Do Catechol Derivatives Electropolymerize?

Voisin, Emilie; Williams, Vance E.

doi:10.1021/ma800320j

Cited by 21 publications

(12 citation statements)

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“…More recently, the electrochemical polymerization of catechol and its derivatives was reported to give poly(ophenylene)s, 9 but these studies have subsequently been questioned and it is likely that only triphenylene-like molecules result from these reactions. 10 The most direct parallels to the work reported in this paper are Ito's poly(2,3-quinoxaline)s 11 and Simpkins' synthesis of a genuine series of o-phenylene oligomers (up to the nonamer). 12 Both of these systems exhibit well-defined, but very different, secondary structures: unlike the rod-like p-phenylenes, ophenylenes have the potential for a rich conformational behavior, as the backbone can assume a variety of distinct conformational states due to hindered rotation and torsional biases about the biaryl bonds.…”

Section: Introductionmentioning

confidence: 59%

“…Quantum yields were determined relative to DPA (Φ ) 0.90) following the established procedure. 32 The quantum yield for oP 4 is comparatively low (Φ ) 0.040), but for the remaining oligomers it is moderate and relatively consistent (oP 6 : Φ ) 0.12; oP 8 : Φ ) 0.19; oP 10 : Φ ) 0.19; Figure 2. ORTEP representations (50% ellipsoid probability) of the crystal structures of oP 4 and oP 6 .…”

Section: Synthesismentioning

confidence: 97%

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ortho-Phenylenes: Unusual Conjugated Oligomers with a Surprisingly Long Effective Conjugation Length

et al. 2010

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ortho-Phenylenes represent a fundamental but relatively unexplored class of conjugated molecular architecture. We have developed a robust synthetic approach to monodisperse o-phenylene oligomers which we have demonstrated by synthesizing a homologous series up to the dodecamer. The o-phenylenes exhibit complex conformational behavior but are biased toward a specific 2-fold-symmetric conformation which we believe corresponds to a stacked helix. Surprisingly, the series exhibits long-range delocalization, as measured by bathochromic shifts in UV/vis spectra. Although the overall magnitude of the shifts is modest (but comparable to some other classes of conjugated materials), the effective conjugation length of the series is approximately eight repeat units. The oligomers also exhibit an unusual hypsochromic shift in their fluorescence spectra with increasing length. The origin of these trends is discussed in the context of conformational analysis and DFT calculations of the frontier molecular orbitals for the series.

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Section: Introductionmentioning

confidence: 59%

Section: Synthesismentioning

confidence: 97%

ortho-Phenylenes: Unusual Conjugated Oligomers with a Surprisingly Long Effective Conjugation Length

et al. 2010

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“…The folding of o -phenylenes is of particular interest given their structural simplicity and the possibility that they could be used to better understand the conformational behavior of polyphenylenes in general. However, for 10 years following Simpkins’s original report the field lay largely dormant . This Account focuses on recent investigations of the solution-phase folding of o -phenylenes, focusing mostly on the oP n (X) n series of [ n ]-mers shown in Scheme .…”

Section: Introductionmentioning

confidence: 99%

Folding of ortho-Phenylenes

2016

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In nature, the folding of oligomers and polymers is used to generate complex three-dimensional structures, yielding macromolecules with diverse functions in catalysis, recognition, transport, and charge- and energy-transfer. Over the past 20-30 years, chemists have sought to replicate this strategy by developing new foldamers: oligomers that fold into well-defined secondary structures in solution. A wide array of abiotic foldamers have been developed, ranging from non-natural peptides to aromatics. The ortho-phenylenes represent a recent addition to the family of aromatic foldamers. Despite their structural simplicity (chains of benzenes connected at the ortho positions), it was not until 2010 that systematic studies of o-phenylenes showed that they reliably fold into helices in solution (and in the solid state). This conformational behavior is of fundamental interest: o-Arylene and o-heteroarylene structures are found embedded within many other systems, part of an emerging interest in sterically congested polyphenylenes. Further, o-phenylenes are increasingly straightforward to synthesize because of continuing developments in arene-arene coupling, the Asao-Yamamoto benzannulation, and benzyne polymerization. In this Account, we discuss the folding of o-phenylenes with emphasis on features that make them unique among aromatic foldamers. Interconversion between their different backbone conformers is slow on the NMR time scale around room temperature. The (1)H NMR spectra of oligomers can therefore be deconvoluted to give sets of chemical shifts for different folding states. The chemical shifts are both highly sensitive to conformation and readily predicted using ab initio methods, affording critical information about the conformational distribution. The picture that emerges is that o-phenylenes fold into helices with offset stacking between every third repeat unit. In general, misfolding occurs primarily at the oligomer termini (i.e., "frayed ends"). Because of their structural simplicity, the folding can be described by straightforward models. The overall population can be divided into two enantiomeric pools, with racemization and misfolding as two distinct processes. Examination of substituent effects on folding reveals that the determinant of the relative stability of different conformers is (offset) aromatic stacking interactions parallel to the helical axis. That is, the folding of o-phenylenes is analogous to that of α-helices, with aromatic stacking in place of hydrogen bonding. The folding propensity can be tuned using well-known substituent effects on aromatic stacking, with moderate electron-withdrawing substituents giving nearly perfect folding. The combination of a simple folding mechanism and readily characterized conformational populations makes o-phenylenes attractive structural motifs for incorporation into more-complex architectures, an important part of the next phase of foldamer research.

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“…Commonly, 3 is prepared by dealkylation of 2,3,6,7,10,11-hexamethoxytriphenylene [20–21]. The resulting product is usually a black solid being colorized by chinoide byproducts [20,22] which are not present in our method. However, our method provides easy access to pure 3 which can easily be separated and purified by simple filtration.…”

Section: Resultsmentioning

confidence: 99%

Efficient electroorganic synthesis of 2,3,6,7,10,11-hexahydroxytriphenylene derivatives

Regenbrecht¹,

Waldvogel²

2012

Beilstein J. Org. Chem.

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Summary2,3,6,7,10,11-Hexahydroxytriphenylene of good quality and purity can be obtained via anodic treatment of catechol ketals and subsequent acidic hydrolysis. The electrolysis is conducted in propylene carbonate circumventing toxic and expensive acetonitrile. The protocol is simple to perform and superior to other chemical or electrochemical methods. The key of the method is based on the low solubility of the anodically trimerized product. The shift of potentials is supported by cyclic voltammetry studies.

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Do Catechol Derivatives Electropolymerize?

Abstract: Several recent reports have claimed that catechol and its derivatives undergo electropolymerization when oxidized to form poly(o-phenylene)s. We demonstrate that the products of these electrochemical reactions are likely triphenylene derivatives rather than polymeric materials.

Cited by 21 publications

References 62 publications

ortho-Phenylenes: Unusual Conjugated Oligomers with a Surprisingly Long Effective Conjugation Length

ortho-Phenylenes: Unusual Conjugated Oligomers with a Surprisingly Long Effective Conjugation Length

Folding of ortho-Phenylenes

Efficient electroorganic synthesis of 2,3,6,7,10,11-hexahydroxytriphenylene derivatives

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