A straightforward method to quantify the electron-delocalizing ability of pi-conjugated molecules

Electronic delocalization is essential to the properties of pi-conjugated molecules. We introduce the inter-fragment delocalization index (IFDI) as an easy-to-use computational method for quantifying the electronic delocalization in pi-conjugated oligomers and molecular wire models. We show that the IFDI is related to the torsion barriers of pi-conjugated dimers, and to the single-molecule conductance of several pi-conjugated fragments. The IFDI is a useful screening technique for comparing different pi-conjugated subunits as components in organic electronics, since it can quantify the influence of substitution position, structure, and (anti)aromaticity on delocalization.