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The search for long‐lived red and NIR fluorescent dyes is challenging and hitherto scarcely reported. Herein, the viability of aza‐BODIPY skeleton as a promising system for achieving thermal activated delayed fluorescent (TADF) probes emitting in this target region is demonstrated for the first time. The synthetic versatility of this scaffold allows the design of energy and charge transfer cassettes modulating the stereoelectronic properties of the energy donors, the spacer moieties and the linkage positions. Delayed emission from these architectures is recorded in the red spectral region (695–735 nm) with lifetimes longer than 100 μs in aerated solutions at room temperature. The computational‐aided photophysical study under mild and hard irradiation regimes disclose the interplay between molecular structure and photonic performance to develop long‐lived fluorescence red emitters through thermally activated reverse intersystem crossing. The efficient and long‐lasting NIR emission of the newly synthesized aza‐BODIPY systems provides a basis to develop advanced optical materials with exciting and appealing photonic response. [ABSTRACT FROM AUTHOR]

This minireview is devoted to honoring the memory of Dr. Thomas Dougherty, a pioneer of modern photodynamic therapy (PDT). It compiles the most important inputs made by our research group since 2012 in the development of new photosensitizers based on BODIPY chromophore which, thanks to the rich BODIPY chemistry, allows a finely tuned design of the photophysical properties of this family of dyes to serve as efficient photosensitizers for the generation of singlet oxygen. These two factors, photophysical tuning and workable chemistry, have turned BODIPY chromophore as one of the most promising dyes for the development of improved photosensitizers for PDT. In this line, this minireview is mainly related to the establishment of chemical methods and structural designs for enabling efficient singlet oxygen generation in BODIPYs. The approaches include the incorporation of heavy atoms, such as halogens (iodine or bromine) in different number and positions on the BODIPY scaffold, and also transition metal atoms, by their complexation with Ir(III) center, for instance. On the other hand, low‐toxicity approaches, without involving heavy metals, have been developed by preparing several orthogonal BODIPY dimers with different substitution patterns. The advantages and drawbacks of all these diverse molecular designs based on BODIPY structural framework are described. [ABSTRACT FROM AUTHOR]

In this article the design and characterization of a set of novel red‐light‐emitting laser aza‐BODIPY dyes is reported. The applied synthetic method allows an exhaustive and versatile functionalization of both the dipyrrin core and the boron bridge. From the analysis of the photophysical and laser signatures, we determine the suitable modifications of the chromophoric backbone necessary to modulate the emission spectral region, efficiency and photostability under a strong irradiation regime. These dyes are endowed with efficient fluorescence and laser emission, and are particularly outstanding in terms of their high photostability, a key parameter to guarantee long‐lasting emission in any (bio)technological application. The herein‐reported results support, for the first time, the viability of aza‐BODIPYs as tunable red laser dyes. In fact, the laser performances of some of the tested aza‐BODIPYs surpass those of commercially available laser dyes in the same spectral region. Live long and glow: From the conducted computationally aided photophysical properties and the recording of the laser signatures, the structural guidelines which rule the emission properties of aza‐BODIPYs are determined. Some of the reported dyes display tunable, efficient and photostable laser emission at the red edge, surpassing the performance of commercially available laser dyes in this spectral window. [ABSTRACT FROM AUTHOR]

The synthesis, photophysical characterization, and modeling of a new library of halogen-free photosensitizers (PS) based on orthogonal boron dipyrromethene (BODIPY) dimers are reported. Herein we establish key structural factors in order to enhance singlet oxygen generation by judiciously choosing the substitution patterns according to key electronic effects and synthetic accessibility factors. The photosensitization mechanism of orthogonal BODIPY dimers is demonstrated to be strongly related to their intrinsic intramolecular charge transfer (ICT) character through the spin-orbit charge-transfer intersystem crossing (SOCT-ISC) mechanism. Thus, singlet oxygen generation can be effectively modulated through the solvent polarity and the presence of electron-donating or withdrawing groups in one of the BODIPY units. The photodynamic therapy (PDT) activity is demonstrated by in vitro experiments, showing that selected photosensitizers are efficiently internalized into HeLa cells, exhibiting low dark toxicity and high phototoxicity, even at low PS concentration (0.05-5×10−6 m). [ABSTRACT FROM AUTHOR]

The Front Cover illustrates bright and stable deep‐red emission from a designed aza‐BODIPY chromophore. By careful selection of the substitution pattern of the fluorophore, the laser emission can be pushed towards the near‐infrared region of the spectrum. More information can be found in the Article by A. Prieto‐Castañeda et al. on page 75 in Issue 2, 2019 (DOI: 10.1002/cptc.201800225). [ABSTRACT FROM AUTHOR]