Template‐Directed Synthesis of a π‐Conjugated Porphyrin Nanoring

Hoffmann, Markus; Wilson, Craig J.; Odell, Barbara; Anderson, Harry L.

doi:10.1002/anie.200604601

Cited by 208 publications

(125 citation statements)

References 37 publications

(26 reference statements)

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“…We investigated the palladium-catalysed oxidative coupling of the linear zinc-porphyrin 10-mer l-P10 in the presence of hexa-pyridyl template T6 23,34 and octa-pyridyl template T8 35 ( Fig. 1).…”

Section: Resultsmentioning

confidence: 99%

Supramolecular nesting of cyclic polymers

et al. 2015

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Monodisperse cyclic porphyrin polymers, with diameters of up to 21 nm (750 C-C bonds), have been prepared using Vernier template-directed synthesis. The ratio of the intrinsic viscosities for cyclic and linear topologies is 0.72, indicating that these polymers behave as almost ideal flexible chains in solution. When deposited on gold surfaces, the cyclic polymers display a new mode of two-dimensional supramolecular organisation, combining encapsulation and nesting: one nanoring adopts a near-circular conformation thus allowing a second nanoring to be captured within its perimeter, in a tightly folded conformation. Scanning tunnelling microscopy reveals that nesting occurs in combination with stacking when nanorings are deposited under vacuum, whereas when they are deposited directly from solution under ambient conditions, there is stacking or nesting, but not a combination of both.The tertiary structures of biological macromolecules are achieved through folding, coiling and multiplex formation, driven by the cooperative effect of many weak interactions 1 . Synthetic monodisperse macromolecules with similar cooperative folding behaviour provide a viable approach to the programmed fabrication of 3D nanostructures [2][3][4][5] . Here we show that cyclic porphyrin polymers, with molecular weights of 30-60 kDa, self-assemble into nested structures on a gold surface. These nested assemblies are only observed when the cyclic polymer has 30 or more repeat units, in keeping with the predictions of a simple geometrical model.The importance of non-covalent self-assembly in biology has inspired many studies of supramolecular organisation on surfaces [6][7][8] , generating 2D assemblies with progressively escalating complexity, from early work on simple structures such as clusters 9 and rows 10,11 , to nanoporous arrays 12,13 , host-guest architectures [14][15][16] , hierarchical arrangements 17 , and multicomponent assemblies [17][18][19] . However, cooperative conformational control has proved difficult to achieve, and this remains a significant gulf between artificial and biological systems. One reason for this difference is that biological macromolecules are much more flexible than the component molecules studied in 2D supramolecular assemblies which are small and, with some exceptions 20,21 , are often treated as quasi-rigid building blocks. Here we illustrate how interactions between large flexible molecules can result in biomimetic cooperative conformational organisation.Studies of linear and cyclic butadiyne-linked zinc porphyrin oligomers (structures l-PN THS and c-PN, Fig. 1) have shown that the distance between the centres of the porphyrin units along the chain is a = 1.35 nm 5,22,23 . Thus the contour length of a linear oligomer, or the perimeter of a nanoring, is Na, where N is the number of porphyrin repeat units. Previously we have shown that nanorings adsorbed on Au(111) exhibit flexibility [24][25][26] , and also that they can act as nanoscale traps for other adsorbed species, such as C 60 guest molecules 2...

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Section: Resultsmentioning

confidence: 99%

Supramolecular nesting of cyclic polymers

et al. 2015

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“…Expanded porphyrins have attracted considerable attention, in part because of their large conjugated p-system and flexible conformation leading to unique spectral, electrochemical and coordination properties , and in part they have wide potential applications in the fields of functional materials, molecular wires and near-infrared dyes [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45]. Hexaphyrins are an example of expanded porphyrins which contain six pyrrole rings in the macrocycle and possess a sufficiently large porphyrin cavity to allow for the coordination of two metal ions and the formation of dinuclear metal complexes.…”

Section: Introductionmentioning

confidence: 99%

Electrochemistry and spectroelectrochemistry of metallohexaphyrins containing bis-copper or bis-zinc central metal ions

Chen

Ren

et al. 2017

J. Porphyrins Phthalocyanines

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ABSTRACT:Two meso-substituted bis-metallohexaphyrins were synthesized and characterized as to their electrochemical and spectroelectrochemical properties in nonaqueous media. The examined compounds are represented as HexaPyM 2 , where HexaPy represents an expanded macrocycle containing six pyrroles and M = Cu(II) or Zn(II). Each hexaphyrin undergoes four reversible one-electron reductions and two irreversible oxidations in PhCN or CH 2 Cl 2 containing 0.1 M tetrabutylammonium perchlorate. The HexaPyCu 2 is much easier to reduce than the corresponding Cu porphyrin with the same meso-substituents and it is also easier to reduce than a structurally related Cu(II) tripyrrinone. 4-, respectively. The neutral HexaPyCu 2 and HexaPyZn 2 also exhibit two oxidations, both of which are irreversible at a scan rate of 0.10 V/s. The peak separation between the first one-electron addition and the first electron abstraction of HexaPyM 2 ranges from 1.46 to 1.72 V. These non-thermodynamic HOMO-LUMO gaps are similar to the range of HOMO-LUMO gaps for previously characterized sapphyrins which contain five pyrrole ring in the macrocycle. KEYWORDS

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“…Since the pioneering work of Sanders and Anderson, [4] several CPOs in which the individual porphyrin rings are connected by covalent bonds have been reported. [5][6][7][8][9][10] CPOs have also been investigated in other fields such as host-guest chemistry and single molecule photochemistry. [7] We are interested in covalently linked arrays in which the bridging units are fully conjugated with the porphyrin π-system, including CPOs.…”

Section: Introductionmentioning

confidence: 99%

“…Since the first conjugated diporphyrin system, a butadiyne-linked dimer, [11] was synthesised, many other porphyrin systems that offer strong electronic communication through their conjugated linkers have been investigated. The butadiyne and other linkers have been studied extensively, with numerous papers reporting interesting results with potential in various fields, [7,10, including recently two-photon absorption [31,34,[37][38][39][40][41][42][43][44] and two-photon photodynamic therapy. [14,15,41,45] Anderson suggested that an azo linkage would provide the optimum degree of interporphyrin conjugation and be a good bridge for facilitating electronic communication between the porphyrins in the ground state.…”

Section: Introductionmentioning

confidence: 99%