Ion-Pair Complexes of Pyrylium and Tetraarylborate as New Host–Guest Dyes: Photoinduced Electron Transfer Promoting Radical Polymerization

Abstract

Ultrafast transient absorption spectroscopy, NOESY-NMR, and EPR spectroscopy shed light on how π−π stacking interactions combined with electrostatic interactions can be used to form stable ion-pair complexes between pyrylium and tetraarylborate ions in which the interaction of the π-delocalized clouds promotes the observation of new radiative processes and also electron transfer processes excitation using visible light. The results exhibit a striking combination of properties, chemical stability and photophysical and photochemical events, that make these ion-pair complexes as a step toward the realization of chromophore/luminescent materials and also their use as a new monophotoinitiator system in radical polymerization reactions.

Inverse photochromism in viologen–tetraarylborate ion-pair complexes: optical write/microwave erase switching in polymer matrices

“…The Gibbs free energy change for the electron transfer reaction from the singlet excited state of these complexes is expected to be around -0.9 eV. 7,20 A partially charge separated state (PCS) is commonly observed in CT complexes. 2,11,22 For a fully charge transferred state (FCS), one-electron transfer accompanied by a change in valence leads to structures classified as radical pairs (RPs, bottom right of Scheme 1).…”

Novel phenylamine‐based oxime ester photoinitiators for LED‐induced free radical, cationic, and hybrid polymerization

“…A very wide of multicomponent photoinitiator (PI) systems has been reported, for example, using several compounds such as pyrylium derivatives, metal complexes, camphorquinone or oxometalates. [15][16][17][18][19] The development of Type I PI has the advantage to reduce the complexity of the PIS (monocomponent system). In this context, it is evident that direct homolytic cleavage induced by LED light is a more straightforward mechanism to generate the initiating species.…”

“…A very wide of multicomponent photoinitiator (PI) systems has been reported, for example, using several compounds such as pyrylium derivatives, metal complexes, camphorquinone or oxometalates 15–19 . The development of Type I PI has the advantage to reduce the complexity of the PIS (monocomponent system).…”

Wavelength-Dependent, Large-Amplitude Photoinitiating Reactivity within a Carbazole-Coumarin Fused Oxime Esters Series

“…Indeed, this approach consists in combining a LED light-sensitive chromophore playing the pivotal role of photoredox center, − hydrogen abstractor, − or energy donor , with other co-initiators that will be involved in the multiple reaction sequences for free radical production. A very wide variety of multicomponent systems has been reported using, for instance, camphorquinone, metal complexes, pyrylium derivatives, or polyoxometalates . However, one of the detrimental effects of this approach is obviously the occurrence of multiple reaction steps that tend to lengthen the overall time scale of the photoinitiation.…”