Channels and Cavities Lined with Interlocked Components: Metal‐Based Polyrotaxanes That Utilize Pyridinium Axles and Crown Ether Wheels as Ligands

Abstract

The formation of polyrotaxanes by metal±ligand self-assembly is a viable method for the programmed organization of mechanically linked molecular components into a repeating framework. This has significant potential for producing materials that contain functional molecular entities that may be addressable or controllable. [1] The challenges of designing, synthesizing, and crystallizing such materials are many and manipulation easily aligns a single tube in an arbitrary direction. For demonstration we have further written the word ™tube∫, as shown in Figure 5.In summary, we found that the glycolipid nanotube could be a good candidate for a cytomimetic tubule in terms of its mechanical properties. Moreover, exploiting the moderate rigidity, we have developed a novel but simple aligning method: a fine line of the single nanotube is drawn freely simply by microextruding the aqueous dispersion on glass plate. Our manipulation methodology promises to open up fascinating possibilities for lipid nanotubes beyond only a substitute for microtubules; for example, a nanoneedle could be realized by extruding half of the single nanotube and fixing it at the tip of a microextrusion needle; also bridging or branching of the nanotubes on glass or metal substrates might be used as a mold for the formation of a wire and hub inside them, in molecular electronic devices; lastly, a single nanotube channel and its assembled array should provide 1D nanospace for the separation of advanced macromolecules beyond the submicro total analysis system (submTAS). Experimental SectionPreparation of single lipid nanotubes: These were prepared in water through self-assembly of renewable-resource-based, synthetic glycolipid cardanyl-b-d-glucopyranoside, which is a mixture of 1-O-3'-n-(8'(Z),11'(Z), 14'-pentadecatrienyl)-phenyl-b -d-glucopyranoside (ca. 29 wt %), 1-O-3'-n-(8'(Z),11'(Z)-pentadecadienyl) phenyl-b-dglucopyranoside (ca. 16 wt %), 1-O-3'-n-(8'(Z)-pentadecenyl) phenylb-d-glucopyranoside (ca. 50 wt %), and 1-O-3'-n-(pentadecyl) phenyl-b-d-glucopyranoside (ca. 5 wt %), as reported elsewhere. [17] Nanotube structures with 10±15 nm inner diameter and high axial ratios were confirmed by TEM, field-emission scanning electron microscopy (FE-SEM), confocal laser scanning microscopy, and atomic force microscopy (AFM). On the basis of X-ray diffraction studies, the tubular membrane wall consists of three to four interdigitated lipid bilayers. Combination of a hydrogen-bond network between the glucose headgroups, p±p stacking interactions between phenyl rings, and hydrophobic interactions between long alkyl chains are responsible for the stabilization of noncovalently formed nanotube architectures.

Rotaxanes as ligands: from molecules to materials

“…The reaction of two equivalents of A1 (as the BF 4 salt) with four equivalents of DB24C8 and one equivalent of [M(H 2 O) 6 ][BF 4 ] 2 (M 5 Cu, Cd, Ni) in MeNO 2 produced X-ray quality crystalline material (average yields y80%). 33 Fig. 13 (top) shows how the use of these metal ions in a non-coordinating solvent allows for an octahedral coordination geometry comprising four RL1 linkers in a square planar arrangement, along with one water molecule and Fig.…”

“…This, combined with a trans geometry at the metal ion, produces a linear 1D MORF with Co … Co 22.1 Å . 33 This polymer can be viewed as a metalligand ''wire'' in which the crown ethers act as a protective coating analogous to the use of long-chain hydrocarbons attached to phosphine ligands to surround metal polyacetylene linkages. 34 This MORF also contains infinite channels parallel to the polymer chains which are filled with anions and solvent.…”

“…The interlayer spacings are 12.0 and 10.0 Å , with the layers stacked in a pattern that gives rise to an open framework material with large infinite channels lined with crown ethers. The channels are filled with anions and solvents; there are 15 molecules of MeNO 2 per Cd(II) ion.Calculations estimate that the accessible void space occupied by anions and solvent is 50%; 38% for solvent only 33. …”

A New [2]Pseudorotaxane from 1,2-Bis(isoquinolinium)ethane Salt/Dibenzo-24-crown-8 Ether

“…They have widely been applied for the construction of supramolecular architectures with charming topological geometry. The motif of 1,2-bis(pyridinium)ethane=crown ether has originally been demonstrated by Loeb and Wisner [1][2][3][4][5] and further employed to construct many metal-organic rotaxane frameworks (MORFs) [6][7][8]. Herein, an analog 1,2-bis(isoquinolinium)ethane is shown as an axle to thread through the cavity of the dibenzo-24-crown-8 (DB24C8) ether, forming a [2]pseudorotaxane, and it further packs to form supramolecular bricklaying [9].…”

Electrochemically addressable trisradical rotaxanes organized within a metal–organic framework

“…By integrating such rudimentary molecular switches within highly ordered MOFs, however, they can be organized periodically and precisely in 3D space, allowing their otherwise incoherent motions to be rectified. Although steady progress has been made (17)(18)(19)(20)(21)(22)(23)(24)(25)(26) toward this goal in recent years, it still remains a considerable challenge to design such systems that can be addressed by stimuli in the solid state. Electrochemical potential and light would be particularly appealing stimuli on account of their ease of interfacing with current technologies.…”