The Normalizing Constant in the BG/BB Model

Guiding the Design of Organic Photocatalyst for PET-RAFT Polymerization: Halogenated Xanthene Dyes

“…On the basis of the reduced oxygen inhibition period for EOB compared to EY, EOB should exhibit a higher Φ T compared to EY; however, the xanthene core of EOB is only disubstituted with Br, and the heavy atom effect is not as significant for EB compared to EY. Interestingly, from the ground state frontier orbitals (Figure 7E), we observed distinct intermolecular charge shift character upon excitation, evidenced by accumulation of electron density on the −NO 2 side of LUMO, which was also reported as charge transfer (CT) for EOB 105 (as it is not a typical donor−acceptor CT, 34 we prefer the term charge shift, which is used herein). This character is in principle due to the strongly electron-withdrawing −NO 2 groups distributed on a single side of the xanthene core, which results in a charge shift from Br to −NO 2 upon excitation (Figure 7E).…”

“…27,85−87 Similarly, the photophysical and electrochemical properties of organic PCs can be tuned by the introduction/modification of substituents on the aryl chromophore. 31,34,36,52,88 Correspondingly, changes to the halogen atoms on the xanthene aryl group lead to large differences in the photophysical and electrochemical properties of the PCs, i.e., Φ T and E 0 (PC •+ / 3 PC*) (Table 2). Despite these differences, the spectral profiles of these halogenated xanthene dyes are similar as shown by UV−vis spectroscopy of the PETRAFT polymerization mixtures (Figure 1C), while ε of the dyes at their λ max varies in the range 87000−98000 M −1 cm −1 (Table 1).…”

“…To guide the rational design and optimization of organic PCs that satisfy the specific needs of photo-RDRP and organic synthesis, researchers recently started to explore the relationships between PC structure and the performance of photocatalyzed systems. For example, structure−property relationships have been established for organic PCs that affect excited state redox potentials, 27 charge transfer characters, 27,34,35 and triplet quantum yields 36 based on dihydrophenazine and phenoxazine derivatives in organocatalyzed photo-ATRP (OATRP). Very recently, Kim, Gierschner, and Kwon also generated a library of donor−acceptor PCs and used a computer-aided strategy to elucidate the PC property− performance relationship in O-ATRP.…”

Photoinduced Organocatalyzed Atom Transfer Radical Polymerization Using Low ppm Catalyst Loading

“…15,16 More recently, organic photoredox catalysts 17 (PCs) based on perylene, 18 phenothiazine, 19 dihydrophenazine, 20 and phenoxazine 21 chromophore motifs have been developed to mediate organocatalyzed ATRP (O-ATRP) to produce polymers with controlled MW, high initiator efficiency (I* = MW theo /MW exp ), and low Đ ( Figure 1) while avoiding the possibility for incorporating metal contamination into the polymer product. 22,23 Since the seminal reports on O-ATRP, PC structural modifications, 24 photophysical characterizations, [25][26][27] solvent effects, 28 light intensity modulations, 29 and synthesis of higher-order polymer architectures [30][31][32] have been reported to advance the O-ATRP processes.…”