ortho-Tetraaryls as helical building blocks: a study of structure, theory, electrochemistry, and optical properties

Almutairi, Adah; Tham, Fook S.; Marsella, Michael J.

doi:10.1016/j.tet.2004.06.077

Cited by 13 publications

(10 citation statements)

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“…[ 40 ] Mahato and coworkers [ 41 ] synthesized a tetramer of indole, 3, whose X-ray structure shows a helical conformation. Marsella and coworkers [42,43,44] synthesized sexithiophene, 4 (X = H, Cl, or Br), and its X-ray structure confirmed a predicted helical conformation. This helical structure exhibits redox-induced conformational changes.…”

Section: Resultsmentioning

confidence: 93%

Helical Oligoenes: Conformations, Bond Alternation, and Competing Through‐Bond and Through‐Space Transmission

Tsuji

Hoffmann

2016

Chemistry A European J

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There is a consensus that long-range electron transfer/transport occurs by a through-bond rather than through-space mechanism. In helical all-Z, all-s-cis oligoenes, one can set up an interesting competition in the medium-separation regime between a closer (in distance) through-space path and a more distant through-bond one. Although such oligoene conformations/isomers are unstable (by around 4 kcal mol(-1) per double bond relative to all-E, all-s-trans isomers), recent synthetic efforts on truncated helicenes and oligothiophenes have provided related molecules. On the way to transmission calculations with electrodes attached to the termini of helical oligoenes, we uncover an interesting conformational ambiguity in all-Z, all-s-cis oligoenes, the existence of a broad conformational minimum for helical compression, with hints of end-to-end frontier-orbital-caused stabilization. There is relationship between helical oligoene structures and the corresponding substructure of a helicene, but there are also significant differences in the number of olefin subunits per helix turn. In Hückel transport calculations, the role of TB or TS mechanisms is obscured to an extent by variations in bond alternation and dihedral angle along the oligomer chain. However, the operation of a dominant through bond mechanism emerges clearly in local transmission plots. In moving the electrodes to carbon position related by quantum interference, it is possible to uncover a through space mechanism.

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Section: Resultsmentioning

confidence: 93%

Helical Oligoenes: Conformations, Bond Alternation, and Competing Through‐Bond and Through‐Space Transmission

Tsuji

Hoffmann

2016

Chemistry A European J

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“…Our molecular dynamic simulations (shown on left in Fig. 4) explain this short effective conjugation length to be due to a spiraling backbone [12]. Figure 4 also reports the real-time EMA response to an 80-µm-thick film of poly(2a), measured according to our previously reported cyclic-voltammetry/laser-micrometry analytical technique [15].…”

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confidence: 86%

“…The rationale for the inclusion of terminal phenyl rings is to limit the number of reactive α-thienyl sites to two. This mandates that electrochemical polymerization would occur specifically through the bithiophene unit [12]. Figure 1 shows the four derivatives reported herein, compounds 2a and 3a bear no α-thienyl substituents, compounds 2b and 3b have phenyl substituents at both α-thienyl positions, and compound 3c has chlorines at the two α-theinyl positions as well as a perfluoropyridyl in place of the phenyl groups in 3a.…”

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confidence: 93%

Molecular springs and muscles: Progress toward augmented electromechanical actuation

Almutairi

Yoon

Tham

et al. 2006

Pure and Applied Chemistry

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The application of 3,3'-diphenyl-2,2'-bithiophene as a helical scaffold capable of electrochemical polymerization to yield the corresponding polythiophene is reported. One unique feature of this monomer is its theoretically predicted (DFT) ability to mimic redoxstimulated contraction and expansion. This ability, coupled with traditional electromechanical actuation properties of bulk, redox-active conjugated polymers (CPs), yields a polymeric "molecular muscle" capable of both contraction and expansion.Keywords: electromechanical actuation; polythiophene; helicity; diphenylbithiophene; molecular muscle.The generation of motion, referred to also as actuation, results from free-energy transduction caused by a chemical, electronic, or electromagnetic stimulus [1]. An elegant actuating system developed by Nature is skeletal muscle. Muscles are composed of 1D filaments, bound together by van der Waals (VDW) interactions into bundles of fibers. The filaments, containing copper(II/I) centers and phosphate ligands, are set into motion by chemical signal, which initiates a reversible actuation (chemomechanical actuation).Actuators composed of conjugated polymers (CPs) serve as non-natural surrogates of biological muscle. The systems act as electromechanical actuators (EMAs, a.k.a. "molecular muscles") via redoxinduced counterion adsorption and expulsion. For example, oxidation of a bulk CP sample requires an influx of charge-balancing counterions and solvating species. The intercalated species have a defined volume, which results in the oxidized CP to have a volume greater than the neutral CP. This reversible volume change can be utilized to perform work. Note that the mechanism invoked by traditional CP-EMAs relies on ion and solvent intercalation, thus is not intrinsic to CP strands [2]. Often, this mechanism leads to degradation of the life and rate of faradaic conducting polymer actuators [2]. Recent efforts in the field of molecular actuators have focused on investigating and expanding upon the properties and behavior of electrolytes [3].A different approach would be to augment the actuation resulting from redox-induced ion-intercalation (bulk actuation) with CPs that are capable of intrinsic actuation [4][5][6][7][8][9][10]. Specifically, if each repeat unit of a polymer was capable of redox-induced conformational change that results in a change in volume and/or length, then intrinsic actuation could act to augment bulk actuation. Preferably, intrinsic actuation would be active in the "light-doping regime" of the polymer, where "light doping" implies that the polymer is oxidized to a state less than that corresponding to the observed peak anodic current (I p,a , as determined from cyclic voltammetry). This strategy may help remedy degradation problems resulting from high CP oxidation states ("heavy doping").

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“…o -Tetraaryls are advantageous building blocks for the construction of specific polyaromatic hydrocarbons (PAHs), which were now well-established as functional materials ( A and B , Figure ) or catalyst ligands ( C , Figure ). Furthermore, o- oligoaryls were identified to adopt a helical conformation, leading to applications as three-dimensional scaffolds in the study of steric interactions along the rigid backbone . With regard to the preparation of o- oligoaryls, mono-Suzuki–Miyaura couplings between the biphenyl derivatives are well recorded (monocoupling, Figure ).…”

Section: Introductionmentioning

confidence: 99%

Palladium-Catalyzed Double-Suzuki–Miyaura Reactions Using Cyclic Dibenziodoniums: Synthesis of o-Tetraaryls

2015

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ortho-Tetraaryls as helical building blocks: a study of structure, theory, electrochemistry, and optical properties

Cited by 13 publications

References 13 publications

Helical Oligoenes: Conformations, Bond Alternation, and Competing Through‐Bond and Through‐Space Transmission

Helical Oligoenes: Conformations, Bond Alternation, and Competing Through‐Bond and Through‐Space Transmission

Molecular springs and muscles: Progress toward augmented electromechanical actuation

Palladium-Catalyzed Double-Suzuki–Miyaura Reactions Using Cyclic Dibenziodoniums: Synthesis of o-Tetraaryls

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