Fluorescence Enhancement of a Porphyrin–Viologen Dyad by Pseudorotaxane Formation with Cucurbit[7]uril

Fathalla, Maher; Strutt, Nathan L.; Barnes, Jonathan C.; Stern, Charlotte L.; Ke, Chenfeng

doi:10.1002/ejoc.201402018

Cited by 16 publications

(12 citation statements)

References 80 publications

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“…32 Although researchers have previously investigated dicationic viologens for binding to CB[7], 33 and such viologens have been utilized as quenchers for fluorophores including napthalimides, 34 the fluorescence increase upon encapsulation with CB[7] to dicationic viologens is minor. 35, 36 In contrast, we found ( vide infra ) that the use of a mono-cationic bipyridine (bpy) that maintains reasonably strong CB[7] binding ( K a of approximately 10 6 M −1 ) 37 provides for much greater enhancement of fluorescence. The connection of these motifs via a short, flexible O(CH 2 ) 2 linker ensured spatial proximity, while functionalization at the imide position (on the opposite side of the molecule) with an alkyne unit allowed a reactive handle for facile surface modification (NMI 2 ) with the commercially available biotin-azide.…”

mentioning

confidence: 99%

A naphthalimide derived fluorescent sensor for solid-phase screening of cucurbit[7]uril–guest interactions

et al. 2016

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mentioning

confidence: 99%

A naphthalimide derived fluorescent sensor for solid-phase screening of cucurbit[7]uril–guest interactions

et al. 2016

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“…31,41,42 Thus, steady-state emission measurements were carried out below the saturation concentrations Page 4 of 9 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 (Fig. S7).…”

Section: Fluorescence Enhancement Of Ppyv On Threading Of Cb[n]mentioning

confidence: 99%

Threading the Needle: Fluorescent Poly-pseudo-rotaxanes for Size-Exclusion Sensing

et al. 2016

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Alternatively the portal of CB[8] appears to be large enough such that it doesn't have sufficiently large dipole-dipole interactions with the PPyV chain to promote a strong threading equilibrium. However we find that the portal of CB [7] is optimal for the threading of PPyV. The PPyV-CB[n] system was further exploited to demonstrate a dual-action sensor platform, combining the PL-responsive behavior demonstrated by PPyV towards electron-rich analytes with the size-exclusion properties imparted by volume of the respective CB[n] cavities. Thin films of PPyV-CB [7] were found to display reversible photoluminescence quenching when exposed to vapors of the biologically relevant molecule indole which is recovered under ambient conditions, suggesting prospects for new size-exclusion based selective sensory schemes for volatile electron-rich analytes.

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“…[15][16][17][18] With respect to the molecular axles employed to devise CB-based rotaxanes and pseudorotaxanes, those containing viologen recognition units are by far the most frequently used because of the high stability constants of CB : viologen complexes and the redox switching properties of these molecules. [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] The photochemical reduction of viologen units has also been explored in the presence of cucurbiturils to devise photoswitchable supramolecular assemblies. [35][36][37] In this work a molecular axle containing viologen and avylium units was synthesized and the formation of a pseudorotaxane with CB7 investigated (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal control over the co-conformational switching in pH-responsive flavylium-based multistate pseudorotaxanes

et al. 2015

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A multistate molecular dyad containing flavylium and viologen units was synthesized and the pH dependent thermodynamics of the network completely characterized by a variety of spectroscopic techniques such as NMR, UV-vis and stopped-flow. The flavylium cation is only stable at acidic pH values. Above pH ≈ 5 the hydration of the flavylium leads to the formation of the hemiketal followed by ring-opening tautomerization to give the cis-chalcone. Finally, this last species isomerizes to give the trans-chalcone. For the present system only the flavylium cation and the trans-chalcone species could be detected as being thermodynamically stable. The hemiketal and the cis-chalcone are kinetic intermediates with negligible concentrations at the equilibrium. All stable species of the network were found to form 1 : 1 and 2 : 1 host : guest complexes with cucurbit[7]uril (CB7) with association constants in the ranges 10(5)-10(8) M(-1) and 10(3)-10(4) M(-1), respectively. The 1 : 1 complexes were particularly interesting to devise pH responsive bistable pseudorotaxanes: at basic pH values (≈12) the flavylium cation interconverts into the deprotonated trans-chalcone in a few minutes and under these conditions the CB7 wheel was found to be located around the viologen unit. A decrease in pH to values around 1 regenerates the flavylium cation in seconds and the macrocycle is translocated to the middle of the axle. On the other hand, if the pH is decreased to 6, the deprotonated trans-chalcone is neutralized to give a metastable species that evolves to the thermodynamically stable flavylium cation in ca. 20 hours. By taking advantage of the pH-dependent kinetics of the trans-chalcone/flavylium interconversion, spatiotemporal control of the molecular organization in pseudorotaxane systems can be achieved.

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Fluorescence Enhancement of a Porphyrin–Viologen Dyad by Pseudorotaxane Formation with Cucurbit[7]uril

Cited by 16 publications

References 80 publications

A naphthalimide derived fluorescent sensor for solid-phase screening of cucurbit[7]uril–guest interactions

A naphthalimide derived fluorescent sensor for solid-phase screening of cucurbit[7]uril–guest interactions

Threading the Needle: Fluorescent Poly-pseudo-rotaxanes for Size-Exclusion Sensing

Spatiotemporal control over the co-conformational switching in pH-responsive flavylium-based multistate pseudorotaxanes

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