BODIPY–Hexaphyrin Hybrids

Porphyrin-Ryleneimide Hybrids: Low-Bandgap Acceptors in Energy-Transfer Cassettes

Energy-transfer cassettes consisting of naphthaleneimide-fused metalloporphyrin acceptors (M=Zn and Pd) and BODIPY donors have been designed and synthesized. These systems have rigid pseudo-tetrahedral structures with a donor-acceptor separation of ca. 17.5 Å. Spectroscopic investigations, including femtosecond transient absorption measurements, showed efficient excitation energy transfer (EET) occurring according to the Förster mechanism. Strong fluorescence of the donor units and significant spectral overlap of the donor and acceptor subunits are prerequisites for the efficient EET in these systems.

Nucleophilic Aromatic Substitution on Pentafluorophenyl-Substituted Dipyrranes and Tetrapyrroles as a Route to Multifunctionalized Chromophores for Potential Application in Photodynamic Therapy

The application of porphyrinoids in biomedical fields, such as photodynamic therapy (PDT), requires the introduction of functional groups to tune their solubility for the biological environment and to allow a coupling to other active moieties or carrier systems. A valuable motif in this regard is the pentafluorophenyl (PFP) substituent, which can easily undergo a regiospecific nucleophilic replacement (S_N Ar) of its para-fluorine atom by a number of nucleophiles. Here, it is shown that, instead of amino-substitution on the final porphyrinoid or BODIPY (boron dipyrromethene), the precursor 5-(PFP)-dipyrrane can be modified with amines (or alcohols). These dipyrranes were transformed into amino-substituted BODIPYs. Condensation of these dipyrranes with aldehydes gave access to trans-A₂ B₂ -porphyrins and trans-A₂ B-corroles. By using pentafluorobenzaldehyde, it was possible to introduce another para-fluorine atom, which enabled the synthesis of multifunctionalized tetrapyrroles. Furthermore, alkoxy- and amino-substituted dipyrranes were applied to the synthesis of A₃ B₃ -hexaphyrins. The polar porphyrins that were prepared by using this method exhibited in vitro PDT activity against several tumor cell lines.

Design, synthesis and photophysical studies of dipyrromethene-based materials: insights into their applications in organic photovoltaic devices

This review article presents the most recent developments in the use of materials based on dipyrromethene (DPM) and azadipyrromethenes (ADPM) for organic photovoltaic (OPV) applications. These chromophores and their corresponding BF2-chelated derivatives BODIPY and aza-BODIPY, respectively, are well known for fluorescence-based applications but are relatively new in the field of photovoltaic research. This review examines the variety of relevant designs, synthetic methodologies and photophysical studies related to materials that incorporate these porphyrinoid-related dyes in their architecture. The main idea is to inspire readers to explore new avenues in the design of next generation small-molecule and bulk-heterojunction solar cell (BHJSC) OPV materials based on DPM chromophores. The main concepts are briefly explained, along with the main challenges that are to be resolved in order to take full advantage of solar energy.