Excited-state nature in benzodifuranone dyes: Insights from ab initio simulations

Using ab initio theoretical tools simultaneously accounting for electron correlation and environmental effects, we have simulated the optical spectra of benzodifuranone dyes. In a first step, a valuable computational protocol has been defined and it turned out that a PCM-TD-M06-2X/6-311+G(2d,p)//PCM-PBE0/6-311G(d,p) approach provides an adequate balance between computational requirements and accuracy (deviations of ca. 10 nm with respect to experiment). In a second stage, we have calculated the spectrum of a large series of push-pull structures, and it turned out that the benzodifuranone core is a strong electron capturing group at the excited-state. Indeed, strong auxochroms like the nitro and cyano groups fall short to significantly perturb the LUMO of this series of chromogens. Eventually, in a last phase, the implications of these results are discussed for a series of organic dyes of potential interest for solar cells (DSSC).