Accurate Vertical Excitation Energies of BODIPY/Aza-BODIPY Derivatives from Excited-State Mean-Field Calculations

Abstract

We report a benchmark study of vertical excitation energies and oscillator strengths for the HOMO → LUMO transitions of 17 boron-dipyrromethene (BODIPY) structures, showing a large variety of ring sizes and substituents. Results obtained at the time-dependent density functional theory (TDDFT) and at the delta-self-consistent-field (ΔSCF) by using 13 different exchange correlation kernels (within LDA, GGA, hybrid, and range-separated approximations) are benchmarked against the experimental excitation energies when available. It is found that the time-independent ΔSCF DFT method, when used in combination with hybrid PBE0 and B3LYP functionals, largely outperforms TDDFT and can be quite competitive, in terms of accuracy, with computationally more costly wave function based methods such as CC2 and CASPT2.

Figure 1

Structure of 8-H-BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) together with a numbering scheme. The meso position is position 8. C atoms are in black color, N atoms in blue, H atoms in white, B atoms in orange, and F atoms in green.

Figure 2

Chemical structures of BODIPYs and aza-BODIPYs considered in this work. Reprinted with permission from ref (39). Copyright 2015 American Chemical Society. The numbering follows that adopted by Momeni and Brown.

Figure 3

Comparison between ΔSCF calculated vertical excitation energies and experimental excitation energies of the set of molecules (4 is excluded) investigated in this work. Left panel: PBE0 xc potential. Right panel: B3LYP xc potential.

Figure 4

Conjugated BODIPYs and aza-BODIPYs considered in this work. Reprinted with permission from ref (40). Copyright 2021 Wiley.