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Compound <jats:bold>12<\/jats:bold> crystallizes in the orthorhombic space group <jats:italic>Pna<\/jats:italic>2<jats:sub>1<\/jats:sub> with <jats:italic>a<\/jats:italic> = 20.752(5), <jats:italic>b<\/jats:italic> = 5.826(5), and <jats:italic>c<\/jats:italic> = 34.309(5) \u00c5. X\u2010ray crystal structure determination, electronic spectroscopy, variable\u2010temperature EPR spectroscopy, SQUID measurements and DFT computations (UB3LYP\/6\u201031+G*) were used to study the molecular conformations and electronic spin coupling in this series of molecules. Whereas compounds <jats:bold>7\u2009b<\/jats:bold>, <jats:bold>7\u2009c<\/jats:bold>, and <jats:bold>7\u2009d<\/jats:bold> are quite stable both in solution and in the solid state, <jats:bold>7\u2009a<\/jats:bold> and <jats:bold>12<\/jats:bold> undergo a partial electronic rearrangement to both a diamagnetic quinonoidal form and a monoradical species owing to the fact that they correspond to the open form of a \u03c0\u2010conjugated Kekul\u00e9 structure. In the solid state, magnetic measurements indicate that the diradicals are all antiferromagnetically coupled, as expected from their topology. These interactions are best reproduced by means of a \u201cBleaney\u2013Bowers\u201d model that gives values of <jats:italic>J<\/jats:italic> = \u2212142.0 cm<jats:sup>\u22121<\/jats:sup> for <jats:bold>7\u2009a<\/jats:bold>, \u22121.8 cm<jats:sup>\u22121<\/jats:sup> for <jats:bold>7\u2009b<\/jats:bold>, \u22121.3 cm<jats:sup>\u22121<\/jats:sup> for <jats:bold>7\u2009c<\/jats:bold>, \u22124.2 cm<jats:sup>\u22121<\/jats:sup> for <jats:bold>7\u2009d<\/jats:bold>, and \u2212248.0 cm<jats:sup>\u22121<\/jats:sup> for <jats:bold>12<\/jats:bold>. The temperature dependence of the EPR half\u2010field transition in frozen dichloromethane solutions is consistent with singlet ground states and thermally accessible triplet states for diradicals <jats:bold>7\u2009b<\/jats:bold>, <jats:bold>7\u2009c<\/jats:bold>, and <jats:bold>7\u2009d<\/jats:bold> with \u0394<jats:italic>E<\/jats:italic><jats:sub>T\u2013S<\/jats:sub> values of 3.48, 2.09, and 8 cm<jats:sup>\u22121<\/jats:sup>, respectively. No evidence of a populated triplet state was found for diradicals <jats:bold>7\u2009a<\/jats:bold> and <jats:bold>12<\/jats:bold>. Similarities between the \u0394<jats:italic>E<\/jats:italic><jats:sub>T\u2013S<\/jats:sub> and <jats:italic>J<\/jats:italic> values (\u0394<jats:italic>E<\/jats:italic><jats:sub>T\u2013S<\/jats:sub> = \u22122 <jats:italic>J<\/jats:italic>) clearly show the intramolecular origin of the observed antiferromagnetic interaction. Analyses of the data with a \u201cKarplus\u2013Conroy\u201d\u2010type equation enabled us to establish that the silole ring, as a whole, allows a more efficient magnetic coupling of the two nitroxide radicals attached to its 2,5\u2010positions than the thiophene ring. This superiority probably originates from the nonaromaticity of the silole which thus permits a better magnetic interaction through it. DFT calculations also support the experimental results, indicating that the magnetic exchange pathway preferentially involves the carbon \u03c0 system of the silole.