Selective Modification for Red‐Shifted Excitability: A Small Change in Structure, a Huge Change in Photochemistry

Abstract

We developed three bathochromic, green‐light activatable, photolabile protecting groups based on a nitrodibenzofuran (NDBF) core with D‐π‐A push–pull structures. Variation of donor substituents (D) at the favored ring position enabled us to observe their impact on the photolysis quantum yields. Comparing our new azetidinyl‐NDBF (Az‐NDBF) photolabile protecting group with our earlier published DMA‐NDBF, we obtained insight into its excitation‐specific photochemistry. While the “two‐photon‐only” cage DMA‐NDBF was inert against one‐photon excitation (1PE) in the visible spectral range, we were able to efficiently release glutamic acid from azetidinyl‐NDBF with irradiation at 420 and 530 nm. Thus, a minimal change (a cyclization adding only one carbon atom) resulted in a drastically changed photochemical behavior, which enables photolysis in the green part of the spectrum.

Inactivation of Competitive Decay Channels Leads to Enhanced Coumarin Photochemistry

“…[8,9] Taking the coumarin photocage as an example, popular methods were the extension of the π-system, or the addition of donor and acceptor substituents (see Figure 1a). [10][11][12][13] Also with other photolabile protecting groups, for example BODIPY, [14,15] fluorenol, [16,17] or nitrobenzyl [18,19] a considerable red-shift was achieved with similar approaches. Nevertheless, the improvement of the second parameter, the uncaging efficiency, has not Structures and photophysical properties of DEACM 1 and ATTO 390.…”

Tris(4′-Nitrobiphenyl)amine─An Octupolar Chromophore with High Two-Photon Absorption Cross-Section and Its Application for Uncaging of Calcium Ions in the Near-Infrared Region

“…The product was purified by silica gel column chromatography (hexane/EtOAc = 95:5) to give desired compound 2 (51.1 mg, 80%) as a red solid. (5). In a round-bottom flask, compound 7 50 (114.4 mg, 0.17 mmol), compound 8c (125.9 mg, 0.21 mmol), Pd(PPh 3 ) 4 (22.1 mg, 0.019 mmol), and K 3 PO 4 (120.2 mg, 0.57 mmol) were mixed in 1,4-dioxane/H 2 O (2:1, 1.5 mL).…”

Rethinking Uncaging: A New Antiaromatic Photocage Driven by a Gain of Resonance Energy

“…Deeper insight into these processes can be gained with computational methods, spectroscopically, with systematic synthetic work – or ideally with all of these approaches working together. The change of one parameter for example the solubility can have an impact on the excited state reactivity and therefore change the entire photochemistry [6–9] . Hence, the design of new photoactivatable compounds needs to be based on elementary, but relevant concepts, as for example nitro‐push–pull‐systems or Zimmerman's meta ‐effect (Figure 1a,b) [10–12] .…”

“…The change of one parameter for example the solubility can have an impact on the excited state reactivity and therefore change the entire photochemistry. [ 6 , 7 , 8 , 9 ] Hence, the design of new photoactivatable compounds needs to be based on elementary, but relevant concepts, as for example nitro‐push–pull‐systems or Zimmerman's meta ‐effect (Figure 1 a,b). [ 10 , 11 , 12 ] In the last decades, numerous new photocleavable protecting groups (PPGs, photocages) evolved from these existing concepts in photochemistry.…”