Triarylisocyanurate‐Based Fluorescent Two‐Photon Absorbers

Abstract

The synthesis and characterization of six triarylisocyanurates, featuring 2,7‐fluorenyl or 9,10‐anthracenyl groups incorporated in their peripheral arms are reported. Photophysical studies reveal that these new octupolar derivatives are more fluorescent (ΦF≥0.60 for all new compounds except for 1,3,5‐tri(9H‐fluoren‐2‐yl)‐1,3,5‐triazinane‐2,4,6‐trione 3) and present a red‐shifted lowest absorption and emission compared to their known phenyl analogues of comparable size. Depending on the nature of the terminal substituent, fast intramolecular energy transfer among the three arms or localization of the excitation on a single branch occurs after population of their first singlet excited state. The latter effect was only observed in the presence of strongly electron‐releasing substituents in polar media. These new chromophores are also better two‐photon absorbers than the 1,4‐phenylene‐based isocyanurates reported so far, with cross sections σ2≥500 GM at 770 nm for 4‐NPh2 the fluorenyl group containing (13) and the anthracenyl group containing (14) chromophores. All these spectroscopic features, analyzed with the help of quantum chemical calculations, are crucial for the design of new biphotonic fluorescent dyes.

Two-photon absorption and two-photon-induced isomerization of azobenzene compounds

“…One may mention that there are several additional strategies to even further enlarge the TPA cross-sections of the chromophores, 61 including the multibranched design of the molecules, [62][63][64] which leads to the larger number of the active, multiphoton absorbing centres with the possibility of their mutual interactions, metallation of the structures as well as aggregation induced enhancements.…”

1,3,5-Triaryl-1,3,5-Triazinane-2,4,6-Trithiones: Synthesis, Electronic Structure and Linear Optical Properties

“…After tedious chromatographic separation, the desired product 5 was eventually isolated in poor yield (11%) and was characterized (Table 1). To access the extended thioisocyanurate derivative 5, a Sonogashira coupling reaction [28] between the previously isolated tris(4-iodophenyl)thioisocyanurate precursor 4-I and the known alkyne 8 [29] was performed (Scheme 4), analogous to that with related isocyanurates [4]. After tedious chromatographic separation, the desired product 5 was eventually isolated in poor yield (11%) and was characterized (Table 1).…”

“…These results were from the presence of sulfur and oxygen atoms at the periphery of the central heterocyclic core and, as expected, they aligned with the C=X bond (X = O, S), which is distinct from the two others ( Figures S15 and S16 and Table S5). For the extended derivative 5 , as for its isocyanurate analogue 3 [4], essentially two types of nearly isoenergetic conformations coexist for the GS at ambient temperatures; a statistically favored one (C1) with only two arms oriented "on the same side" of the central heterocycle and a low dipole moment (Table 3) and a second one with three arms "on the same side" (C2) and with a larger dipole moment perpendicular to the central ring (2.31 D). The stepwise replacement of oxygen by sulfur along the series 1-Me, 6-Me, 7-Me, and 4-Me allowed us to probe the impact of this compositional change on the electronic structure of these compounds ( Figure 5).…”

“…π-Extended derivatives such as 2-X were shown to possess good two-photon absorption (2PA) cross-sections and were often highly fluorescent; this is particularly the case for derivatives featuring strongly electron-rich terminal substituents X [3]. More recently, related triarylisocyanurates such as 3 were also examined for their 2PA cross-section/fluorescence products [4], in the context of using these functionalized analogues as two-photon dyes for fluorescent bio-imaging purposes [5]. As the introduction of more polarizable sulfur atoms has often been demonstrated to boost the third-order NLO properties, [6][7][8] we wondered if a similar behavior would be seen in proceeding to the 1,3,5-triazinane-2,4,6-trithione (thioisocyanurate) analogues of 1-X and, in particular, to the model compound 5, the thioisocyanurate analogue of 3.…”

“…d nc: not computed. e Calculated for a computationally-simpler model complex of 3 at the MPW1PW1/6-31G* level in CH 2 Cl 2[4].…”