A Cucurbit[7]uril Based Molecular Shuttle Encoded by Visible Room‐Temperature Phosphorescence

Gong, Yifu; Chen, Hui; Ma, Xiang; Tian, He

doi:10.1002/cphc.201500901

Cited by 82 publications

(56 citation statements)

References 62 publications

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“…The solubility of bTbk in water was around 50 µM, and CB [8] did not increase it very largely. However, these investigations allowed finding that molecular shuttles using cucurbiturils were not limited to CB [6] [48] or CB [7] [49][50][51] and that CB [8] could also behave as a functional ring in water-soluble molecular shuttles provided the guest had the right structure.…”

Section: Discussionmentioning

confidence: 99%

EPR Spectroscopy: A Powerful Tool to Analyze Supramolecular Host•Guest Complexes of Stable Radicals with Cucurbiturils

et al. 2020

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Stable organic free radicals are increasingly studied compounds due to the multiple and unusual properties imparted by the single electron(s). However, being paramagnetic, classical methods such as NMR spectroscopy can hardly be used due to relaxation and line broadening effects. EPR spectroscopy is thus better suited to get information about the immediate surroundings of the single electrons. EPR has enabled obtaining useful data in the context of host•guest chemistry, and a classical example is reported here for the stable (2,2,6,6-tetramethyl-4-oxo-piperidin-1-yl)oxyl or 4-oxo-TEMPO nitroxide (TEMPONE) inside the macrocycle host cucurbit [7]uril (CB[7]). Generally and also observed here, a contraction of the spectrum is observed as a result of the reduced nitrogen coupling constant due to inclusion complexation in the hydrophobic cavity of the host. Simulations of EPR spectra allowed determining the corresponding binding constant pointing to a weaker affinity for CB [7], compared to TEMPO with CB [7]. We complement this work by the results of EPR spectroscopy of a biradical: bis-TEMPO-bis-ketal (bTbk) with cucurbit[8]uril (CB[8]). Initial investigations pointed to very weak effects on the spectrum of the guest and incorrectly led us to conclude an absence of binding. However, simulations of EPR spectra combined with NMR data of reduced bTbk allowed showing inclusion complexation. EPR titrations were performed, and the corresponding binding constant was determined. 1 H NMR spectra with reduced bTbk suggested a shuttle mechanism, at nearly one equivalent of CB[8], for which the host moves rapidly between two stations.Molecules 2020, 25, 776 2 of 10 wealth of information, which, correctly extracted, can give users access to crucial information such as stability, structure, or dynamics, in various liquid or solid environments [8]. Supramolecular chemistry principally features diamagnetic compounds, but paramagnetic ones are expected to enable access to new types of applications including molecular magnetic switches [9], dynamic covalent systems [10], or tracers for imaging by stabilizing free radicals in reducing conditions. In the context of host•guest chemistry, the guests are almost exclusively [11] the radicals, and they are included in macrocyclic hosts. Several reviews [12][13][14] have already documented host•guest complexes featuring free radicals and several families of hosts including calixarenes, cyclodextrins, and cucurbiturils. This latter family of pumpkin-shape macrocycles [15][16][17][18][19] possess unique properties, in a broader context, such as ultrahigh binding [20,21], gas adsorption [22], or drug encapsulation and release [23,24]. With cucurbit[n]urils (CB[n]), the main radicals studied are nitroxides [25], in the majority of cases stable ones. In a seminal work, Lucarini and coworkers studied the cucurbit [7]uril (CB[7]) cavity by EPR spectroscopy using several nitroxides [26]. Later, Kaifer and coworkers showed how CB[n] could modulate the extent of spin exchange between covalently linked ...

