions play the same role in the crystal structures, while the iodide anion is distinct.

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Structure-directing roles of auxiliary polycarboxylate ligands in the formation of Zn(II) and Cd(II) coordination polymers based on a flexible N,N9-di(3pyridyl)dodecanediamide3