Redox‐Controlled Fluorescence Modulation in a BODIPY‐Quinone Dyad

Benniston, Andrew C.; Copley, Graeme; Elliott, Kristopher J.; Harrington, Ross W.; Clegg, William

doi:10.1002/ejoc.200800191

Cited by 89 publications

(71 citation statements)

References 60 publications

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“…This process can be ascribed to formation of the Bodipy p-radical cation. [35,36] The second peak seen under these conditions is due to oxidation of the C 60 unit (possibly the tertiary amine of the pyrrolidine), and is electrochemically irreversible, with the anodic peak potential being 1.40 V vs. SCE. [37] A series of peaks are seen on reductive scans, but these are easily assigned by comparison with the cyclic voltammogram recorded for the equimolar mixture (Figure 1).…”

Section: Resultsmentioning

confidence: 98%

Selective Triplet‐State Formation during Charge Recombination in a Fullerene/Bodipy Molecular Dyad (Bodipy=Borondipyrromethene)

Ziessel

Allen

Rewinska

et al. 2009

Chemistry A European J

198

299

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A conformationally restricted molecular dyad has been synthesized and subjected to detailed photophysical examination. The dyad comprises a borondipyrromethene (Bodipy) dye covalently linked to a buckminsterfullerene C60 residue, and is equipped with hexadecyne units at the boron centre in order to assist solubility. The linkage consists of a diphenyltolane, attached at the meso position of the Bodipy core and through an N-methylpyrrolidine ring at the C60 surface. Triplet states localised on the two terminals are essentially isoenergetic. Cyclic voltammetry indicates that light-induced electron transfer from Bodipy to C60 is thermodynamically favourable and could compete with intramolecular energy transfer in the same direction. The driving force for light-induced electron abstraction from Bodipy by the singlet excited state of C60 depends critically on the solvent polarity. Thus, in non-polar solvents, light-induced electron transfer is thermodynamically uphill, but fast excitation energy transfer occurs from Bodipy to C60 and is followed by intersystem crossing and subsequent equilibration of the two triplet excited states. Moving to a polar solvent switches on light-induced electron transfer. Now, in benzonitrile, the charge-transfer state (CTS) is positioned slightly below the triplet levels, such that charge recombination restores the ground state. However, in CH2Cl2 or methyltetrahydrofuran, the CTS is slightly higher in energy than the triplet levels, and decays, in part, to form the triplet state localized on the C60 residue. This step is highly specific and does not result in direct formation of the triplet excited state localized on the Bodipy unit. Subsequent equilibration of the two triplets takes place on a relatively slow timescale.

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Section: Resultsmentioning

confidence: 98%

Selective Triplet‐State Formation during Charge Recombination in a Fullerene/Bodipy Molecular Dyad (Bodipy=Borondipyrromethene)

Ziessel

Allen

Rewinska

et al. 2009

Chemistry A European J

198

299

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“…[2,4] Indeed, instead of an on-off two-state system, it should be possible to prepare dyads that display off-to-on fluorescent switching upon redox activation. Such dyads should present complementary properties to 3-chloro-6-methoxytetrazine.…”

Section: Introductionmentioning

confidence: 99%

Design of New Tetrazine–Triphenylamine Bichromophores – Fluorescent Switching by Chemical Oxidation

et al. 2012

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Original new fluorescent and electroactive compounds have been prepared, which feature two different fluorescent groups linked through an oxygen atom spacer. We describe here the synthesis, photophysical and electrochemical properties and their interplay, and our theoretical calculations. These molecules are composed of two fluorophores, an electron‐rich triphenylamine unit and an electron‐poor tetrazine unit. Although the bichromophores are not fluorescent in the neutral state due to a photoinduced electron transfer from the triphenylamine unit to the tetrazine unit, one can restore the fluorescence by oxydation of the triphenylamine moiety. Thus, a redox‐fluorescent switch has been realized.

