Photoredox process induced polymerization reactions: Iridium complexes for panchromatic photoinitiating systems

Structural Effects in the Iridium Complex Series: Photoredox Catalysis and Photoinitiation of Polymerization Reactions under Visible Lights

“…Indeed, conventional Ir(III) complexes mainly absorb in the UV and the spectrum presents a rather weak visible tail that allows FRP and CP in the purple/blue range . Incorporation of carefully selected ligands has already led to improved properties: for example, the presence of a phenylisoquinoline ligand in iridium complexes extended the absorption up to 532 nm (e.g., Ir_9 or Ir_12 in Scheme ) and even 635 nm (e.g., Ir_7 and Ir_8 in Scheme ) . In the following, we prepare 14 novel derivatives ( Ir_1–Ir_6 , Ir_10 , Ir_11 , Ir_13–Ir_18) and explore the structural effects toward the initiation efficiency of the FRP of a triacrylate and the CP of a diepoxide under a halogen lamp or laser diodes at 457, 473, or 532 nm, in the presence of PISs consisting in an iridium complex (Scheme ) and one or more additive chosen among N ‐methyldiethanolamine (MDEA), 2‐bromoacetophenone (R‐Br), or diphenyliodonium hexafluorophosphate (Iod, Ph 2 I + ).…”

Recent Advances on Copper Complexes as Visible Light Photoinitiators and (Photo) Redox Initiators of Polymerization

“…Complexes could also be isolated by precipitation, facilitating the purification process. The way how to recover these complexes is totally different to that used for the previously mentioned iridium complexes that could only be synthesized in low yields, but also required an extensive purification process to be obtained in pure form [37][38][39][40][41][42]. As an interesting feature, the three complexes displayed a strong absorption in the near-visible range, with absorption maxima at 380 nm for Cu-1 and Cu-2, and 383 nm for Cu-3 (See Figure 3).…”

“…As a result of this, the photoinitiator content can be drastically reduced, addressing the toxicity issue. However, organic dyes are not the only ones capable to exhibit high molar extinction coefficients, and, in the literature, highly efficient photoinitiators of polymerization based on iridium complexes have notably been reported, outperforming benchmark photoinitiators such as phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide (BAPO) or camphorquinone (CQ) [37][38][39][40][41][42]. Their remarkable efficiencies were notably related to their long-living excited states, enabling the photosensitizers to react efficiently with the different additives introduced into the photocurable resins.…”

Recent Advances on Visible Light Metal-Based Photocatalysts for Polymerization under Low Light Intensity

“…In fact, iridium complexes have revolutionized the photocatalysis applied to photopolymerization by the possibility to involve these complexes in oxidative and reductive processes. Indeed, when introduced in a three-component Ir complex/iodonium salt/silane system, Ir complexes are engaged in an oxidative mechanism [56,57]. Conversely, in the three-component Ir complex/amine/alkyl halide system, Ir complexes are involved in a reductive pathway [23,[58][59][60][61].…”

“…Following these pioneering works on photopolymerization, thirty iridium complexes (Ir-1-Ir-30) were examined as photocatalysts for the FRP of acrylates, the CP of epoxides, the FRPCP of N-vinylcarbazole (NVK), or the generation of IPN. Their chemical structures are presented in Figure 5 [56][57][58][70][71][72].…”