Two‐Photon Initiating Efficiency of a Ditopic Alkoxynitrostilbene Reacting through a Self‐Regenerative Mechanism

Abstract

The photophysical properties and the photoinitiating reactivity of a ditopic alkoxynitrostilbene were compared to those of its single branch chromophore used as a reference. Whereas a trivial additive effect is observed when considering the oneand two-photon absorption properties, a clear and very significant amplification has been highlighted for the photoreactivity of this free radical photoinitiator which was used as a hydrogen abstractor in presence of an aliphatic amine coreactant. We indeed demonstrate that the proximity of two nitroaromatics moieties within the same molecular architecture gives rise to an original cycling mechanism based on a stepwise photo triggering of each photoredox center followed by a subsequent regenerative process. The combination of a high two-photon absorption cross-section (δ 780nm � 330 GM) with a strong enhancement in photoreactivity makes this nitrostilbene bichromophore a very suitable candidate for two-photon polymerization applications.

The forgotten reagent of photoredox catalysis

“…[90][91][92] They are also prevalent sensitisers in photoinitiated polymerisation for microfabrication and 3D printing, 93 and offer exqui-site spatial control. 94 Examples of two photon absorbers in photoredox catalysis are rare, despite the fact that archetypal catalysts [Ru(bpy) 3 ] 2+ and Ir( ppy) 3 exhibit modest 2PA cross sections (7 GM [Goeppert-Mayer, 1 GM = 10 −50 cm 4 s per photon per molecule], 810 nm and 20 GM, 800 nm, respectively). 95,96 Tungsten(0) arylisocyanide complexes exhibit strong 2PA cross sections (∼1000 GM, 810 nm) and catalysed the reduction of aryl bromides using near infrared light (λ = 810 nm, ∼1.5 W m −2 Fig.…”

Photoactivable alizarin and eugenol-based materials for antibacterial applications

“…in coatings, microelectronics, adhesives, dental applications and more recently, 3D-photoprinting technology [1][2][3]. Also, photochemical reactions have been widely studied in other valuable fields of innovation such as the synthesis of biomaterials [4], (semi)interpenetrated networks [5], photoactivable materials [6][7][8][9], living/controlled polymerizations [10][11][12][13][14], two-photon polymerizations [6,[15][16][17], spatially controlled polymerizations [18], and so forth.…”

Comparative Photoinitiating Performances of Donor–Acceptor Multibranched Triphenylamines Designed for Light-Triggered Micropatterning Applications

“…and on the photophysical properties of the photoinitiators. These latter systems play a pivotal role in various photoinitiation strategies such as hydrogen abstraction reactions, , energy transfer, , or regenerative photoredox reactions. , The development of highly reactive photoinitiating systems is a very active research area . Various innovative objectives have motivated the design of new photoinitiators: (i) increasing the dye absorption ability to reduce the irradiation exposure time, (ii) shifting the irradiation wavelength toward the visible or near-infrared (NIR) region to increase the photon penetration depth into the photocurable resin, (iii) ensuring better biocompatibility and low cytotoxicity for biomedical applications, and (iv) implementing an added functionality into the final photopatterned materials such as bactericidal effects and postprinting ability .…”

“…and on the photophysical properties of the photoinitiators. These latter systems play a pivotal role in various photoinitiation strategies such as hydrogen abstraction reactions, 7,8 energy transfer, 9,10 or regenerative photoredox reactions. 11,12 The development of highly reactive photoinitiating systems is a very active research area.…”