Improving the Accuracy of Excited-State Simulations of BODIPY and Aza-BODIPY Dyes with a Joint SOS-CIS(D) and TD-DFT Approach

Abstract

BODIPY and aza-BODIPY dyes constitute two key families of organic dyes with applications in both materials science and biology. Previous attempts aiming to obtain accurate theoretical estimates of their optical properties, and in particular of their 0-0 energies, have failed. Here, using time-dependent density functional theory (TD-DFT), configuration interaction singles with a double correction [CIS(D)], and its scaled-opposite-spin variant [SOS-CIS(D)], we have determined the 0-0 energies as well as the vibronic shapes of both the absorption and emission bands of a large set of fluoroborates. Indeed, we have selected 47 BODIPY and 4 aza-BODIPY dyes presenting diverse chemical structures. TD-DFT yields a rather large mean signed error between the experimental and theoretical 0-0 energies with a systematic overshooting of the transition energies (by ca. 0.4 eV). This error is reduced to ca. 0.2 [0.1] eV when the TD-DFT 0-0 energies are corrected with vertical CIS(D) [SOS-CIS(D)] energies. For BODIPY and aza-BODIPY dyes, both CIS(D) and SOS-CIS(D) clearly outperform TD-DFT. The present computational protocol allows accurate data to be obtained for the most relevant properties, that is, 0-0 energies and optical band shapes.

Photophysics of BODIPY Dyes as Readily-Designable Photosensitisers in Light-Driven Proton Reduction

“…This overestimation of the excitation energies is reasoned by the lack of TDDFT to address the multi-configurational character and by the inability to describe double excitations (DE). Typically, for BODIPY dyes, TDDFT overestimates the excitation energy of the bright absorption band [30][31][32][33] (measured in THF) in the visible region centred at 497 nm (2.49 eV), assigned to the excitation into the S 1 state at 419 nm (2.96 eV), by approximately 0.5 eV, similar hypsochromic shifts were observed for the UV bands (see states S 2 -S 4 in Table S2). This overestimation of the excitation energies is reasoned by the lack of TDDFT to address the multi-configurational character and by the inability to describe double excitations (DE).…”

“…Assessing excited state properties by virtue of computationally affordable time-dependent density functional theory (TDDFT) simulations is a well-known challenge for BODIPY dyes [30][31][32][33]. Therefore, following the computational protocol presented in [33], the fully-relaxed (singlet) ground state equilibrium structure of 2 was obtained using the hybrid-functional PBE0 [45][46][47] and the cc-pVTZ triple-ξ basis set [48,49] as implemented in the Gaussian 09 program [50], while effects of interaction with the THF solvent (ε = 7.4257, n = 1.4070) were taken into account by the integral equation formalism of the polarizable continuum model (IEFPCM) [51].…”

Computational Molecular Electronic Spectroscopy with TD-DFT

“…In the protocol proposed by Goerigk and Grimme [13], the experimental 0-0 energies are first transformed into "experimental" vertical energies by applying successive corrections for solvation, vibration, and geometrical reorganization effects determined with TD-DFT. Alternatively, one can determine AFCP energies through (10) and next correct them through wavefunction (Ψ) vertical calculations performed on the DFT GS and TD-DFT ES geometries [46,47]. For approaches that can only be used for gas-phase vertical transition energies, the corrected AFCP energy simply becomes Computational Molecular Electronic Spectroscopy with TD-DFT…”

“…The fundamental reasons explaining this failure of TD-DFT have been given in [90-92, 94, 95] and summarized in a recent account [93]. A pragmatic approach to obtain accurate E AFCP is to apply (13) selecting an appropriate variant of the CIS(D), ADC(2) or CC2 approaches as the wavefunction method [47,96]. Examples of applications of such mixed approach are given in Sect.…”

Computational Design of Molecular Motors and Excited-State Studies of Organic Chromophores

“…However, some notable contributions to this field have been made by Grimme 88 and Jacquemin [89][90][91][92] and their coworkers, who aimed to simplify the calculation of 0−0 excitation energies (ΔE 00 , i.e., energy differences between ground and excited states in their lowest vibrational levels) using composite procedures. These procedures combined geometries and zero-point vibrational energy (ZPVE) corrections obtained from TD-DFT calculations with transition energies from wavefunction-based methods such as CIS(D) and CC2.…”