Variations of structures and solid-state conductivity of isomeric silver(I) coordination polymers having linear and V-shaped thiophene-centered ditriazole ligands

A pair of new linear and V-shaped acceptor-donor-acceptor (A-D-A) thiophene-centered ditriazole structural isomers, i.e., 2,5-di(1H-1,2,4-triazol-1-yl)thiophene (L-1) and 3,4-di(1H-1,2,4-triazol-1-yl)thiophene (L-2), has been synthesized and characterized. They are used as mu(2)-bridging ligands to prepare a pair of silver(I) coordination polymers formulated as [Ag(L-1)(NO3)](n) (1) and [Ag(L-2)(NO3)](n) (2), which are also structural isomers at the supramolecular level. X-ray single-crystal diffraction analyses for 1 and 2 reveal that they exhibit the same one-dimensional (1D) coordination polymers but different structural architectures because of the distinguishable shape and configuration of isomeric ligands (L1 and L2) and the alterations of the coordination numbers. More interestingly, compared with the free ligands, 1D silver(I) polymeric isomers 1 and 2 show significant enhancement of solid-state conductivity to different extents (1.42 x 10(4) and 2.17 x 10(3) times), where 6.96 times' enhancement of solid-state conductivity from 1 to 2 has been observed. The formation of Ag-N coordinative bonds and the configurational discrepancy of L1 and L2 are believed to play important roles in facilitating the electron transport between molecules, which can also be supported by Density Function Theory calculations of their band gaps. (C) 2014 Elsevier Inc. All rights reserved.