\ncalled o-phenylenes have been created by Eisuke Ohta, Takanori Fukushima,
\nTakuzo Aida and colleagues at RIKEN Advanced Science Institute in Wako1.
\nThese oligomers consist of benzene rings that connect to each other at a sharp
\nangle, leading to their helical structure. The team\u2019s oligomers can change shape
\nand become more rigid when subjected to an electrochemical signal (Fig. 1).
\nThey could soon serve as single-molecule machines for application in molecular
\ncomputers.
\n.
\n.
\n
![\"\"](\"https:\/\/azgad.com\/wp-content\/uploads\/\/hi_46521.jpg\" "\\"hi_4652\\"")
<\/a>.<\/p>\n. . The degree of twisting of natural helical structures, such as the DNA double-helix, plays an essential role in many important biological functions. Because of their twisted architecture, artificial helices can facilitate the separation and the synthesis of chiral compounds\u2014asymmetric molecules that cannot be superimposed with their mirror image. New, small spring-like polymer chains, or … <\/p>\n
\n.
\n.
\nFigure 1: <\/strong>o-Phenylene oligomers can be envisaged as springy chairs. When
\noxidized (red), the molecule is contracted and less dynamic than its neutral
\ncounterparts (white).
\n.
\nMany researchers have investigated molecules that alter their features such
\nas color, luminescence and mode of aggregation when exposed to external
\nstimuli. However, the stimuli-induced change in rigidity demonstrated by the
\nRIKEN team is unprecedented and may open the door to new types of molecular
\nswitches.
\nThe researchers synthesized the o-phenylene oligomers using an iterative
\napproach, which allowed them to gradually incorporate electrochemically
\nsensitive units to the oligomer\u2019s backbone.
\n.
\nOhta explains that while trying to generate the longest o-phenylene oligomers
\never synthesized, they noticed that the oligomers possessed highly condensed
\nelectron clouds and exhibited a significant reversible difference in rigidity upon
\nremoval of one electron during oxidation reactions.
\n.
\nThe helical configuration easily causes cyclization\u2014the formation of non-helical
\nstructures\u2014 which makes the synthesis and investigation of open oligomer
\nchains difficult. The researchers overcame this hurdle by replacing hydrogen
\natoms positioned at the extremities of the oligomers with so-called \u2018nitro
\nfunctional groups\u2019. Moreover, the octamer, which consists of eight o-phenylene
\nunits, was essential for extending the helices while preventing the cyclization,
\nproviding long oligomers of up to 48 o-phenylenes.
\n.
\nWhile purifying their products, the researchers discovered that the nitro-bearing
\noctamer underwent a \u2018chiral symmetry-breaking process\u2019, which produced
\ncrystals that contained helices with either a left- or right-handed twist. Furthermore,
\nthe helices rapidly switched handedness in solution. However, during oxidation
\nthese structures contracted, which slowed the switching process between the
\ntwo chiral states, enhancing their lifetime. These long-lived states resemble 0
\nand 1 in binary code, making them attractive for optical memory storage.
\n.
\nThe researchers are currently examining the chemical and physical properties
\nof these oligomers, which remain unexplored to date. \u201cWe want to unveil these
\nproperties now,\u201d says Ohta.
\n.<\/p>\n","protected":false},"excerpt":{"rendered":"