A Fluorescent Ditopic Rotaxane Ion‐Pair Host

Abstract

We report a rotaxane based on a simple urea motif that binds Cl− selectively as a separated ion pair with H+ and reports the anion binding event through a fluorescence switch‐on response. The host selectively binds Cl− over more basic anions, which deprotonate the framework, and less basic anions, which bind more weakly. The mechanical bond also imparts size selectivity to the ditopic host.

Direct Detection of Hydrogen Bonds in Supramolecular Systems Using 1H-15N HMQC

“…Hydrogen-bonding was implied between the bipyridinium macrocycle and neutral axle in previously reported X-ray structures. 56,64 The hydrogen-bond may not be observed here due to chemical exchange line broadening on either the J-coupling, transverse relaxation rate (R2) or chemical shift difference time scales. Alternatively, the dominant structure in solution may differ from that observed in the solid-state Correlation between the hydrogen attached to N d and the protons on the alkyl chain of the urea side chain was also observed.…”

Reversibly modulating a conformation-adaptive fluorophore in [2]catenane

“…Considering the close spatial distance between electron-donor DPAC fluorophore and electron-acceptor MTA secondary site, the fluorescence quenching after deprotonation was attributed to the intramolecular photo-induced electron-transfer (PET) effect by DFT calculation (Figure S55). [55][56][57][58] Meanwhile, the secondary MTA unit bound the DPAC-ring by ion-dipole interaction (Figures S34-S38 and S49), which also produced a ring tension to confine the vibrational motion of the DPAC fluorophore. The combination of PET and intrinsic conformational effects of DPAC, leads to the slightly shifted fluorescent wavelength of Catenane 7-H, which also exhibited an excellent reversibility (~8.5% loss of switching integrity, Figure S56) owing to the confinement of mechanical bonds.…”

Dynamic Metalloporphyrin‐Based [2]Rotaxane Molecular Shuttles Stimulated by Neutral Lewis Base and Anion Coordination

“…Recent years have witnessed the exploitation of mechanically interlocked molecules (MIMs) in a diverse range of applications including molecular recognition, [1–6] sensing [7–10] and catalysis, [11–14] wherein the unique microenvironment or topology of the mechanical bond underpins the functional behaviour of the system [15–18] . The exquisite topological control afforded by the mechanical bond in MIMs frequently affords enhanced host‐guest binding behaviour, with increased selectivity and binding affinities over their non‐interlocked analogues [19] …”