Enhancement of the Two-Photon Initiating Efficiency of a Thioxanthone Derivative through a Chevron-Shaped Architecture

Abstract

We investigated the one-and two-photon excitation properties of a new hybrid anthraceneÀthioxanthone (ANTX) system, which was assembled into a chevron-shaped molecular architecture. Such a geometrical association first preserves the high efficiency of the free radical photoinitiator and leads, in the same time, to a strong increase in the two-photon absorption (2PA) cross section by more than a factor of 30 as compared to thioxanthone (TX). A four-state model was required to fit the 2PA spectrum of ANTX, which clearly undergoes a strong enhancement in the low-frequency region. As a consequence, ANTX constitutes a suitable two-photon initiating chromophore with a much higher efficiency as TX used as reference. At λ exc = 710 nm for instance, we showed that the two-photon polymerization threshold of ANTX is five times lower with respect to that of TX. Additionally, we demonstrated by the fabrication of three-dimensional microstructures that this new hybrid system remains two-photon activable when excited at wavelengths near its one-photon absorption region as suggested by the sumÀoverstates model. We also show that this new twophoton initiator exhibits a higher reactivity than a diaminofluorene derivative, which is commonly used in two-photon polymerization.

Photoinitiators for two-photon polymerisation: effect of branching and viscosity on polymerisation thresholds

“…13,14 Carbonyl groups play a dual-role, as (1) strong electron acceptors and (2) efficient spin-orbit coupling agents to promote intersystem crossing. [15][16][17] A number of research groups have utilised carbonyl moieties in the creation of 2PA PIs, with high sensitivity and low polymerisation thresholds. 2,3,11,[17][18][19][20][21] These are oen focussed on several well-known functional components, including; a-b-unsaturated ketones, 3,16,21 thioxanthones, 1,15 ketocoumarins, 19,22 1,3-diketones 23 and acylo-phosphine oxides.…”

Theoretical evidence of metal-induced structural distortions in a series of bipyrimidine-based ligands

“…8 In the previous decade, quadratic Non Linear Optical (NLO) properties of octupolar tetrahedral D 2d and octahedral late metal complexes (D 3 ) with large π-donor backbones have been investigated. 4,9,10 The idea of using bipyrimidine ligands arose for different reasons: (i) strong π-delocalization, (ii) non planarity between two bipyrimidine moieties promoted by lone pair's interactions between the nitrogen atoms of the two pyrimidine fragments, which gives access to a pseudotetrahedral octupolar symmetry and (iii) strong ability to chelate a metal and possibly give a supra-molecular assembly. [11][12][13][14][15][16][17][18] Recently, a new class of three-dimensional NLO-phores of D 2d symmetry based on donor-substituted styryl bipyrimidine cores has been investigated.…”

Two-photon lithography in visible and NIR ranges using multibranched-based sensitizers for efficient acid generation

“…Multiphoton excitation constitutes an emergent technology with a rapid development due to the promising applications in a very wide range of domains including three-dimensional fluorescence imaging 1 , photodynamic therapy 2 , high density optical data storage 3 or two-photon fabrications [4][5][6][7][8][9][10][11] . By tightly focusing an excitation beam and taking advantage of the very low probability for the two-photon absorption (2PA) event, a spatial confinement of all primary and subsequent photoinduced processes are promoted.…”