Metal-directed self-assembly: Two new metal-binicotinate grid polymeric networks and their fluorescence emission tuned by ligand configuration

Two new 2-D metal-binicotinate coordination polymers, namely, [Cd-II{bpdc}](n) (1) and {[Zn-8(II)(bpdc)(8)(H2O)(8)](H2O)(8)}(n) (2) (H(2)bpdc = binicotinic acid) have been synthesized using hydrothermal and three-layer diffusion methods, respectively. Single-crystal X-ray analyses revealed that both are extended grid networks of the (4,4) topology. Their structures alter with the configuration and function of bpdc. The achiral, free H2bpdc has axial chirality induced by metal coordination in 1, and bpdc connects to four metal centers forming a 2-D (4,4) net with three kinds of apertures generated through self-assembly. In 2, however, bpdc connects to three metal centers, fabricating a microporous framework containing hydrophilic channels. Studies on the solid emission spectra of the free ligand, 1, and 2 confirmed, that the configuration of bpdc resulting from metal-directed coordination has a profound effect on the fluorescence emissions of 1 and 2. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).