Design, Synthesis, and Reaction of π-Extended Coumarin-based New Caged Compounds with Two-photon Absorption Character in the Near-IR Region

Abstract

Novel π-extended coumarin-based chromophores were designed with two-photon absorption (TPA) character in the near-IR region. Caged benzoates with a TP-responsive chromophore were synthesized, and their TP-uncaging reactions were conducted under near-IR light. The 6,7-dimethoxy-substituted derivative had a high TPA cross-section of 69 GM at 740 nm. The 7-methoxysubstituted derivative showed a high TPA uncaging efficiency with a TPA efficiency of 3.4 GM at 710 nm.Keywords: Caged compounds | Two-photon absorption | Donor-π-AcceptorCaged compounds, 1 the inactive forms of bioactive molecules formed using a photolabile protecting group (PPG), 2 are now used to elucidate the mechanism of bioactivity of substances in various life processes and phenomena. For instance, caged compounds contribute to the development of new medicines. The PPG is removed photochemically under neutral conditions without chemical reagents, thus rapidly releasing the bioactive compound. This efficient uncaging is biologically useful because the timing, location, and amplitude of photoirradiation can be controlled. Thus, the photoinduced release of bioactive molecules has been utilized in various fields such as neuroscience, cell patterning, or biomedical science. 35 Coumarin derivatives have been used to study various functions of biomolecules and for cellular imaging.6 The advantages of coumarin as a chromophore include its inherent fast response to photolysis, thermal stability, high molar extinction coefficient, and good fluorescent property for monitoring its reactions in vivo.7 However, the recent concern for physiological application of coumarin-based compounds is mainly its short absorption wavelength. Coumarin itself possesses an absorption wavelength maximum of 274 nm in methanol.8 Due to this short wavelength, cell damages cannot be avoided using one-photon absorption (OPA).9 But better penetration to the deeper part of cells 10 can be afforded using chromophores having significant twophoton absorption (TPA) character in the near-IR region. 11,12Chromophores with TPA character have attracted much attention because of their application in physiology. Caged compounds with TPA character enable greater spatial control of the release of bioactive substances. 13 For practical applications, a higher uncaging efficiency is necessary to conduct biological studies. The uncaging efficiency for OP excitation is defined as the uncaging quantum yield (Φ u ) multiplied by the excitation probability (¾: molar extinction coefficient). Similarly, the efficiency ¤ u of a TP excitation process is expressed using the TPA cross-section (· 2 ): ¤ u = Φ u · 2 . The minimum threshold value of TP efficiency for in vivo studies was reported as 3 GM.14 In 1999, Furuta et al. In this study, a coumarin containing a stilbene skeleton (12 GM at 514 nm) 18 with a p-nitrophenyl group as the electronwithdrawing group was designed to increase the TPA crosssections due to its dipolar character (Figure 1). 19 The cyclic structure should prevent cistrans isomerization ...

Replacing Two Chlorido Ligands by a Bipyridine Ligand in Ruthenium Nitrosyl Complexes with NO‐Release Capabilities: A Comparative Study

“…To clarify this point, we compared the fluorene moiety to other organic fragments and found that its donating capabilities are between those of p ‐dimethylaminophenyl and p ‐methoxyphenyl; thus, we can assume that it behaves as an efficient electron donor (see Supporting Information). Therefore, we have applied the two‐level model to estimate the σ TPA values of the ruthenium derivatives on the basis of the electronic parameters available in Gaussian09 …”

“…Therefore, we have applied the two-level model to estimate the σ TPA values of the ruthenium derivatives on the basis of the electronic parameters available in Gaussian09. [40] Z-Scan Measurements: The Z-scan technique [23] was used to measure the nonlinear absorption coefficients of the samples at λ = 800 nm through the application of short laser pulses of 90 fs at a repetition rate of 1 kHz. The molecules under study were dissolved in acetonitrile at a concentration of 1 × 10 -2 mol L -1 .…”

Design and Synthesis of a Caged Carboxylic Acid with a Donor−π–Donor Coumarin Structure: One-photon and Two-photon Uncaging Reactions Using Visible and Near-Infrared Lights

“…The computational details are provided in Supporting Information. The predicted first absorption maximum of 7-dimethylamino-substituted coumarin (S 0 è S 1 transition) is slightly blue-shifted compared to its D-π-A analogue 1a (Figure S19) 22 . As expected for a D-π-D chromophores, a large TPA cross-section (of ca.…”

“…28 Donor (D)-acceptor (A) π-conjugated 29 coumarin derivatives 1 ( Figure 1) showed TP-induced uncaging in the NIR region, in which an electronwithdrawing group was introduced at the C3 position. 22 However, low quantum yields of 0.09 and 0.03 were observed for the uncaging reactions of 1a and 1b, respectively, decreasing the efficiency of the TP-induced uncaging reactions. This paper describes the synthesis and reactivity of a novel D-π-D conjugated coumarin-based caged compound 2 ( Figure 1), in which the D-substitution at the C3 position was achieved for the first time.…”

Dual-wavelength efficient two-photon photorelease of glycine by π-extended dipolar coumarins

“…The coumarin heterocyclic backbone, recognized as an efficient caging group,9,24–26 can undergo a wide panel of chemical functionalization modulating its optical properties. Introducing an electron-withdrawing group (EWG) at the 3-position of the coumarin cage21,27,28 was shown an influential way to red-shift both 1P and 2PA maxima respectively to the visible and the NIR,27,29–31 as evidenced by DEAC450 (Fig. 1).…”