- The synthesis of dendroflorin
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The first synthesis of dendroflorin has been achieved in 10 steps with an overall yield of 5.5%. The key step in the synthesis features the biphenyl structure is built through Suzuki–Miyaura reaction. In addition, the ortho-localization effect induced by aromatic substituent during the bromination of intermediate 8 is also observed and discussed.
- Deng, Yi,Jiang, Kun,Cai, Mao-Jun,Qu, Shi-Jin,Dai, Yi-Ru,Tan, Chang-Heng
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Read Online
- Off the back or on the side: Comparison of meso and 2-substituted donor-acceptor difluoroborondipyrromethene (bodipy) dyads
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The preparation of several difluoroborondipyrromethene (Bodipy) dyads is described Incorporating covalently attached hydroqumone/qumone groups at the 2-position (BDSHQ, BD-SQ, BD-SPHQ, BD-SPQ). The compounds, currently under investigation as chemical sensors for reactive oxygen species, show various levels of fluorescence depending on the oxidation state of the appended group. The 19F NMR spectrum for BD-SHQ in CDCl3 at room temperature reveals the two fluorines are inequivalent on the NMR timescale. In contrast, the 19F NMR spectrum for the counterpart quinone compound, BD-SQ, is consistent with two equivalent: fluorine atoms. The two results are interpreted as the quinone is free to rotate around the connector bond, whereas this motion is restricted for the hydroquinone group and makes the fluorines chemically inequivalent. Cyclic voltammograms recorded for all derivatives in CH2Cl2 electrolyte solution are consistent: with typical Bodipy-based redox chemistry; the potentials of which depend on factors such as presence of the phenylene spacer and oxidation state of the appended group. A comparison of the electrochemical behaviour with the counterpart meso derivatives reveals some interesting trends which are associated with the location of the HOMO/LUMOs. The absorption profiles for the compounds in CH 3CN are again consistent with Bodipy-based derivatives, though there are some subtle differences in the band-shapes of the closely-coupled systems. In particular, the absorption spectra for the dyad, BD-SQ, in a wide range of solvents are appreciably broader than for BD-SHQ. Femtosecond transient absorption spectroscopy performed on the hydroquinone derivatives, BD-SHQ and its meso analogue is interpreted as electron transfer occurs from, the hydroquinone unit to the first-excited singlet (S1) state of the Bodipy center, followed by ultrafast charge recombination to reinstate the ground state. The coupling of OH vibrations to the return electron transfer process is invoked to explain the lack of clear identification of the charge-separated state in the transient records.
- Benniston, Andrew C.,Copley, Graeme,Lenimetyinen, Helge,Tkachenko, Nikolai V.
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experimental part
p. 2867 - 2877
(2010/08/05)
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- Redox-controlled fluorescence modulation in a BODIPY-quinone dyad
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The synthesis and properties of two closely related boron dipyrromethene (BODIPY) derived dyads, incorporating redoxactive quinone units appended at the meso position, are described. For one dyad, the quinone unit is attached directly to the BODIPY core, whereas a phenylene spacer separates the two units in the second compound. Each of the quinone units is readily converted, by both chemical and electrochemical means, to the corresponding hydroquinone derivative. The strong fluorescence normally associated with the BODIPY unit is efficiently quenched in both dyads in their quinone forms. This is attributed to deactivation of the first excited singlet state by a way of an intramolecular electron-transfer process. By comparison, moderately intense fluorescence is observed for the hydroquinone derivative containing the phenylene spacer, but not for the analogous directly coupled dyad. The potential sensing capabilities of the phenylene-spaced BODIPY quinone and hydroquinone dyads, towards reducing and oxidising species such as ascorbate and peroxide, were tested in a biomembrane mimic. A reversible modulation in fluorescence could be readily detected by eye under standard UV-light excitation. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Benniston, Andrew C.,Copley, Graeme,Elliott, Kristopher J.,Harrington, Ross W.,Clegg, William
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experimental part
p. 2705 - 2713
(2009/04/07)
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