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

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