Structural diversity and properties of Zn(II) and Cd(II) complexes with a flexible dicarboxylate building block 1,3-phenylenediacetate and various heterocyclic co-ligands.

A series of Zn(II) and Cd(II) complexes with a flexible dicarboxylate building block and various heterocyclic co-ligands, formulated as {[Zn(2)(pda)(2)(phen)(2)].2H(2)O}(n) (1), {[Zn(pda)(dpe)].H(2)O}(n) (2), [Zn(pda)(bpp)](n) (3), {[Cd(2)(pda)(2)(2,2'-bipy)(2)].2H(2)O}(n) (4), {[Cd(pda)(4,4'-bipy)(H(2)O)].H(2)O}(n) (5) and {[Cd(2)(pda)(2)(bpp)(3)].14H(2)O}(n) (6) (pda = 1,3-phenylenediacetate, phen = 1,10-phenanthroline, dpe = 1,2-di(4-pyridyl)ethylene, bpp = 1,3-bi(4-pyridyl)propane, 2,2'-bipy = 2,2'-bipyridine, and 4,4'-bipy = 4,4'-bipyridine), have been synthesized and structurally characterized. In 1, the (H(2)O)(8) clusters interlink the cyclic coordination dimers to give a 3D network through hydrogen bonding. Both 2 and 3 feature 2D corrugated (4,4) layers, which are of 2-fold interpenetrating for 3. In 4, the dimeric Cd(II) subunits are connected by the 1,3-pda ligands to generate a rampart-shaped 1D chain motif. As for 5, the [Cd(pda)](2) rings are connected by the paired 4,4'-bipy ligands to afford a tube-shaped 1D motif. In contrast to 1-5, complex displays a 3D diamond network and, interestingly, the T5(0)A(0)A(2) water tapes are found to locate in the channels of this 3-D array. A structural comparison of these complexes demonstrates that the characteristics of auxiliary ligands (from chelating to bridging) play a key role in governing the coordination motifs as well as the 3-D supramolecular lattices. Solid-state properties such as photoluminescence and thermal stability of 1-6 have also been studied.