Abstract
The photophysical properties of some monomeric and dimeric BODIPY systems were investigated at the density functional theory level and herein reported. In particular, the absorption spectra were fully characterized, low energy singlet and triplet excited states were discussed also focusing on the energy difference gaps between them and computing the spin-orbit couplings values for the possible intersystem crossing channels. The heavy atom effect of iodine substituents on the photophysical properties of a monomer and on a dimer under investigation was also estimated. Results obtained on the considered compounds allow us to predict which is the most promising candidate to be suggested as a photosensitizer in photodynamic therapy.
Highlights
In the last decade the BF2-chelated dipyrromethenes, known as BODIPYs, have been proposed for many applications in materials science and biotechnology because of their excellent stability, arising from the strongly electron-withdrawing BF2 group, intense absorption band in the near-infrared region, sharp emissions and quantum fluorescence yields [1,2,3]
The first strategy exploits the heavy atoms to enhance the efficiency of the intersystem crossing whose constant depends on the amplitude of the spin-orbit couplings between the singlet and triplet states
The computed time-dependent formulation (TDDFT) excitation energies for singlet and triplet states are collected in Table 2 together with the available experimental and previous theoretical results
Summary
In the last decade the BF2-chelated dipyrromethenes, known as BODIPYs, have been proposed for many applications in materials science and biotechnology because of their excellent stability, arising from the strongly electron-withdrawing BF2 group, intense absorption band in the near-infrared region, sharp emissions and quantum fluorescence yields [1,2,3]. We determined the geometries of ground and excited states, the absorption features, the singlet-triplet energy gaps, and the spin orbit coupling matrix elements. Spin–orbit matrix elements were computed with DALTON code [26] by using B3LYP functional and cc-pVDZ basis set for all the atoms except iodine, for which the coupled pseudopotential was considered.
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