{"id":18532,"date":"2017-06-18T18:38:50","date_gmt":"2017-06-18T17:38:50","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=18532"},"modified":"2017-06-19T06:41:29","modified_gmt":"2017-06-19T05:41:29","slug":"chemistry-rich-diagrams-do-crystal-structures-carry-spin-information-iron-di-imine-complexes","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18532","title":{"rendered":"Chemistry rich diagrams: do crystal structures carry spin information? Iron-di-imine complexes."},"content":{"rendered":"<div class=\"kcite-section\" kcite-section-id=\"18532\">\n<p>The iron complex shown below forms the basis for many catalysts.<span id=\"cite_ITEM-18532-0\" name=\"citation\"><a href=\"#ITEM-18532-0\">[1]<\/a><\/span> With iron, the catalytic behaviour very much depends on the spin-state of the molecule, which for the below can be either high (hextet) or medium (quartet) spin, with a possibility also of a low spin (doublet) state. Here I explore whether structural information in crystal structures can reflect such spin states.<\/p>\n<p><a href=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/Fe-page001.svg\"><img decoding=\"async\" class=\"aligncenter size-large wp-image-18534\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/Fe-page001.svg\" alt=\"\" width=\"200\" \/><\/a><\/p>\n<p>We studied this a few years back and the talk I gave on the topic included some of our first statistical explorations of the CSD (Cambridge structure database). Here I update those searches, using the search query (DOI: <a href=\"https:\/\/doi.org\/10.14469\/hpc\/2675\">10.14469\/hpc\/2675<\/a>) shown below. The di-imine ligand contains only 3-coordinate atoms, whilst the iron is 5-coordinate. The angles subtended at the Fe and group X=NM (any non-metal atom) are as defined below.<\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-full wp-image-18535\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/Fe.jpg\" alt=\"\" width=\"400\" srcset=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/Fe.jpg 569w, https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/Fe-232x300.jpg 232w\" sizes=\"(max-width: 569px) 100vw, 569px\" \/><\/p>\n<p>The resulting scatterplot is shown below and contains a rich variety of phenomena.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-large wp-image-18536\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/188-1024x743.jpg\" alt=\"\" width=\"450\" height=\"327\" srcset=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/188-1024x743.jpg 1024w, https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/188-300x218.jpg 300w, https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/188-768x557.jpg 768w, https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/188.jpg 1326w\" sizes=\"auto, (max-width: 450px) 100vw, 450px\" \/><\/p>\n<ol>\n<li>In the bond length region of 1.85-1.95\u00c5 one sees three clusters, one arranged on the diagonal indicating both N-Fe lengths are the same and two off the diagonal which indicates one length is ~0.1\u00c5 longer than the other.\n<ul>\n<li>To explain this, one needs to know that 5-coordinate Fe has a trigonal bipyramidal shape in which one X=NM group subtends an (anti-periplanar) \u00a0angle of ~180\u00b0 at Fe with one of the ring nitrogens and the other two X=NM groups each subtend an angle of &lt;120\u00b0 with the other ring nitrogen. The result is that if the group X has the appropriate (electron withdrawing) properties, the two N-Fe bond lengths are no longer equal. If group X is more passive, the two N-Fe bond lengths may remain more equal.<br \/>\n <img decoding=\"async\" class=\"aligncenter size-large wp-image-18539\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/186-1024x894.jpg\" alt=\"\" width=\"400\" \/><\/li>\n<\/ul>\n<\/li>\n<li>A second cluster occurs at ~2.00-2.1\u00c5, mostly along the diagonal but with hints of smaller off-diagonal clusters.<\/li>\n<li>A third feature occurs at ~2.1-2.3\u00c5, where now the off-diagonal clusters contain more examples than are on the diagonal itself.<\/li>\n<\/ol>\n<p>Clearly, there is more going on here than can be explained simply by the orientation of X=NM with respect to the Fe-N bond axis. That something is the spin-multiplicity of the molecule. With the Fe complex shown above, this can be one of doublet (one unpaired electron), quartet (three unpaired electrons) or hextet (five unpaired electrons). To gain insight into how this affects the bond lengths, some calculations are needed, using X=Cl, R=H. Here they are done at the TPSSH\/Def2-TZVPP level. In fact it is well-known<span id=\"cite_ITEM-18532-1\" name=\"citation\"><a href=\"#ITEM-18532-1\">[2]<\/a><\/span> that the energy separations of low\/medium\/high spin Fe complexes are highly sensitive to the functional, but TPSSH seems to be amongst the best.