Sharp Turns And Fluorescent Repeats: Modular Construction And Shape-Dependent Electronic Properties Of Pi-Conjugated Chain Molecules

In search of the design rules for structural ordering of open-chain molecules, we have built a series of zig-zag shaped pi-conjugated structures with ring-fused heteroaromatics as sharp turns and tolane-based linear fragments as light-emitting units. Using only a finite number of common building blocks, an efficient "double-elongation" strategy was implemented to construct a series of pi-conjugated oligomers with precise length control (55-89 % yields). Our approach takes advantage of the modular nature of the bis(triazolo)benzene synthesis and the masked reactivity of the nitro group. A combination of photophysical and DFT computational studies revealed that the bis(triazolo)benzene-tolane repeat units behave as electronically decoupled light-absorbing/emitting units (lambda(max,em) = 408-422 nm; phi(F) = 20-25 % in THF). Such context-independent photophysical properties promise their potential applications in chemical sensing and switching.