Molecularly Defined Shape‐Persistent 2D Oligomers: The Covalent‐Template Approach to Molecular Spoked Wheels

Mössinger, Dennis; Hornung, Jens; Lei, Shengbin; Feyter, Steven De; Höger, Sigurd

doi:10.1002/ange.200701614

Cited by 15 publications

(10 citation statements)

References 55 publications

(17 reference statements)

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“…Inorganic alumina platelets have been self‐assembled into wagon‐wheel shaped structures that are incorporated into plastics to improve their barrier and mechanical properties. This was the first time large wheel‐shaped molecules had been formed (Mossinger and others 2007).…”

Section: Nanocomposites and Other Emerging Nanotechnologies In Food Pmentioning

confidence: 98%

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Brody¹,

Bugusu²,

Han³

et al. 2008

Journal of Food Science

412

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Section: Nanocomposites and Other Emerging Nanotechnologies In Food Pmentioning

confidence: 98%

Scientific Status Summary

Brody¹,

Bugusu²,

Han³

et al. 2008

Journal of Food Science

412

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“…Scheme 1 presents the straightforward synthetic pathway to all-covalent 2D oligo(phenyl-A C H T U N G T R E N N U N G ene-ethynylene-butadiynylA C H T U N G T R E N N U N G ene)s (2D-OPEBs) relying on a highyield template-directed sixfold acetylene dimerization in the final step. [24] Our approach paves the way to molecularly defined 2D structures that are well characterizable, allow introduction of functionality at the rim as well as above and below the molecular plane, and can be obtained in different sizes. Unlike the abovementioned cutouts of graphite, graphyne, or graphdiyne, our approach is not restricted to structural ideals, but can be adapted to synthetic feasibility as well as improved solubility and surface patterning properties.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, the molecule is so big that its diffusion on the surface is quite slow at room temperature, and even isolated molecules could be observed by STM with reasonable resolution. [24] …”

mentioning

confidence: 97%

Two‐Dimensional Oligo(phenylene‐ethynylene‐butadiynylene)s: All‐Covalent Nanoscale Spoked Wheels

Lei

Heyen

Feyter

et al. 2009

Chemistry A European J

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Round and round: Covalently bound spokes induce an efficient template-directed cyclization towards a rigid molecular wheel (see figure) and afford dramatically increased shape-persistence properties compared with non-strutted macrocycles.The synthesis and characterization of a shape-persistent two-dimensional (2D) organic compound is described in detail. In a rational modular synthesis of a dodecaacetylene precursor and its subsequent template-aided cyclization, we obtained a molecularly defined, stable, C(6)-symmetric, rigid, spoked wheel. Peripheral tert-butyl groups and alkyl chains attached to the plane of the molecule provide sufficient solubility, so that the 2D oligomer can be fully characterized by MALDI-MS, GPC, and (1)H NMR, UV/Vis absorption, and fluorescence spectroscopy. Molecular mechanics and dynamics simulations indicate that the most stable conformer of the molecule in vacuum is a shallow boat conformation with a small dihedral angle. Comparisons with the precursor as well as a ring-only structure clearly reveal the high rigidity of the title compound. Small-angle neutron scattering (SANS) experiments in [D(8)]THF and CDCl(3) affirm the rigid backbone structure in solution, that is, a radius of about 2.7 nm and a thickness of about 0.22 nm. STM investigations illustrate that the wheel molecules adsorb with their molecular plane parallel to the surface and can form hexagonal crystalline domains (unit cell parameters are a=b=6.0+/-0.2 nm and theta=60+/-2 degrees ), with the tert-butyl groups on the apexes staggered. Such staggering induces chirality in the organized domains. AFM investigations demonstrate that the wheel molecules inside overlayers organize in the same way as in the layer directly in contact with the surface. This indicates an epitaxial growth characteristic of the film.

