Self-assembly helicates

Figure 5.11 Confocal laser scanning micrographs of self-assembled helical fibers made of glucosamide bolaamphiphiles Glc-NC( )CN-Glc (14) (a) n = 6, (b) n = 10, and (c) n = 12. Reprinted from Ref. 53 with permission of Wiley-VCH.

Figure 5.15 Dark-field optical micrograph of self-assembled helical filaments from an aqueous dispersion of 2Ci2-L-GluCnN+ (22) after aging for 30 h. Bar = 10 xm. Reprinted with permission from Ref. 74. Copyright 1985 by the American Chemical Society.

Lehn and coworkers also discussed the principles of design of self-assembling helical structures on the basis of conformational control. Depending on the solvent used, they were able to obtain helicate fibers and bundles possessing extended molecular channels characterized by hollow cores of limited diameter ofca. 8 A. This finding could form the basis of functional materials for multichannel ion active transport [28]. 

Calculations by the MNDO (modified neglect of diatomic overlap) method with full optimization of geometry were carried out for [Zn, N, C, H]+ ions indicating the possible existence of four stable isomers (Figure 7). According to the same semi-empirical method, [Zn, N, C2, H3]+ ions can form nine stable isomeric stmctnres (Fignre 7) In a separate study by density functional theory, self-assembled helicate architectures have been proposed for ions of the [Zn (CN)2 +i] series. ... 

Synthetic strategy, classification, and properties of self-assembled helicates... 

Transparent film of T-CNs [Fig. 13.8] was cast from the suspensions of T-CNs at ambient conditions that retain the self-assembled helical order formed in the N -LCs [Fig. 13.9],... 

K. Suda, K. Akagi, Self-assembled Helical conjugated poly(mcto-phenylene) derivatives that afford whiskers with Discotic Hexagonal columnar packed structure. Macromolecules 44, 9473-9488 (2011)... 

K. Suda, J. Yoshida, S. Nimori, K. Akagi, Hierarchical stractures of self-assembled helical conjugated polymers - magnetically forced alignment of liquid crystalline poly(meto-phenylene) derivatives. Synth. Met. 159, 943-948 (2009)... 

Figure 8.3 Natural (a, b) and synthetic (c, d) nanopattems that offer templates for MSC differentiation and self-renewal (a) Type X collagen and (b) fenestrated sinusoidal capillaries, (c) dip-pen patterned nanoislands (70 nm diameter with 28 mn center-center spacing) that retain MSC multipotency, and (d) self-assembled helical amphiphUe with 63 nm periodicity that stimulates MSC osteogenesis.

Zhan C., Gao P., Liu M., Self-assembled helical spherical-nanotubes from an L-glutamic acid based bolaamphiphUic low molecular mass organogelator, Chem. Commun., 4, 2005,462-464. 

Keywords Chirality Gels Self-assembly Helices Fibers... 

Kobayashi investigated a self-assembled boronic ester cavitand capsule for photochemical reaction of 2,6-diacetoxyanthracene. Tsuda found a self-assembled helical anthracene nanofiber in a vortex. Chou examined rotational behaviors and fluorescence energy transfer of N-l- and N-2-anthryl succinimide derivatives. " Reversible photoinduced twisting of molecular crystal microribbons via [4 - - 4] photocycloaddition of 9-anthra-cenecarboxylic acid. Reversible single walled carbon nanotubes of 1,3-bis(9-anthracenylmethyl)imidazolium chloride was examined as a functionalized anthracene salts.Karatsu reported the intramolecular photodimerization of 9-substituted anthracene derivatives (253) tethered by oligosilanes giving [4 + 4] and [2 - - 4]cycloadducts (254), (255), and (256). ... 

In some cases, nanoscale chirality can be observed by using electron microscopy methods, for example, in the form of self-assembled helical fibrils/fibers. It has been reported that using opposite enantiomers as gelators can give rise to fibers with opposite heUcities (Figure 1). In this way, chirality on the molecular scale is directly translated into chirahty on the nanoscale. 

The chiral polymers ((5 )-30 and (i )-30) showed circularly polarized fluorescence because the backbone of the helix was conjugated. They also showed a linear polarized fluorescence after macroscopic alignment. X-ray diffraction (XRD) analysis showed that the whiskers were composed of hexagonally packed columns of self-assembled helices, uniaxially packed parallel to the long axis of the whiskers. 

Watanabe K, Suda K, Akagi K (2013) Hierarchically self-assembled helical aromatic conjugated polymers. J Mater Chem C l(16) 2797-2805. doi 10.1039/c3tc00045a... 

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