5941-49-1Relevant articles and documents
A Peierls Transition in Long Polymethine Molecular Wires: Evolution of Molecular Geometry and Single-Molecule Conductance
Xu, Wenjun,Leary, Edmund,Sangtarash, Sara,Jirasek, Michael,González, M. Teresa,Christensen, Kirsten E.,Abellán Vicente, Lydia,Agra?t, Nicolás,Higgins, Simon J.,Nichols, Richard J.,Lambert, Colin J.,Anderson, Harry L.
supporting information, p. 20472 - 20481 (2021/12/09)
Molecules capable of mediating charge transport over several nanometers with minimal decay in conductance have fundamental and technological implications. Polymethine cyanine dyes are fascinating molecular wires because up to a critical length, they have no bond-length alternation (BLA) and their electronic structure resembles a one-dimensional free-electron gas. Beyond this threshold, they undergo a symmetry-breaking Peierls transition, which increases the HOMO-LUMO gap. We have investigated cationic cyanines with central polymethine chains of 5-13 carbon atoms (Cy3+-Cy11+). The absorption spectra and crystal structures show that symmetry breaking is sensitive to the polarity of the medium and the size of the counterion. X-ray crystallography reveals that Cy9·PF6 and Cy11·B(C6F5)4 are Peierls distorted, with high BLA at one end of the π-system, away from the partially delocalized positive charge. This pattern of BLA distribution resembles that of solitons in polyacetylene. The single-molecule conductance is essentially independent of molecular length for the polymethine salts of Cy3+-Cy11+ with the large B(C6F5)4- counterion, but with the PF6- counterion, the conductance decreases for the longer molecules, Cy7+-Cy11+, because this smaller anion polarizes the π-system, inducing a symmetry-breaking transition. At higher bias (0.9 V), the conductance of the shorter chains, Cy3+-Cy7+, increases with length (negative attenuation factor, β = -1.6 nm-1), but the conductance still drops in Cy9+ and Cy11+ with the small polarizing PF6- counteranion.
Controlling Asymmetric Remote and Cascade 1,3-Dipolar Cycloaddition Reactions by Organocatalysis
Poulsen, Pernille H.,Vergura, Stefania,Monleón, Alicia,J?rgensen, Danny Kaare Bech,J?rgensen, Karl Anker
supporting information, p. 6412 - 6415 (2016/06/09)
The regio- and stereoselective control of cycloaddition reactions to polyconjugated systems has been demonstrated by applying asymmetric organocatalysis. Reaction of 2,4-dienals with nitrones allows for a highly regio- and stereoselective 1,3-dipolar cycl
Process for the preparation of 2,4,6-octatriene-1-oic acid and 2,4,6-octatriene-1-ol
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Page/Page column 4, (2010/11/03)
The present invention concerns a process for synthesis of 2,4,6-octatriene-1-oic acid and 2,4,6-octatriene-1-ol, which comprises the following stages: a) reaction between 2,4-trans-hexadienal and triethyl phosphonoacetate to give ethyl 2,4,6-trans-octatrienoate; b) alkaline hydrolysis of ethyl 2,4,6-trans-octatrienoate to give the corresponding alkaline salt; c) acidification of said salt to give 2,4,6-trans-octatrienoic acid, which can be separated or can undergo the following further stages: d) reaction of the 2,4,6-trans-octatrienoic acid with ethyl chloroformiate to give the mixed anhydride formed by 2,4,6-trans-octatrienoic acid and ethyl carbonic acid; e) reduction of said mixed anhydride with sodium borohydride to give 2,4,6-transoctatrienol; and optionally a purification stage of the end product.