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“…[1][2][3][4][5][6][7][8][9][10][11][12] Recently, we developed the concept of Vernier templating-the use of noncommensurate combinations of templates and building blocks to direct the formation of cyclic oligomers, such that the number of binding sites in the product is the lowest common multiple of the numbers of sites in the template and the starting material. [1][2][3][4][5][6][7][8][9][10][11][12] Recently, we developed the concept of Vernier templating-the use of noncommensurate combinations of templates and building blocks to direct the formation of cyclic oligomers, such that the number of binding sites in the product is the lowest common multiple of the numbers of sites in the template and the starting material.…”

mentioning

confidence: 99%

Two Vernier‐Templated Routes to a 24‐Porphyrin Nanoring

Kondratuk¹,

Perdigão²,

O’Sullivan³

et al. 2012

Angew Chem Int Ed

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Dedicated to Professor Fraser Stoddart on the occasion of his 70th birthdayIngenious new template-directed strategies make it possible to synthesize an increasingly wide range of molecular architectures, which would otherwise be inaccessible. [1][2][3][4][5][6][7][8][9][10][11][12] Recently, we developed the concept of Vernier templating-the use of noncommensurate combinations of templates and building blocks to direct the formation of cyclic oligomers, such that the number of binding sites in the product is the lowest common multiple of the numbers of sites in the template and the starting material. [12d] This principle allows a small template to direct the formation of a much larger macrocycle. Previously, we illustrated this idea with the synthesis of a 12-porphyrin nanoring, c-P12, from a linear zinc porphyrin tetramer, l-P4, and a hexapyridyl template, T6.Here we report the synthesis of a 24-porphyrin ring, c-P24, by two Vernier-templated routes: a) coupling the linear porphyrin octamer l-P8 in the presence of hexapyridyl template T6, and b) coupling the linear porphyrin hexamer l-P6 in the presence of the octapyridyl template T8 (Scheme 1). The 24porphyrin nanoring can be prepared in yields of up to 25 %. It has a diameter of 10 nm, as confirmed by scanning tunneling microscopy (STM), and a molecular weight of 26 kDa, thus placing it in the size range of a typical protein. This flexible macrocycle can be locked into a planar p-conjugated conformation by the cooperative self-assembly of a 2:24 doublestrand complex with the linear diamine ligand 1,4diazabicyclo[2.2.2]octane (DABCO).The representation of the two routes to c-P24 in Scheme 1 overlooks the fact that complexes such as (l-P8) 3 ·(T6) 4 and c-P24·(T6) 4 have many possible isomers, as illustrated in Figure 1. However, the formation of these isomeric intermediates should not detract from the efficiency of the Vernier-templated synthesis, because removal of the template will convert all these isomers into the same c-P24 open ring (except for knotted structures, for example, Figure 1 d [13] ).Palladium-catalyzed oxidative coupling of the linear porphyrin octamer l-P8 [12a] in the presence of the hexapyridyl template T6 [12b,c] gave the expected product c-P24, together with the 16-porphyrin ring c-P16 [14] and linear polymers, all as complexes with T6. The polymeric by-products were removed Scheme 1. a) Vernier-templated synthesis of the nanoring c-P24. Reagents: 1) [PdCl 2 (PPh 3 ) 2 ], CuI, benzoquinone, iPr 2 NH; 2) pyridine. b) Structures of T6, T8, and c-P24; Ar = 3,5-bis(octyloxy)phenyl. Figure 1. Four examples of possible isomers of c-P24·(T6) 4 . [13]

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Molecularly Defined Shape‐Persistent 2D Oligomers: The Covalent‐Template Approach to Molecular Spoked Wheels

Cited by 15 publications

References 55 publications

Scientific Status Summary

Scientific Status Summary

Two‐Dimensional Oligo(phenylene‐ethynylene‐butadiynylene)s: All‐Covalent Nanoscale Spoked Wheels

Two Vernier‐Templated Routes to a 24‐Porphyrin Nanoring

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