<\/jats:p>","DOI":"10.1002\/chem.200501280","type":"journal-article","created":{"date-parts":[[2006,5,8]],"date-time":"2006-05-08T04:31:58Z","timestamp":1147062718000},"page":"5547-5562","source":"Crossref","is-referenced-by-count":23,"title":["Experimental and Theoretical Studies of Magnetic Exchange in Silole\u2010Bridged Diradicals"],"prefix":"10.1002","volume":"12","author":[{"given":"Nans","family":"Roques","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Philippe","family":"Gerbier","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ulrich","family":"Schatzschneider","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jean\u2010Pascal","family":"Sutter","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Philippe","family":"Guionneau","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jos\u00e9","family":"Vidal\u2010Gancedo","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jaume","family":"Veciana","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Eva","family":"Rentschler","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Christian","family":"Gu\u00e9rin","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2006,7,7]]},"reference":[{"key":"e_1_2_6_1_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0022-3093(01)01129-2"},{"key":"e_1_2_6_2_2","doi-asserted-by":"publisher","DOI":"10.1002\/(SICI)1521-3765(20000502)6:9<1683::AID-CHEM1683>3.0.CO;2-M"},{"key":"e_1_2_6_3_2","doi-asserted-by":"publisher","DOI":"10.1002\/(SICI)1521-4044(199808)49:8<379::AID-APOL379>3.0.CO;2-Z"},{"volume-title":"Handbook of Organic Conductive Molecules and Polymers, Vol. 2","year":"1997","author":"Ishikawa M.","key":"e_1_2_6_4_2"},{"key":"e_1_2_6_5_2","doi-asserted-by":"publisher","DOI":"10.1002\/0470857250.ch22"},{"key":"e_1_2_6_6_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0166-1280(99)00028-7"},{"key":"e_1_2_6_7_2","doi-asserted-by":"publisher","DOI":"10.1246\/bcsj.69.2327"},{"key":"e_1_2_6_8_2","doi-asserted-by":"publisher","DOI":"10.1002\/ange.19891011206"},{"key":"e_1_2_6_8_3","doi-asserted-by":"publisher","DOI":"10.1002\/anie.198916271"},{"key":"e_1_2_6_9_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0022-328X(01)01257-8"},{"key":"e_1_2_6_10_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja962829c"},{"key":"e_1_2_6_11_2","doi-asserted-by":"publisher","DOI":"10.1246\/cl.2001.98"},{"key":"e_1_2_6_12_2","doi-asserted-by":"publisher","DOI":"10.1039\/b405238b"},{"key":"e_1_2_6_13_2","doi-asserted-by":"publisher","DOI":"10.1021\/cm960554u"},{"key":"e_1_2_6_14_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0277-5387(03)00300-0"},{"key":"e_1_2_6_15_2","doi-asserted-by":"publisher","DOI":"10.1021\/ic00075a080"},{"key":"e_1_2_6_16_2","doi-asserted-by":"publisher","DOI":"10.1021\/ic00107a028"},{"key":"e_1_2_6_17_2","doi-asserted-by":"publisher","DOI":"10.1039\/b107430j"},{"key":"e_1_2_6_18_2","doi-asserted-by":"publisher","DOI":"10.1021\/ol017093p"},{"key":"e_1_2_6_19_2","doi-asserted-by":"publisher","DOI":"10.1021\/om030389"},{"key":"e_1_2_6_20_2","doi-asserted-by":"publisher","DOI":"10.1016\/0379-6779(95)03287-8"},{"key":"e_1_2_6_21_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja993151e"},{"key":"e_1_2_6_22_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja001920k"},{"key":"e_1_2_6_23_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0277-5387(01)00589-7"},{"key":"e_1_2_6_24_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.jpcs.2003.11.018"},{"key":"e_1_2_6_25_2","doi-asserted-by":"publisher","DOI":"10.1039\/a804491k"},{"key":"e_1_2_6_26_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0022-328X(02)01152-X"},{"key":"e_1_2_6_27_2","doi-asserted-by":"publisher","DOI":"10.3987\/S(B)-1982-01-0117"},{"key":"e_1_2_6_28_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0277-5387(01)00614-3"},{"key":"e_1_2_6_29_2","doi-asserted-by":"publisher","DOI":"10.1080\/10587259508055274"},{"key":"e_1_2_6_30_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00012a029"},{"key":"e_1_2_6_31_2","doi-asserted-by":"publisher","DOI":"10.1103\/PhysRevB.37.785"},{"key":"e_1_2_6_32_2","doi-asserted-by":"publisher","DOI":"10.1016\/0009-2614(89)87234-3"},{"key":"e_1_2_6_33_2","doi-asserted-by":"publisher","DOI":"10.1063\/1.464913"},{"key":"e_1_2_6_34_2","unstructured":"M. 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