The syntheses and physicochemical properties for a series of 2,6-disubstituted-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes are reported. The use of chromophores or redox active species as π-spacers, such as BODIPY, requires the inclusion of a sufficiently conjugated donor in order to achieve appropriate charge separation upon photoexcitation. The information derived from this study offers guiding principles for incorporating strongly absorbing, non-innocent π-spacers in organic dye design.

Fluoride abstraction from a BODIPY dye gives a well defined borenium ion which can be converted to a borenium hydride via treatment with DIBAL-H.

Reaction of the dipyrrin ligand 1,3,7,9-tetramethyl-2,8-diethyldipyrrin with BH 3 3 SMe 2 initially gives a dipyrrin-BH 3 adduct, which eliminates dihydrogen to form the dipyrrin-supported BH 2 borane L H BH 2 . This species is unstable toward isomerization to its dipyrromethane isomer 1, via a (possibly BH 3 catalyzed) hydride transfer from boron to the meso position of the dipyrrin core. Computations suggest that 1 is ∼4 kcal mol -1 more stable than the dipyrrin isomer. These conclusions were supported by low-temperature NMR and UV-vis/fluorescence spectroscopic experiments and labeling studies using BD 3 3 SMe 2 . Borane 1 is susceptible to hydride abstraction to form the previously characterized borenium ion [L H BH][B(C 6 F 5 ) 4 ] and takes up hydride to form a dipyrromethane borohydride, which was characterized spectroscopically and crystallographically.

A family of five axial aryl-substituted boron subphthalocyanine (BsubPc) derivatives bearing a hydrido, methyl, methoxy, phenyl, or fluoro substituent at the para position of the aryl were synthesised from Br-BsubPc and the corresponding aryl Grignard reagent in moderate yields. The physicochemical characterisation of these derivatives gave similar absorption, photoluminescence, and cyclic voltammetry profiles and photoluminescence quantum yields, indicating that the nature of the substituent at the para position does not influence the basic photophysical properties of this generic class of BsubPcs. Conversely, the solid-state structural arrangement obtained from single crystals is highly dependent on the para substituent; for the non-polar hydrido, methyl, and phenyl substituents, only concave isoindole π interactions are present. Substitution for the polar methoxy or fluoro ligand affords one-dimensional ribbons formed by convex π interactions, where these ribbons further interact through concave isoindole π interactions with the adjacent ribbon, creating an extended two-dimensional π network. On incorporation of the hydrido, methyl, and fluoro derivatives into organic photovoltaic (OPV) devices, similar results and device metrics were obtained with the methyl and fluoro derivatives. Both, however, were significantly outperformed by the hydrido derivative. The uniqueness of the hydrido derivative is only realised once incorporated into OPVs as it shares the same basic physical properties as the other derivatives. Given these findings, we identify the hydrido derivative as the aryl-BsubPc with the most promise for future work in OPVs.

A methodology for the incorporation of fluoroaryl groups into boron dipyrrinato complexes (modified BODIPY dyes) is reported. Two hexaalkylated dipyrrinato ligands with either H or CH 3 occupying the meso position were employed; when they were treated with fluoroaryl haloboranes in the presence of a weak base, the title compounds were prepared in good to excellent yields. The structures of seven derivatives were determined using X-ray crystallography, and their spectroscopic, photophysical, and redox properties are compared.