Fluorescent coordination polymeric gel from tartaric acid-assisted self-assembly.

A fluorescent organogel is obtained from the reaction of Zn(OAc)(2) x 2 H(2)O, 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (bpd), and tartaric acid (H(4)tar) in methanol. The gel is proposed to have formed by the cross-linking of linear 1D coordination polymers Zn(bpd) with tartarate coligand in a highly random fashion which entrapped the solvent molecules through hydrogen-bonding interactions between the tar coligand and solvent molecules. Higher dimensional coordination polymeric structure is proposed for this gel based on the corresponding complexes formed by oxalic and succinic acids. The presence of three components is essential for the gelation. Interestingly, organogelation of the coordination polymer has induced remarkable fluorescence properties in the weakly emissive bpd. Such fluorescence enhancement is attributed to the reduction in nonradiative decay in the aggregated state. The organogel exhibits viscoelastic behavior as evidenced from the rheological studies.