{"id":10910,"date":"2016-12-16T07:01:40","date_gmt":"2016-12-16T07:01:40","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=10910"},"modified":"2016-12-16T07:01:40","modified_gmt":"2016-12-16T07:01:40","slug":"first-experimental-evidence-3d-aromaticity-stacked-antiaromatic-compounds","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/first-experimental-evidence-3d-aromaticity-stacked-antiaromatic-compounds\/","title":{"rendered":"First experimental evidence of 3D aromaticity in stacked antiaromatic compounds"},"content":{"rendered":"

International collaboration led by Nagoya University uses two-dimensional antiaromatic materials to realize three-dimensional aromatic structures.<\/strong><\/em><\/span><\/p>\n

\"Antiaromatic
Antiaromatic planar norcorrole molecules form close face-to-face stacked structures with increased aromaticity. This behavior is quite different from that of planar aromatic molecules. This result is the first experimental proof for the theoretical prediction that the stacking of antiaromatic molecules may result in the formation of materials with three-dimensional aromaticity.
Credit : Nagoya University<\/figcaption><\/figure>\n

Nagoya, Japan \u2013 Aromatic molecules consist of planar carbon-based rings with alternating single and double (\u03c0) bonds. These molecules contain 4n+2 (n = 0, 1, 2 \u2026) \u03c0 electrons\u2014\u03c0 electrons are those involved in \u03c0 bonds\u2014which results in high stability because the \u03c0 electrons delocalize over the ring structure. Aromatic molecules can interact through offset \u03c0-\u03c0 stacking, and the overlap of \u03c0 orbitals in aromatic structures with \u03c0-\u03c0 stacking can facilitate electron conduction, making such materials attractive for use in electronics. The overlap between \u03c0 orbitals would be increased if \u03c0-\u03c0 stacking was face-to-face rather than offset. However, face-to-face stacking is energetically unfavorable in aromatic molecules because of the repulsion of \u03c0 electrons.<\/span><\/p>\n

Theoretical studies have indicated that face-to-face interactions between molecules may be achieved using antiaromatic materials. Antiaromatic molecules contain 4n (n = 1, 2 \u2026) \u03c0 electrons, which makes them highly unstable. It has been postulated that the two-dimensional stacking of antiaromatic materials may result in the formation of materials with three-dimensional aromaticity. However, this had not been verified experimentally as antiaromatic materials are difficult to synthesize because of their instability.<\/span><\/p>\n

Recently, an international collaboration led by researchers at Nagoya University achieved a breakthrough in two-dimensional stacking of antiaromatic materials. They synthesized nickel complexes of antiaromatic planar norcorrole macrocycles. The study was reported in Nature Communications.<\/span><\/p>\n

\u201cWe synthesized stable antiaromatic nickel norcorroles and then investigated their interactions,\u201d first author Ryo Nozawa says. X-ray diffraction analysis showed that the norcorrole complex stacked to form a \u201ctriple-decker\u201d structure with the norcorrole planes much closer together than observed for typical \u03c0-\u03c0 stacking interactions. The triple-decker structure displayed aromatic characteristics, unlike its norcorrole subunits.<\/span><\/p>\n

The researchers then fabricated a molecule containing two antiaromatic norcorrole units linked by a flexible bridge.<\/span><\/p>\n

\u201cOur characterization results indicate that the two norcorrole units assume face-to-face interactions to form a molecule with higher aromaticity than that of the norcorrole subunit,\u201d coauthor Hiroshi Shinokubo explains. \u201cThat is, there is strong three-dimensional electronic communication between the norcorrole subunits.\u201d<\/span><\/p>\n

The stacking of antiaromatic units gave closer interactions than that achieved when stacking aromatic units together, corroborating theoretical predictions. The resulting materials had extremely close \u03c0-conjugated systems, which should result in large intermolecular orbital interactions. As a result, these materials are interesting for application in optoelectronics.<\/span><\/p>\n

The researchers also found that the stacked antiaromatic materials displayed nonlinear optical properties that were regulated by the formation of supramolecular structures. A material has nonlinear optical properties when it does not respond linearly to the electric field of light. Such materials are attractive for use in nanofabrication and photodynamic therapy, suggesting possible future applications of norcorrole-based compounds.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Aromatic molecules consist of planar carbon-based rings with alternating single and double (\u03c0) bonds. These molecules contain 4n+2 (n = 0, 1, 2 \u2026) \u03c0 electrons\u2014\u03c0 electrons are those involved in \u03c0 bonds\u2014which results in high stability because the \u03c0 electrons delocalize over the ring structure. Aromatic molecules can interact through offset \u03c0-\u03c0 stacking, and the overlap of \u03c0 orbitals in aromatic structures with \u03c0-\u03c0 stacking can facilitate electron conduction, making such materials attractive for use in electronics.<\/p>\n","protected":false},"author":6,"featured_media":10911,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-10910","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",960,720,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102-300x225.jpg",300,225,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102-768x576.jpg",750,563,true],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",750,563,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",960,720,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",960,720,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",960,720,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",760,570,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",600,450,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",600,450,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",653,490,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",480,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",87,65,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",640,480,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",96,72,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/12\/4102.jpg",150,113,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/10910","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=10910"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/10910\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/10911"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=10910"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=10910"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=10910"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}