<sup>\u2021<\/sup> This shows that the energy ordering of the three states using this particular method is hextet (0.0, DOI: <a href=\"https:\/\/doi.org\/10.14469\/hpc\/2676\">10.14469\/hpc\/2676<\/a>) &lt; quartet (10.5, DOI: <a href=\"https:\/\/doi.org\/10.14469\/hpc\/2677\">10.14469\/hpc\/2677<\/a>) &lt; doublet (13.2 kcal\/mol, DOI: <a href=\"https:\/\/doi.org\/10.14469\/hpc\/2678\">10.14469\/hpc\/2678<\/a>), with the bond lengths shown below (for X=Cl).<img decoding=\"async\" class=\"aligncenter size-large wp-image-18541\" src=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/Fe1-305x1024.jpg\" alt=\"\" width=\"150\" srcset=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/Fe1-305x1024.jpg 305w, https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/Fe1-89x300.jpg 89w, https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/Fe1.jpg 503w\" sizes=\"(max-width: 305px) 100vw, 305px\" \/><\/p>\n<p>We might make tentative hypotheses based on these values:<\/p>\n<ol>\n<li>The off-diagonal bottom left clusters (1 in list above) might arise from doublet states.<\/li>\n<li>The off-diagonal top right clusters (3 in list above) might arise from sextet states.<\/li>\n<li>The cluster (2 in list above) might be quartet states for which X is not sufficiently electronegative to induce bond length discriminations.<\/li>\n<li>It is worth noting that the energy span between the three states for the above molecule is only ~13 kcal\/mol, which is small enough to be altered by substituents.<\/li>\n<\/ol>\n<p>Testing these hypotheses requires knowledge of the spin state of all the entries in any cluster. This information is unfortunately not carried by the CSD, which has relatively little information over and above structural data. Each entry would have to be individually inspected. Indeed the spin state of many of these complexes may not even be known. Nevertheless, it would be great to repeat the graphs shown above as a function of known spin state so that the (again I repeat tentative) hypotheses might be confirmed or refuted.<\/p>\n<hr \/>\n<p><sup>\u2021<\/sup>This article evaluates a whole host of functionals against <i>e.g.<\/i> the spin-state energy separations of the Fe<sup>2+<\/sup> ion. As it happens, TPSSH was <b>not<\/b> one that was evaluated, but in fact it gives more or less the best match to experiment. Thus E<sub>singlet<\/sub>-E<sub>quintet<\/sub> obs = 85.6 kcal\/mol, calc 92.4; E<sub>triplet<\/sub>-E<sub>quintet<\/sub> obs 56.1, calc 59.5 kcal\/mol. A hypothesis therefore is that the TPSSH functional is a reasonable one to go exploring such high-spin species.<\/p>\n<h2>References<\/h2>\n    <ol class=\"kcite-bibliography csl-bib-body\"><li id=\"ITEM-18532-0\">M.P. Shaver, L.E.N. Allan, H.S. Rzepa, and V.C. Gibson, \"Correlation of Metal Spin State with Catalytic Reactivity: Polymerizations Mediated by \u03b1\u2010Diimine\u2013Iron Complexes\", <i>Angewandte Chemie International Edition<\/i>, vol. 45, pp. 1241-1244, 2006. <a href=\"https:\/\/doi.org\/10.1002\/anie.200502985\">https:\/\/doi.org\/10.1002\/anie.200502985<\/a>\n\n<\/li>\n<li id=\"ITEM-18532-1\">P. Verma, Z. Varga, J.E.M.N. Klein, C.J. Cramer, L. Que, and D.G. Truhlar, \"Assessment of electronic structure methods for the determination of the ground spin states of Fe(&lt;scp&gt;ii&lt;\/scp&gt;), Fe(&lt;scp&gt;iii&lt;\/scp&gt;) and Fe(&lt;scp&gt;iv&lt;\/scp&gt;) complexes\", <i>Physical Chemistry Chemical Physics<\/i>, vol. 19, pp. 13049-13069, 2017. <a href=\"https:\/\/doi.org\/10.1039\/c7cp01263b\">https:\/\/doi.org\/10.1039\/c7cp01263b<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> <!-- kcite-section 18532 -->","protected":false},"excerpt":{"rendered":"<p>The iron complex shown below forms the basis for many catalysts. With iron, the catalytic behaviour very much depends on the spin-state of the molecule, which for the below can be either high (hextet) or medium (quartet) spin, with a possibility also of a low spin (doublet) state. Here I explore whether structural information in [&hellip;]<\/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":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[1745],"tags":[1138,2220,1395,24,2226,2224,2223,2219,2221,1848,2225,2222],"ppma_author":[2661],"class_list":["post-18532","post","type-post","status-publish","format-standard","hentry","category-crystal_structure_mining","tag-catalysis","tag-catalysts","tag-chemistry","tag-energy","tag-energy-separations","tag-energy-span","tag-fe-complex","tag-homogeneous-catalysis","tag-kumada-coupling","tag-organometallic-chemistry","tag-spin-state-energy-separations","tag-synergistic-catalysis"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.5 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Chemistry rich diagrams: do crystal structures carry spin information? Iron-di-imine complexes. - Henry Rzepa&#039;s Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18532\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Chemistry rich diagrams: do crystal structures carry spin information? Iron-di-imine complexes. - Henry Rzepa&#039;s Blog\" \/>\n<meta property=\"og:description\" content=\"The iron