{"id":9512,"date":"2013-02-12T11:41:08","date_gmt":"2013-02-12T11:41:08","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=9512"},"modified":"2013-02-12T11:41:08","modified_gmt":"2013-02-12T11:41:08","slug":"helically-conjugated-molecules-a-follow-up-to-144-annulene","status":"publish","type":"post","link":"https:\/\/www.rzepa.net\/blog\/?p=9512","title":{"rendered":"Helically conjugated molecules. A follow-up to [144]-annulene."},"content":{"rendered":"
\n

An extensive discussion developed regarding my post<\/a> on a fascinating helical [144]-annulene. Topics included the nature of the ring current sustained by the\u00a0\u03c0-electrons and in particular the bond-length alternation around the periphery and whether this should alter if the electron count were to be changed to that of a 4n+2 system (i.e.<\/em> a dication). Whilst the [144]-annulene itself is hypothetical, it emerged that some compounds known as expanded porphyrins have very similar (albeit smaller scale) helical structures. X-ray structures for two such provide useful reality checks on the calculations. Here\u2021\u00a0<\/sup>I include the (3D) coordinates of these two systems so that you can explore for yourself their helicity.<\/p>\n

\"SELQUW.

SELQUW. Click for 3D X-ray structure<\/p><\/div>\n

 <\/p>\n

\"HIYTAL.

HIYTAL. Click for 3D X-ray structure<\/p><\/div>\n

I include below \u0394r<\/sub>meso<\/sup>, being the mean unsigned difference in bond length (\u00c5) at the meso positions of the porphrin <\/a>ring, the calculations being at the 6-311G(d,p) level using the DFT procedure indicated below. The linking number analysis[1]<\/a><\/span> for such systems will be reported elsewhere.[2]<\/a><\/span><\/p>\n\n\n\n\n\n\n
Method<\/td>\nSELQUW<\/td>\nHIYTAL<\/td>\n<\/tr>\n
X-ray<\/td>\n0.048<\/td>\n0.045<\/td>\n<\/tr>\n
B97D\/6-311G(d,p)<\/td>\n0.025<\/a><\/td>\n0.015<\/a><\/td>\n<\/tr>\n
B3LYP\/6-311G(d,p)<\/td>\n0.047<\/a><\/td>\n0.017<\/a><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n

\u2021<\/sup>The WordPress system operated here does not enable 3D coordinates to be inserted into the comment section of a post, only the main body.<\/span><\/p>\n

References<\/h2>\n
  1. S.M. Rappaport, and H.S. Rzepa, \"Intrinsically Chiral Aromaticity. Rules Incorporating Linking Number, Twist, and Writhe for Higher-Twist M\u00f6bius Annulenes\", Journal of the American Chemical Society<\/i>, vol. 130, pp. 7613-7619, 2008. https:\/\/doi.org\/10.1021\/ja710438j<\/a>\n\n<\/li>\n
  2. H.S. Rzepa, \"Lemniscular Hexaphyrins as Examples of Aromatic and Antiaromatic Double-Twist M\u00f6bius Molecules\", Organic Letters<\/i>, vol. 10, pp. 949-952, 2008. https:\/\/doi.org\/10.1021\/ol703129z<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    An extensive discussion developed regarding my post on a fascinating helical [144]-annulene. Topics included the nature of the ring current sustained by the\u00a0\u03c0-electrons and in particular the bond-length alternation around the periphery and whether this should alter if the electron count were to be changed to that of a 4n+2 system (i.e. a dication). Whilst […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[6],"tags":[994,389],"class_list":["post-9512","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","tag-helical-annulenes","tag-x-ray"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p1gPyz-2tq","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/9512","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=9512"}],"version-history":[{"count":0,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/9512\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=9512"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=9512"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=9512"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}