{"id":5615,"date":"2011-11-25T12:24:11","date_gmt":"2011-11-25T12:24:11","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=5615"},"modified":"2011-11-25T12:24:11","modified_gmt":"2011-11-25T12:24:11","slug":"the-chemistry-behind-a-molecular-motor-the-four-wheels","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5615","title":{"rendered":"The chemistry behind a molecular motor. The four wheels?"},"content":{"rendered":"
\n

In the previous post<\/a>, I wrote about the processes that might<\/em> be involved in a molecular wheel rotating. A nano car has four wheels, and surely the most amazing thing is how the wheels manage to move in synchrony. This is one hell of a tough problem, and I do not attempt an answer here, but simply record an odd observation.<\/p>\n

\"\"<\/a><\/p>\n

To rotate the wheel, the axle has to rotate, and this can be made to happen by electronically exciting it to decouple the two \u03c0-electrons. To study the excited state computationally requires a technique known as CASSCF, and the molecule above is far too big for such a method. But a crude approximation would be to decouple the spins of the two \u03c0-electrons by computing the triplet state. One can in fact decouple progressively by computing respectively the triplet, quintet, septet and nonet states. To ensure equality, these calculations were all started from the optimised singlet geometry, and allowed to evolve. One might imagine for example that the triplet state might end up delocalized over the entire molecule, weakening all four axles at the same time, although of course for this to happen, the nitrogens would have to participate.<\/p>\n

The animation below shows the progress of the septet state. Watch the four axles individually, and notice how from the very start, three of them start to rotate, whilst the fourth (bottom left) stays rock steady!<\/p>\n

\"\"

Septet spin state for the nano car. Click for 3D of final geometry.<\/p><\/div>The really interesting one is the quintet state, where the green and magenta axles rotate, and the red and blue ones do not.<\/p>\n

\"\"

Quintet state. Click for 3D.<\/p><\/div>The triplet state reserves rotation for just one (red) axle, but the connecting chassis of the car also buckles.<\/p>\n

\"\"

Triplet state. Click for 3D.<\/p><\/div>The last state, the nonet, shows all four wheels rotated.<\/p>\n

\"\"

Nonet state. Click for 3D.<\/p><\/div>The relative energies of the five states are\u00a00.0, 32.6<\/a>, 60.0<\/a>, 107.7<\/a> and 125.3 <\/a>kcal\/mol. It seems there is not much electronic communication between the axles of the four wheels, possibly because to do so, they would have to disrupt the aromaticity of the intervening “Clar” benzo group adjacent to each axle.<\/p>\n

Which makes the ability of this nano car to coordinate the motions of its wheels when travelling even more interesting!<\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

In the previous post, I wrote about the processes that might be involved in a molecular wheel rotating. A nano car has four wheels, and surely the most amazing thing is how the wheels manage to move in synchrony. This is one hell of a tough problem, and I do not attempt an answer here, […]<\/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,"activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":5,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"","footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[4],"tags":[152,771],"ppma_author":[2661],"class_list":["post-5615","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","tag-animation","tag-nano-car"],"yoast_head":"\nThe chemistry behind a molecular motor. 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It has now been detected in the atmosphere of Titan, one of Saturn's moons and joins benzene, another aromatic molecule together with the protonated version of cyclopropenylidene, C3H3+ also\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":10498,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=10498","url_meta":{"origin":5615,"position":3},"title":"Au and Pt \u03c0-complexes of cyclobutadiene.","author":"Henry Rzepa","date":"May 15, 2013","format":false,"excerpt":"In the preceding post, I introduced Dewar's\u00a0\u03c0-complex theory for alkene-metal compounds, outlining the molecular orbital analysis he presented, in which the filled \u03c0-MO of the alkene donates into a Ag+\u00a0empty metal orbital and back-donation occurs from a filled metal orbital into the alkene \u03c0* MO. Here I play a little\u2026","rel":"","context":"In "Hypervalency"","block_context":{"text":"Hypervalency","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=7"},"img":{"alt_text":"Pt-cbd","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/05\/Pt-cbd.jpeg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":10448,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=10448","url_meta":{"origin":5615,"position":4},"title":"The \u03c0-complex theory of metal-alkene compounds.","author":"Henry Rzepa","date":"May 13, 2013","format":false,"excerpt":"The period 1951--1954 was a golden one for structural chemistry; proteins, DNA, Ferrocene (1952) and the one I discuss here, a bonding model for Zeise's salt (3). In\u00a0\"A review of \u03c0 Complex Theory\",\u00a0 Bull. Soc. Chim. Fr., 1951, 1 8 , C79 (it is not online) M. J. S.\u00a0Dewar\u00a0sets out\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":3462,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=3462","url_meta":{"origin":5615,"position":5},"title":"Shorter is higher: the strange case of diberyllium.","author":"Henry Rzepa","date":"January 21, 2011","format":false,"excerpt":"Much of chemistry is about bonds, but sometimes it can also be about anti-bonds. It is also true that the simplest of molecules can have quite subtle properties. Thus most undergraduate courses in chemistry deal with how to describe the bonding in the diatomics of the first row of the\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/01\/Be2a.jpg?resize=350%2C200","width":350,"height":200},"classes":[]}],"jetpack_likes_enabled":false,"authors":[{"term_id":2661,"user_id":1,"is_guest":0,"slug":"admin","display_name":"Henry Rzepa","avatar_url":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","0":null,"1":"","2":"","3":"","4":"","5":"","6":"","7":"","8":""}],"_links":{"self":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/5615","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=5615"}],"version-history":[{"count":0,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/5615\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5615"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5615"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5615"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=5615"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}