{"id":3604,"date":"2011-03-05T08:25:02","date_gmt":"2011-03-05T08:25:02","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=3604"},"modified":"2015-06-04T07:23:00","modified_gmt":"2015-06-04T06:23:00","slug":"lapis-lazuli-the-colour-of-ultramarine","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=3604","title":{"rendered":"Lapis lazuli: the colour of ultramarine."},"content":{"rendered":"<div class=\"kcite-section\" kcite-section-id=\"3604\">\n<p>My colleague Bill Griffith has <a href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=3507\" target=\"_blank\">again<\/a> come up with another colour challenge: that of the ancient semi-precious stone <em><strong>Lapis Lazuli<\/strong><\/em>, mined in the mountains of Afghanistan for more than 6000 years and used by painters in some medieval paintings of the Virgin, the Wilton diptych etc.<\/p>\n<div id=\"attachment_3605\" style=\"width: 179px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/03\/337px-Lapis_lazuli_block.jpg\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3605\" class=\"size-full wp-image-3605\" title=\"337px-Lapis_lazuli_block\" src=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/03\/337px-Lapis_lazuli_block.jpg\" alt=\"\" width=\"169\" height=\"300\" \/><\/a><p id=\"caption-attachment-3605\" class=\"wp-caption-text\">Lapis Lazuli (photo from Wikipedia).<\/p><\/div>\n<p>The formula is (approximately): (Na,Ca)<sub>8<\/sub>(AlSiO<sub>4<\/sub>)<sub>6<\/sub>(S,SO<sub>4<\/sub>,Cl)<sub>1-2<\/sub>, which sounds a bit of a challenge! But, as a very recent article points out<span id=\"cite_ITEM-3604-0\" name=\"citation\"><a href=\"#ITEM-3604-0\">[1]<\/a><\/span> the component that imparts the colour is the sulfur, \u00a0more specifically present in the stone as the \u00a0S<sub>3<\/sub><sup>&#8211;<\/sup> radical anion. No recent calculation of the \u00a0UV\/Vis spectrum of this simple triatomic has been reported, so here goes. A <a href=\"http:\/\/hdl.handle.net\/10042\/to-7459\" target=\"_blank\">\u03c9B97XD\/aug-cc-pVQZ calculation<\/a>, embedded in a continuum solvent field of water (which serves to compactify the otherwise diffuse anionic aspect) and with TD-DFT applied, shows the following (you will need an SVG enabled Web browser to see the spectrum. I am here promoting the use of this graphical standard, which differs from normal images in scaling as you resize the page size with no loss of resolution).<br \/>\n<a href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/03\/lapis.svg\"><img decoding=\"async\" class=\"aligncenter size-full wp-image-3606\" title=\"lapis\" src=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/03\/lapis.svg\" alt=\"\" width=\"500\" \/><\/a><\/p>\n<p>The \u03bb<sub>max<\/sub> is ~650nm calculated and\u00a0~619nm measured (as a solution in an ionic liquid).\u00a0Not bad agreement! The molecular orbitals involved in the excitation are shown below.<\/p>\n<table border=\"0\">\n<tbody>\n<tr>\n<td>\n<p><div id=\"attachment_3611\" style=\"width: 182px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3611\" class=\"size-full wp-image-3611\" title=\"lapis-HDOMO\" src=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/03\/lapis-HDOMO1.jpg\" alt=\"\" width=\"172\" height=\"113\" srcset=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/03\/lapis-HDOMO1.jpg 515w, https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/03\/lapis-HDOMO1-300x196.jpg 300w\" sizes=\"auto, (max-width: 172px) 100vw, 172px\" \/><p id=\"caption-attachment-3611\" class=\"wp-caption-text\">Highest doubly occupied MO. Click for 3D.<\/p><\/div><\/td>\n<td>\n<p><div id=\"attachment_3610\" style=\"width: 169px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3610\" class=\"size-full wp-image-3610\" title=\"lapis-SOMO\" src=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/03\/lapis-SOMO.jpg\" alt=\"\" width=\"159\" height=\"119\" srcset=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/03\/lapis-SOMO.jpg 477w, https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/03\/lapis-SOMO-300x224.jpg 300w\" sizes=\"auto, (max-width: 159px) 100vw, 159px\" \/><p id=\"caption-attachment-3610\" class=\"wp-caption-text\">Lowest singly occupied MO. Click for 3D.<\/p><\/div><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Such a precious colour, and produced using such a cheap material!<\/p>\n<h2>References<\/h2>\n    <ol class=\"kcite-bibliography csl-bib-body\"><li id=\"ITEM-3604-0\">?. Boros, M.J. Earle, M.A. G\u00eelea, A. Metlen, A. Mudring, F. Rieger, A.J. Robertson, K.R. Seddon, A.A. Tomaszowska, L. Trusov, and J.S. Vyle, \"On the dissolution of non-metallic solid elements (sulfur, selenium, tellurium and phosphorus) in ionic liquids\", <i>Chem. Commun.<\/i>, vol. 46, pp. 716-718, 2010. <a href=\"https:\/\/doi.org\/10.1039\/b910469k\">https:\/\/doi.org\/10.1039\/b910469k<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> <!-- kcite-section 3604 -->","protected":false},"excerpt":{"rendered":"<p>My colleague Bill Griffith has again come up with another colour challenge: that of the ancient semi-precious stone Lapis Lazuli, mined in the mountains of Afghanistan for more than 6000 years and used by painters in some medieval paintings of the Virgin, the Wilton diptych etc. The formula is (approximately): (Na,Ca)8(AlSiO4)6(S,SO4,Cl)1-2, which sounds a bit [&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":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[4],"tags":[492,491,468,215,469,339],"ppma_author":[2661],"class_list":["post-3604","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","tag-afghanistan","tag-bill-griffith","tag-lapis-lazuli","tag-missouri","tag-trisulfide-radical-anion","tag-web-browser"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.3 - 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