Abstract

Abstract

Abstract

Abstract

The complexing behaviour of two linear compounds 1 and 2 toward the trifluoroacetic acid (TFA) salts of n-dodecylamine, di-n-octylamine, n-dodecyl D- and L-phenylalaninates (3, 4, and D- and L-5) in chloroform has been described. Compounds 1 and 2 consist of two folded amide moieties with two pyridyls at the terminals which are connected directly or with an acetylene linker. The rigidified folded moieties are stabilized by intramolecular hydrogen bonding, while the whole molecules can adopt an "S"- or a "C"-styled conformation depending on the relative orientation of the two rigidified moieties. ¹H NMR, UV-Vis, fluorescent and circular dichroism investigations revealed that 1 and 2 could bind primary and secondary ammonium cations with their "C"-styled conformation. In the presence of 1 equiv. of TFA, the binding stability was increased significantly as a result of promoted formation of the "C"-styled conformation due to the monoprotonation of the peripheral pyridyl units in 1 and 2. In contrast, the addition of 2 equiv. of TFA substantially weakened the binding stability because the "S"-styled conformation was favored as a result of protonation of both of their pyridyl units. Moreover, remarkable induced circular dichroisms were also displayed for the complexes of 1 and 2 with chiral D- and L-5.

The stacking interactions between F⋅⋅⋅HN hydrogen-bonded foldamers 1–3, bis-foldamer 4, and tris-foldamer 5 and C₆₀ and C₇₀ are described. Compound 4 contains two folded units, which are connected by an isophthalamide linker, whereas 5 has a C₃-symmetrical discotic structure, in which three folded units are connected by a benzene-1,3,5-tricarboxamide unit. UV/Vis, fluorescence, and NMR experiments have revealed that the foldamers or folded units strongly stack with fullerenes in chloroform. The (apparent) association constants of the respective complexes have been determined by a fluorescence titration method. The strong association is tentatively attributed to intermolecular cooperative fluorophenyl⋅⋅⋅π and solvophobic interactions. A similar but weaker interaction has also been observed between an MeO⋅⋅⋅HN hydrogen-bonded foldamer and fullerenes. AFM studies have revealed that the surfaces of 3 and 4 show fibrous networks, while the surface of 5 shows particles. In sharp contrast, mixtures of 3 and 4 with C₆₀ have been shown to generate thinner separated fibrils, whereas a mixture of 5 and C₆₀ produces honeycomb-like nano networks, for which a columnar cooperative stacking pattern is proposed. The results demonstrate the usefulness of F⋅⋅⋅HN hydrogen-bonded folded structures in the construction of nanoscaled materials.

A new series of hydrogen bonding-driven heterodimers have been self-assembled in chloroform from hydrazide-based monomers. Additional intermolecular donor-acceptor interaction between the electron-rich bis(p-phenylene)-34-crown-10 unit and the electron-deficient naphthalene diimide unit has been utilized to increase the stability of the dimmers, and pronounced cooperativity of the two discrete non-covalent forces to stabilize the dimer has been revealed by the quantitative ¹H (2D) NMR and UV-Vis experiments.

Two series of stable and soluble fulleropyrrolidines have been prepared from the reactions of C₆₀, glycine or its N-arylated derivatives and aliphatic aldehydes or ketones in refluxing toluene or chlorobenzene. The new C₆₀ derivatives represent new useful building blocks for further preparation of more funcionalized C₆₀ derivatives.

Hohe asymmetrische Verstärkung tritt bei einer neuen Klasse von wasserstoffverbrückten Foldameren aus Zinkporphyrineinheiten und C₆₀-verknüpften chiralen Histidinen auf. Zwei Arten nichtkovalenter Wechselwirkungen sind strukturbildend: Zinkporphyrin-Imidazol-Koordination und π-π-Stapelung zwischen Zinkporphyrin und C₆₀ (siehe Bild).

With an increasing number of folding and helical structures available, chemists have begun to pay greater attention to the functions of this family of structurally unique oligomers. Hydrogen-bonding-mediated aromatic oligoamide foldamers have the features of good structural predictability, synthetic facility, and structural modification, which make them very promising as scaffolds or platforms for supramolecular chemistry. Recent advances in the applications of this class of shape-persistent oligomers in the promoted synthesis of macrocycles, design of new nonring receptors, supramolecular self-assembly, molecular encapsulation, and reaction acceleration, are highlighted in this Focus Review.

Intramolekulare F⋅⋅⋅H-N-Wasserstoffbrücken wurden erstmals zum Aufbau einer Reihe von Foldameren aus aromatischen Amiden genutzt (siehe Bild; R¹=H, Me; R²=CON(n-C₈H₁₇)₂). Die so erhaltenen sichelförmigen und helicalen Architekturen sind gute Acceptoren für Dialkylammoniumionen.

One linear template 13 and one cyclophane template 15, both incorporating two electron rich 1,4-dialkoxybenzene units and one diamide unit, have been synthesized. By utilizing donor-acceptor interaction and/or intermolecular hydrogen bonding assembling principles, one novel hetero[3]rotazane 22·4Cl, possessing one neutral and one tetracationic ring components, has been synthesized from 13, through neutral [2]rotaxane 21 as intermediate. With 15 as template, tetracationic [2]catenane 23·4PF₆ was assembled by using donor-acceptor interaction, but no neutral [2]rotaxane could be obtained under the typical conditions of hydrogen bonding assembling principle. The interlocked supramolecular compounds have been characterized and their spectral properties are investigated.