Hydrogen‐Bonding Receptors for Molecular Guests

Wilson, Andrew J.

doi:10.1002/9780470661345.smc071

Cited by 2 publications

(2 citation statements)

References 85 publications

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“…These findings open new applicative horizons for the BN doping of polyaromatic hydrocarbons in supramolecular chemistry, for which the ability to form H-bonding interactions at the periphery can be exploited both in solution and at the solid state . In addition, the ease of preparing these BN-doped PAHs makes these heterocycles interesting to organic, supramolecular, and materials chemists who are incessantly looking for programmable synthetic strategies for digitizing molecules displaying multifunctional and self-organization properties exploitable in materials science and biology …”

Section: Discussionmentioning

confidence: 99%

Probing Peripheral H-Bonding Functionalities in BN-Doped Polycyclic Aromatic Hydrocarbons

et al. 2020

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The replacement of carbon atoms at the zigzag periphery of a benzo[fg]tetracenyl derivative with an NBN atomic triad allows the formation of heteroatom-doped PAHs isosteres, which expose BN mimics of the amidic NH functions. Their ability to form H-bonded complexes has never been touched so far. Herein we report the first solution recognition studies of peripherally NBN-doped PAHs to form doubly H-bonded DD•AA and ADDA•DAAD-type complexes with suitable complementary H-bonding acceptor partners. The first determination of the Ka in solution showed that the 1:1 association strength is around 27 ± 1 M-1 for the DD•AA complexes in C6D6, whereas it rises to 1820 ± 130 M-1 for the ADDA•DAAD array in CDCl3. Given the interest of BNdoped polyaromatic hydrocarbons in supramolecular and materials chemistry, it is expected that these findings will open new possibilities to design novel materials, where the H-bonding properties of peripheral NH hydrogens could serve as anchors to tailor the organizational properties of PAHs. INTRODUCTION Following the vigorous synthetic developments of polycyclic aromatic hydrocarbons (PAHs), 1 the substitution (i.e., doping) of sp 2-carbon atoms with isoelectronic and isostructural BN couples is re-emerging as a versatile approach to tune the optoelectronic properties of these materials. 2-7 In particular, borazines 8,9 and BN-doped PAHs (e.g., azaborines, 10,11 borazapyrenes, 12,13 borazaphenanthrenes 12,14 borazanaphthalenes, 15,16 borazaanthracene 17,18 and boraazaperylene 19) are now increasingly attracting the attention of the physical and chemical community for their use in a broad spectrum of optoelectronic applications. 20-22 When used to decorate a periphery, nonsubstituted BN couples terminate with NH functions that, being more acidic than the CH analogues, could engage into H-bonding interactions as observed with boronic acids. 23 For instance, Liu and co-workers showed in a seminal report that 1,2-dihydro-1,2-azaborine can act as an H-bonding donor in the solid state and engage into a H-bond with the C=O

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Section: Discussionmentioning

confidence: 99%

Probing Peripheral H-Bonding Functionalities in BN-Doped Polycyclic Aromatic Hydrocarbons

et al. 2020

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“…Thereby, a weak hydrogen bond acceptor is converted into a strong hydrogen bond donor. Our idea was therefore to exploit hydrogen bonds, which are among the strongest noncovalent interactions, − as a driving force for the conformational switching process. This could be accomplished by placing suitable hydrogen bond acceptor groups on the quinoxaline walls of a diquinone cavitand (Figure A).…”

Section: Development Of Redox-switchable Cavitandsmentioning

confidence: 99%

Development of Redox-Switchable Resorcin[4]arene Cavitands

2014

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CONSPECTUS: Within the framework of miniaturization of electromechanical devices, the development of a redox-switchable molecular gripper as a tool for nanorobotics is appealing both from an academic and from a practical perspective. Such a tool should be able to controllably grab a molecular cargo, translocate it over considerable distances and time scales, and release it. Resorcin[4]arene cavitands seem to be an ideal platform for the development of molecular grippers due to their ability to adopt two spatially well-defined conformations: an expanded kite and a contracted vase. Furthermore, they possess "legs" for functionalization and attachment to metal surfaces. While changes in temperature, pH, and metal-ion concentration were known to induce conformational switching, redox-switchable cavitands remained a challenge. In this Account, we describe our efforts toward the development of a new class of resorcin[4]arene cavitands that are redox-switchable. First, we introduced the naphthoquinone moiety as a redox-active wall component and showed that cavitands containing four quinone walls strongly prefer the open kite conformation in both the quinone and hydroquinone redox states, while cavitands that contain two quinone and two quinoxaline walls can adopt both the vase and the kite conformations depending on solvent but not on redox state. Next, in order to introduce a driving force for the conformational switching process in diquinone cavitands, we designed cavitands with hydrogen bond acceptor groups on the quinoxaline walls. These acceptors were sought to establish hydrogen bonds with the hydroquinone groups in the reduced redox state, thereby stabilizing the vase form. Oxidation to the quinone state would remove these interactions, switching the cavitand back to the kite form. Cavitands equipped with different hydrogen bond acceptor groups were synthesized and evaluated. We found that carboxamide moieties are best suited to assist redox-induced switching of conformational and binding properties. With the goal of further increasing association constants and reducing guest-exchange rates via steric congestion, we exchanged the naphthoquinone with the triptycene-quinone moiety. The congesting influence of the triptycene-quinone moiety on the binding properties was quantified both in the presence and in the absence of additional hydrogen bond interactions that stabilize the vase form. X-ray crystallographic studies provided insights into the solid-state structures of the cavitands in different solvents and redox states. A significant enhancement of association constants and reduction in guest release rates was observed in the reduced redox state compared with the top-open system, yielding redox-switchable cavitand baskets. These studies represent a step towards the development of redox-switchable molecular grippers on metal surfaces. Future challenges will consist in the development of cavitands that will no longer rely on an external proton source for the switching process, allowing redox-switching to be perfor...

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Hydrogen‐Bonding Receptors for Molecular Guests

Cited by 2 publications

References 85 publications

Probing Peripheral H-Bonding Functionalities in BN-Doped Polycyclic Aromatic Hydrocarbons

Probing Peripheral H-Bonding Functionalities in BN-Doped Polycyclic Aromatic Hydrocarbons

Development of Redox-Switchable Resorcin[4]arene Cavitands

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