Effect of meso-substituents on the electronic transitions of BODIPY dyes: DFT and RI-CC2 study.

In this work, the influence of substituents on the electronic transitions of model 8-R-BODIPY dyes (R=NMe2, NH2, OH, CH3, H, F, SH, Cl, Br, CF3, CN, and NO2) was investigated theoretically using time-dependent density functional theory (TD-DFT) and ab initio coupled-cluster doubles (CC2) quantum chemical calculations. Quantum chemical modeling shows a direct relationship between the electron donating and electron withdrawing character of substituents expressed by Hammett substituent constants (σp) and changes in energy of the HOMO-LUMO gap modulating spectral shifts of the S0→S1 transition. Good linear correlations of the calculated LUMO energies and σp as well as the shape of the HOMO and LUMO allow to obtain a reasonable explanation for the observed effects of substituents.