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Experimental and Theoretical Studies on Magnetic Exchange in Silole-Bridged Diradicals.

hal.structure.identifierChimie moléculaire et organisation du solide [CMOS]
hal.structure.identifierInstitut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier [ICGM ICMMM]
dc.contributor.authorROQUES, Nans
hal.structure.identifierChimie moléculaire et organisation du solide [CMOS]
hal.structure.identifierInstitut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier [ICGM ICMMM]
dc.contributor.authorGERBIER, Philippe
hal.structure.identifierInstitut fur Pharmazie und Molekulare Biotechnologie
dc.contributor.authorSCHATZSCHNEIDER, Ulrich
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
hal.structure.identifierLaboratoire de chimie de coordination [LCC]
dc.contributor.authorSUTTER, Jean-Pascal
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorGUIONNEAU, Philippe
hal.structure.identifierInstitut de Ciència de Materials de Barcelona [ICMAB]
dc.contributor.authorVIDAL-GANCEDO, Jose
hal.structure.identifierInstitut de Ciència de Materials de Barcelona [ICMAB]
dc.contributor.authorVECIANA, Jaume
hal.structure.identifierInstitut fur Anorganische Chemie und Analytische Chemie [Mainz]
dc.contributor.authorRENTSCHLER, Eva
hal.structure.identifierChimie moléculaire et organisation du solide [CMOS]
hal.structure.identifierInstitut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier [ICGM ICMMM]
dc.contributor.authorGUÉRIN, Christian
dc.date.issued2006
dc.identifier.issn0947-6539
dc.description.abstractEnFive bis(tert-butylnitroxide) diradicals connected by a silole [2,5-R2-3,4-diphenylsilole; R = Me3CN(®O.bul.)Z; Z = p-C6H4 (7a), p-C6H4C6H4-p (7b), 1,4-naphthalenediyl (7c), m-C6H4 (7d)] or a thiophene [2,5-R2-thiophene; R = p-Me3CN(®O.bul.)C6H4 (12)] ring as a coupler were studied. Compd. 12 crystallizes in the orthorhombic space group Pna21 with a 20.752(5), b 5.826(5), and c 34.309(5) .ANG.. X-ray crystal structure detn., electronic spectroscopy, variable-temp. EPR spectroscopy, SQUID measurements and DFT computations (UB3LYP/6-31+G*) were used to study the mol. conformations and electronic spin coupling in this series of mols. Whereas compds. 7b, 7c, and 7d are quite stable both in soln. and in the solid state, 7a and 12 undergo a partial electronic rearrangement to both a diamagnetic quinonoid form and a monoradical species owing to the fact that they correspond to the open form of a p-conjugated Kekule structure. In the solid state, magnetic measurements indicate that the diradicals are all antiferromagnetically coupled, as expected from their topol. These interactions are best reproduced by a Bieaney-Bowers model that gives values of J = -142.0 cm-1 for 7a, -1.8 cm-1 for 7b, -1.3 cm-1 for 7c, -4.2 cm-1 for 7d, and -248.0 cm-1 for 12. The temp. dependence of the EPR half-field transition in frozen CH2Cl2 solns. is consistent with singlet ground states and thermally accessible triplet states for diradicals 7b, 7c, and 7d with DET-S values of 3.48, 2.09, and 8 cm-1, resp. No evidence of a populated triplet state was found for diradicals 7a and 12. Similarities between the DET-S and J values (DET-S = -2 J) clearly show the intramol. origin of the obsd. antiferromagnetic interaction. Analyses of the data with a Karplus-Conroy-type equation enabled the authors 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-positions than the thiophene ring. This superiority probably originates from the non-aromaticity of the silole which thus permits a better magnetic interaction through it. DFT calcns. also support the exptl. results, indicating that the magnetic exchange pathway preferentially involves the C p system of the silole.
dc.language.isoen
dc.publisherWiley-VCH Verlag
dc.title.enExperimental and Theoretical Studies on Magnetic Exchange in Silole-Bridged Diradicals.
dc.typeArticle de revue
dc.identifier.doi10.1002/chem.200501280
dc.subject.halChimie/Chimie organique
dc.subject.halChimie/Chimie théorique et/ou physique
bordeaux.journalChemistry - A European Journal
bordeaux.page5547-5562
bordeaux.volume12
bordeaux.issue21
bordeaux.peerReviewedoui
hal.identifierhal-00186947
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-00186947v1
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