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Issue 38, 2012
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The intricate paramagnetic state of [Os(Q)2(bpy)]+, Q = 4,6-di-tert-butyl-o-iminobenzoquinone

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The combination of two highly non-innocent ligands with a third-row transition metal produces the title complex ion which was crystallised as [Os(Q)2(bpy)](ClO4)·C6H6 (Q = 4,6-di-tert-butyl-o-iminobenzoquinones, bpy = 2,2-bipyridine) and could be structurally characterised to exhibit a tris-chelate situation at the metal with trans-positioned N and cis-positioned O donor atoms. The metrical ligand parameters are in agreement with two partially reduced ligands. A 3-spin interaction (Q˙)OsIII(Q˙) can rationalise the observed S = 1/2 situation with ligand-centred resulting spin. Ligand-based spin is confirmed by DFT (calculated spin populations Q: 1.113; Os: −0.113; bpy: 0.001) and is also apparent from the EPR signal (g1 1.981, g2 1.955, g3 1.803, Δg 0.178, 〈g〉 1.915) which is influenced by the high spin–orbit coupling constant of the osmium centre. The susceptibility measurements reveal antiferromagnetic behaviour. A one-electron oxidation and two one-electron reductions could be monitored spectroelectrochemically (UV-VIS-NIR) and analysed by TD-DFT, in comparison with the results from the ruthenium analogue. The analysis reflects the strong orbital mixing between the metal and the two Q-ligand MOs.

Graphical abstract: The intricate paramagnetic state of [Os(Q)2(bpy)]+, Q = 4,6-di-tert-butyl-o-iminobenzoquinone

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The article was received on 25 Apr 2012, accepted on 19 Jul 2012 and first published on 23 Jul 2012

Article type: Paper
DOI: 10.1039/C2DT30903C
Citation: Dalton Trans., 2012,41, 11675-11683
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    The intricate paramagnetic state of [Os(Q)2(bpy)]+, Q = 4,6-di-tert-butyl-o-iminobenzoquinone

    D. Das, T. M. Scherer, A. Das, T. K. Mondal, S. M. Mobin, J. Fiedler, J. L. Priego, R. Jiménez-Aparicio, W. Kaim and G. K. Lahiri, Dalton Trans., 2012, 41, 11675
    DOI: 10.1039/C2DT30903C

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