Electron transfer through bridging molecular structures

Pairs of reducible pentakis(thiophenyl)benzene subunits are linked by different molecular structures as model compounds for reducible molecular-wire-type synthons showing varying electron-transfer ability as a function of the bridging structures, consisting of either para-divinylbenzene, bis-hydrazone, or diacetylene. Their electron-transfer ability from one reducible subunit to the other was investigated by electrochemical and spectroelectrochemical methods. In the case of the bis-hydrazone bridge and the diacetylene bridge, the solid-state structures support the experimental findings. While the para-divinylbenzene bridge completely isolates the reducible subunits (class I system) the diacetylene bridge electronically connects the two reducible structures (class III system), demonstrating its potential application as a "molecular wire." The bis-hydrazone linked dimer displays electronic communication only to a small extend, which was only observed in the spectroelectrochemical investigation. The diacetylene connection as active electron-transfer linker together with poly(thiophenyl)benzene as reducible subunits was used to design more complex molecular architectures. Linear rodlike structures did allow adjustment of the length of these type of molecular wires and investigation of the extent of electron mobility. Cyclic structures addressed the possibility of moving electrons on a bent molecular wire.