complex shown below forms the basis for many catalysts. With iron, the catalytic behaviour very much depends on the spin-state of the molecule, which for the below can be either high (hextet) or medium (quartet) spin, with a possibility also of a low spin (doublet) state. Here I explore whether structural information in [&hellip;]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18532\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa&#039;s Blog\" \/>\n<meta property=\"article:published_time\" content=\"2017-06-18T17:38:50+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2017-06-19T05:41:29+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/Fe-page001.svg\" \/>\n<meta name=\"author\" content=\"Henry Rzepa\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Henry Rzepa\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"4 minutes\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Chemistry rich diagrams: do crystal structures carry spin information? Iron-di-imine complexes. - Henry Rzepa&#039;s Blog","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18532","og_locale":"en_GB","og_type":"article","og_title":"Chemistry rich diagrams: do crystal structures carry spin information? Iron-di-imine complexes. - Henry Rzepa&#039;s Blog","og_description":"The iron complex shown below forms the basis for many catalysts. With iron, the catalytic behaviour very much depends on the spin-state of the molecule, which for the below can be either high (hextet) or medium (quartet) spin, with a possibility also of a low spin (doublet) state. Here I explore whether structural information in [&hellip;]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18532","og_site_name":"Henry Rzepa&#039;s Blog","article_published_time":"2017-06-18T17:38:50+00:00","article_modified_time":"2017-06-19T05:41:29+00:00","og_image":[{"url":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/Fe-page001.svg","type":"","width":"","height":""}],"author":"Henry Rzepa","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Henry Rzepa","Estimated reading time":"4 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18532#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18532"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"Chemistry rich diagrams: do crystal structures carry spin information? Iron-di-imine complexes.","datePublished":"2017-06-18T17:38:50+00:00","dateModified":"2017-06-19T05:41:29+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18532"},"wordCount":725,"commentCount":1,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18532#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/06\/Fe-page001.svg","keywords":["catalysis","Catalysts","Chemistry","energy","energy separations","energy span","Fe complex","Homogeneous catalysis","Kumada coupling","Organometallic chemistry","spin-state energy separations","Synergistic catalysis"],"articleSection":["crystal_structure_mining"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18532#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18532","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18532","name":"Chemistry rich diagrams: do crystal structures carry spin information? 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Iron-di-imine complexes."}]},{"@type":"WebSite","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#website","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/","name":"Henry Rzepa&#039;s Blog","description":"Chemistry with a twist","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-GB"},{"@type":"Person","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281","name":"Henry Rzepa","image":{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g370be3a7397865e4fd161aefeb0a5a85","url":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","caption":"Henry Rzepa"},"description":"Henry Rzepa is Emeritus Professor of Computational Chemistry at Imperial College London.","sameAs":["https:\/\/orcid.org\/0000-0002-8635-8390"],"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?author=1"}]}},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/pDef7-4OU","jetpack-related-posts":[{"id":4814,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4814","url_meta":{"origin":18532,"position":0},"title":"Mindless chemistry or creative science?","author":"Henry Rzepa","date":"September 3, 2011","format":false,"excerpt":"The (hopefully tongue-in-cheek) title Mindless chemistry was given to an article reporting an automated stochastic search procedure for locating all possible minima with a given composition using high-level quantum mechanical calculations. \"Many new structures, often with nonintuitive geometries, were found\". Well, another approach is to follow unexpected hunches. One such\u2026","rel":"","context":"In &quot;Interesting chemistry&quot;","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.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/09\/fe2.