Abstracts 2001

Abstract of Publication No. 388

Ralph Schenker, Høgni Weihe, Hans U. Güdel and Berthold Kersting
Exchange Pathways in Tris-m-thiolato Bridged [Cr2L3](CIO4)2CI·H2O·MeOH (L = 2,6-Bis(aminomethyl)-4-tert-butyl-thiophenolate)
Inorg. Chem. 40, 3355-3362 (2001)      Full Text (PDF)      DOI-Link     

Abstract: From polarized optical absorption and emission spectra of the tris-m-thiolato bridged [Cr2L3](CIO4)2CI·H2O·MeOH (L = 2,6-Bis(aminomethyl)-4-tert-butyl-thiophenolate) 1 in the visible and near UV, the exchange splittings of the 4A2 ground and the 2E and 2T1 excited states are determined. In view of the large Cr-Cr distance of 3.01, the antiferromagnetic ground state splitting with J = 78cm1 (H = J(SA·SB)) is large compared to other triply bridged Cr3+ dimers. This can be rationalized using a model based on a valence bond approach, in which the exchange splittings are derived from configuration interactions between the ground electron configuration and ligand-to-metal (LMCT) as well as metal-to-metal (MMCT) charge-transfer configurations. It allows us to distinguish the interactions via ligand orbitals from the direct interactions between the metal-centered orbitals. We compare our results with those obtained for the tri-m-hydroxo-bridged [Cr2(OH)3(tmtame)2](NO3)3 (tmtame = N,N',N''-trimethyl-1,1,1-tris(aminomethyl)ethane) 2. In the latter the interactions via the ligands are negligible, whereas they play an important role in 1, due to the softness of the sulfur ligand atoms.

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