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Section: Discussionmentioning

confidence: 99%

EPR Spectroscopy: A Powerful Tool to Analyze Supramolecular Host•Guest Complexes of Stable Radicals with Cucurbiturils

et al. 2020

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“…Through the inclusion within host molecules, the designed guest molecules can reside in or assemble in a rigid cavity, avoiding quenchers in the solution and suppressing free molecular motions. Our previous work utilized cucurbit[7]uril ( CB[7] ) to provide a confined cavity for a quinoline derivative with encoded green RTP emission signals in aqueous media . However, the short excitation wavelength and low RTP quantum yield limit the overall value of this approach for further applications in biology fields.…”

Section: Figurementioning

confidence: 99%

Visible‐Light‐Excited Room‐Temperature Phosphorescence in Water by Cucurbit[8]uril‐Mediated Supramolecular Assembly

et al. 2020

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Solid‐state materials with efficient room‐temperature phosphorescence (RTP) emissions have found widespread applications in materials science, while liquid or solution‐phase pure organic RTP emission systems has been rarely reported, because of the nonradiative decay and quenchers from the liquid medium. Reported here is the first example of visible‐light‐excited pure organic RTP in aqueous solution by using a supramolecular host‐guest assembly strategy. The unique cucurbit[8]uril‐mediated quaternary stacking structure allows tunable photoluminescence and visible‐light excitation, enabling the fabrication of multicolor hydrogels and cell imaging. The present assembly‐induced emission approach, as a proof of concept, contributes to the construction of novel metal‐free RTP systems with tunable photoluminescence in aqueous solution, providing broad opportunities for further applications in biological imaging, detection, optical sensors, and so forth.

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“…Supramolecular systems with improved host‐guest interactions have been a topic of growing research interest. Further, these host‐guest bindings are used to modulate the photophysical and photochemical properties of the various organic dyes . To date, variety of host systems such as cyclodextrins (CDs), calixarenes, octa‐acids, cucurbit[n]urils (CBns) are used to encapsulate the guest molecules .…”

Section: Introductionmentioning

confidence: 99%

Modulation of Twisted Intramolecular Charge Transfer Emission of 2‐(4′‐N,N‐Dimethylaminophenyl)imidazopyridines in Aqueous Cucurbit[7]uril⁺

2018

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The twisted intramolecular charge transfer (TICT) of 2‐(4′‐N,N‐dimethylaminophenyl)imidazopyridines (DMAPIPs) is examined in aqueous cucurbit[7]uril (CB7). The fluorescence spectral changes show the formation of a 1:1 inclusion complex between CB7 and DMAPIPs. Using the fluorescence data the association constants for DMAPIP‐CB7 complexes are also estimated. High stabilization energy obtained from DFT calculation corroborates the stability of DMAPIP‐CB7 complexes. The studies infer that imidazopyridine moiety of the DMAPIPs present inside the CB7 cavity and the dimethylamino phenyl ring is present outside in bulk water. The TICT emission is observed from both the DMAPIPs in CB7 environment too. The biexponential decay illustrated the dual emission of the DMAPIPs in aqueous CB7.

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A Cucurbit[7]uril Based Molecular Shuttle Encoded by Visible Room‐Temperature Phosphorescence

Cited by 82 publications

References 62 publications

EPR Spectroscopy: A Powerful Tool to Analyze Supramolecular Host•Guest Complexes of Stable Radicals with Cucurbiturils

EPR Spectroscopy: A Powerful Tool to Analyze Supramolecular Host•Guest Complexes of Stable Radicals with Cucurbiturils

Visible‐Light‐Excited Room‐Temperature Phosphorescence in Water by Cucurbit[8]uril‐Mediated Supramolecular Assembly

Modulation of Twisted Intramolecular Charge Transfer Emission of 2‐(4′‐N,N‐Dimethylaminophenyl)imidazopyridines in Aqueous Cucurbit[7]uril⁺

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A Cucurbit[7]uril Based Molecular Shuttle Encoded by Visible Room‐Temperature Phosphorescence

Cited by 82 publications

References 62 publications

EPR Spectroscopy: A Powerful Tool to Analyze Supramolecular Host•Guest Complexes of Stable Radicals with Cucurbiturils

EPR Spectroscopy: A Powerful Tool to Analyze Supramolecular Host•Guest Complexes of Stable Radicals with Cucurbiturils

Visible‐Light‐Excited Room‐Temperature Phosphorescence in Water by Cucurbit[8]uril‐Mediated Supramolecular Assembly

Modulation of Twisted Intramolecular Charge Transfer Emission of 2‐(4′‐N,N‐Dimethylaminophenyl)imidazopyridines in Aqueous Cucurbit[7]uril+

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Modulation of Twisted Intramolecular Charge Transfer Emission of 2‐(4′‐N,N‐Dimethylaminophenyl)imidazopyridines in Aqueous Cucurbit[7]uril⁺