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":26199,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=26199","url_meta":{"origin":18532,"position":1},"title":"Blue blood.","author":"Henry Rzepa","date":"August 7, 2023","format":false,"excerpt":"Respiratory pigments are metalloproteins that transport O2, the best known being the bright red\/crimson coloured hemoglobin in human blood. The colour derives from Fe2+ at the core of a tetraporphyrin ring. But less well known is blue blood, and here the colour derives from an oxyhemocyanin unit based on Cu1+\u2026","rel":"","context":"In &quot;crystal_structure_mining&quot;","block_context":{"text":"crystal_structure_mining","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1745"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/08\/Screenshot57.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/08\/Screenshot57.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/08\/Screenshot57.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/08\/Screenshot57.jpg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/08\/Screenshot57.jpg?resize=1050%2C600&ssl=1 3x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/08\/Screenshot57.jpg?resize=1400%2C800&ssl=1 4x"},"classes":[]},{"id":8776,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8776","url_meta":{"origin":18532,"position":2},"title":"How to tame an oxidant: the mysteries of &#8220;tpap&#8221; (tetra-n-propylammonium perruthenate).","author":"Henry Rzepa","date":"December 24, 2012","format":false,"excerpt":"tpap, as it is affectionately known, is a ruthenium-based oxidant of primary alcohols to aldehydes discovered by Griffith and Ley. Whereas ruthenium tetroxide (RuO4) is a voracious oxidant, its radical anion countered by a tetra-propylammonium cation is considered a more moderate animal. In this post, I want to try to\u2026","rel":"","context":"In &quot;Interesting chemistry&quot;","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"ts2-triplet-spin","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/12\/ts2-triplet-spin.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":12978,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=12978","url_meta":{"origin":18532,"position":3},"title":"WATOC2014 Conference report. Emergent themes.","author":"Henry Rzepa","date":"October 9, 2014","format":false,"excerpt":"This second report highlights two \"themes\", or common ideas that seem to emerge spontaneously from diversely different talks. Most conferences do have them. The first is \"embedding\", which in this context means treating different parts of a probably complex molecular system at different levels of theory. Thus Emily Carter in\u2026","rel":"","context":"In &quot;Interesting chemistry&quot;","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":8588,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8588","url_meta":{"origin":18532,"position":4},"title":"Why is the Sharpless epoxidation enantioselective? Part 1: a simple model.","author":"Henry Rzepa","date":"December 9, 2012","format":false,"excerpt":"Sharpless epoxidation converts a prochiral allylic alcohol into the corresponding chiral epoxide with > 90% enantiomeric excess,. Here is the first step in trying to explain how this magic is achieved. The scheme above shows how (achiral) prop-2-enol is converted using the asymmetric catalyst\u00a0(R,R)-diethyl tartrate \u00a0and t-butyl hydroperoxide as oxidant\u2026","rel":"","context":"In &quot;Interesting chemistry&quot;","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.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/12\/sharpless.gif?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":2594,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=2594","url_meta":{"origin":18532,"position":5},"title":"Rate enhancement of the Diels-Alder reaction inside a cavity","author":"Henry Rzepa","date":"October 30, 2010","format":false,"excerpt":"Reactions in cavities can adopt quite different characteristics from those in solvents. Thus first example of the catalysis of the Diels-Alder reaction inside an organic scaffold was reported by Endo, Koike, Sawaki, Hayashida, Masuda, and Aoyama, where the reaction shown below is speeded up very greatly in the presence of\u2026","rel":"","context":"In &quot;Interesting chemistry&quot;","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\/2010\/09\/res_scheme.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\/18532","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=18532"}],"version-history":[{"count":14,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/18532\/revisions"}],"predecessor-version":[{"id":18552,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/18532\/revisions\/18552"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=18532"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=18532"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=18532"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=18532"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}