Strategies towards enhancing the efficiency of BODIPY dyes in dye sensitized solar cells

Synthesis and Photophysical Characterizations of Benzimidazole Functionalized BODIPY Dyes

Herein, a series of new BODIPY dyes substituted by 2-phenyl benzimidazole units at the meso (C8) position including methyl/ethyl, phenyl, or p-methoxyphenyl moieties at the distal and proximal positions of the BODIPY core have been successfully synthesized and their photophysical characteristics were analyzed. Experimentally investigating absorption and fluorescence profiles in the THF media was followed by density functional theory (DFT) calculations to clarify photophysical features. Theoretical analyses have revealed that upon excitation, both electrons and holes are confined solely within the BODIPY core. The energy levels of the frontier molecular orbitals converge depending on the presence of the phenyl and p-methoxyphenyl substituents. The orbital distributions of both electron and hole were in the -3 and -5 positions, which demonstrates a continuous conjugation with the BODIPY core at these sites. However, the electron density present on the phenyl rings located at the -1, -7, and -8 (meso) positions was found to be negligible. The benzimidazole-BODIPYs exhibited photodynamic activity (Φ∆) ranging from ~ 7% to ~ 11%, determined by a comparative method. Moreover, the compounds have shown to maintain their stability thermally in a non-reactive/inert environment up to temperatures surpassing 300 °C, exhibiting primarily a two-phase decomposition process. These compounds have the potential to function as antibacterial and anti-biofilm agents when used in concentrations ranging from 0.5 to 2.0 mg/mL. The results provide a basis for evaluating heterocyclic benzimidazole units on photophysical processes containing BODIPY chromophores.

Mitochondria-targeted biotin-conjugated BODIPYs for cancer imaging and therapy

Two BODIPY-biotin conjugates KDP1 and KDP2 are designed and synthesized for targeted PDT applications. Both have good absorption with a high molar absorption coefficient and decent singlet oxygen generation quantum yields. The photosensitizers KDP1 and KDP2 were found to be localized in the mitochondria with excellent photocytotoxicity of up to 18.7 nM in MDA-MB-231 breast cancer cells. The cell death predominantly proceeded through the apoptosis pathway via ROS production.

Accurate predictions of the electronic excited states of BODIPY based dye sensitizers using spin-component-scaled double-hybrid functionals: a TD-DFT benchmark study

The vertical excitation energies of 13 BODIPY based dye sensitizers are benchmarked by means of TD-DFT, using 36 functionals from different DFT rungs. Most TD-DFT results were found to overestimate the excitation energies, and show mean absolute error (MAE) values in the range 0.2–0.5 eV. The dispersion-corrected, spin-component-scaled, double-hybrid (DSD) functionals DSD-BLYP and DSD-PBEP86 were found to have the smallest MAE values of 0.083 eV and 0.106 eV, respectively, which is close to the range of average errors found in the more expensive coupled-cluster methods. Moreover, DSD-BLYP and DSD-PBEP86 functionals show excellent consistency and quality of results (standard deviation = 0.048 eV and 0.069 eV respectively). However, the range separated hybrid (RSH) and the range separated double hybrid (RSDH) functionals were found to provide the best predictability (linear determination coefficient R² > 0.97 eV).

The excitation energies of 13 BODIPY dye sensitizers are benchmarked by means of TD-DFT, using 36 functionals. Spin-component-scaled double-hybrid (DSD) functionals are found to show the best performance.

Synthesis and photophysical properties of novel oxadiazole substituted BODIPY fluorophores

Using 3-phenyl-5-(5-phenyl-1H-pyrrol-3-yl)-1,2,4-oxadiazole, BODIPYs with the oxadiazole groups at the 1,7-positions were prepared and their photophysical properties were characterized.