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“…After passing the mixture through a silica pad, eluting first with n-hexane and then with dichloromethane, an orange solid was obtained (0.051 g, 82 %). [12] Received: November 29, 2011 Revised: January 10, 2012 Published online: March 19, 2012 (5). [12] …”

Section: Methodsmentioning

confidence: 99%

“…The fluorescent aryl bromide derivative of Bodipy, 1, was synthesized in a one-pot reaction. [5] Following difficulties with retaining the two fluorine atoms in the later reduction step, [6] we treated 1 with two equivalents of phenyllithium to give the novel derivative 2 a, which was characterized by X-ray crystallography ( Figure S1 in the Supporting Information). A palladium-catalyzed coupling reaction of 2 a with diethylphosphite yielded the fluorescent phosphonate 3 a, which was also analyzed by X-ray crystallography ( Figure S3 in the Supporting Information).…”

mentioning

confidence: 99%

Air‐Stable, Highly Fluorescent Primary Phosphanes

et al. 2012

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Primary phosphanes (RPH 2 ) have a reputation as noxious compounds which are spontaneously flammable in air. [1] We have recently demonstrated, however, that they can be stabilized to air oxidation without any need for steric protection, providing sufficient p conjugation is incorporated into the organic R group; thus we were able to prepare the first air-stable chiral primary phosphanes. [2] Since then, we have been developing a working model based on DFT, which indicates that, contrary to popular belief, many primary phosphanes will be air-stable if the molecule contains a high degree of conjugation (see below). [3] As such, the model predicted that the incorporation of the phosphino group onto a boron dipyrromethene (Bodipy [4] ) skeleton would also produce air-stable primary phosphanes. These phosphanes should provide a highly versatile gateway into a vast range of fluorescent phosphane derivatives, which are currently sorely underrepresented, despite the importance of phosphanes in catalytic and biomedical applications. To explore this exciting possibility, we commenced a synthetic study based on the strategy shown in Scheme 1. The fluorescent aryl bromide derivative of Bodipy, 1, was synthesized in a one-pot reaction. [5] Following difficulties with retaining the two fluorine atoms in the later reduction step, [6] we treated 1 with two equivalents of phenyllithium to give the novel derivative 2 a, which was characterized by X-ray crystallography ( Figure S1 in the Supporting Information). A palladium-catalyzed coupling reaction of 2 a with diethylphosphite yielded the fluorescent phosphonate 3 a, which was also analyzed by X-ray crystallography ( Figure S3 in the Supporting Information). Phosphonate 3 a was then reduced quantitatively to the primary phosphane 4 a by using a combination of lithium aluminum hydride and chlorotrimethylsilane. As predicted by the model, 4 a was found to be stable to oxidation; when exposed to air both in the solid state and in chloroform solution over seven days, no decomposition was observed. Importantly, incorporation of the phosphonate and the phosphino group did not dramatically alter the photophysical properties of the molecules when compared to the parent aryl bromide 2 a (Table 1). This finding was not unexpected, as the results from our DFT calculations show that the highest occupied molecular orbitals (HOMOs), up to the HOMO-6 of 2 a, do not incorporate the phosphorus atom, although they are affected by the phenyl rings on the boron atom ( Figure S6 in the Supporting Information). It is noteworthy that, after the aryl substitution of 1, the quantum yield (F) of aryl bromide 2 a drops from 0.65 to 0.079. In an effort to maintain the high quantum yield of 1, but to still allow the reduction step, we treated 1 with two equivalents of methyllithium to give the dimethyl aryl bromide derivative 2 b, which was also characterized by X-ray crystallography ( Figure S2 in the Supporting Information). Substitution of the fluorine atoms by methyl groups has a less detrimental effe...

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Redox‐Controlled Fluorescence Modulation in a BODIPY‐Quinone Dyad

Cited by 89 publications

References 60 publications

Selective Triplet‐State Formation during Charge Recombination in a Fullerene/Bodipy Molecular Dyad (Bodipy=Borondipyrromethene)

Selective Triplet‐State Formation during Charge Recombination in a Fullerene/Bodipy Molecular Dyad (Bodipy=Borondipyrromethene)

Design of New Tetrazine–Triphenylamine Bichromophores – Fluorescent Switching by Chemical Oxidation

Air‐Stable, Highly Fluorescent Primary Phosphanes

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