Solvent Effects on Cyanine Derivatives: A PCM Investigation

In this work, we present time-dependent density functional theory calculations of the excited-state geometries and electronic properties of both model cyanines and BODIPY derivatives, which are particularly challenging dyes for theoretical chemistry. In particular, we focus on environmental effects, using a panel of approaches derived from the polarizable continuum model, including full corrected linear response (cLR) values determined through a very recently developed approach. It turns out that in idealized quasi-linear cyanines, all approaches provide very similar excited-state geometries though linear response (LR), and cLR models yield very different transition energies. For the fluoroborate derivatives, LR apparently overestimates the planarity of the excited-state geometries, and cLR optimizations yield slightly smaller fluorescence energies than LR, making these values closer to experimental references. The computed corrections are however too small to explain (taken alone) the significant theory/experiment discrepancies.