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- Multiple spin transition (2) (entfernen)
Spin transition in heptanuclear star-shaped iron(III)-antimony(V) NCS- and CN-bridged compounds
(2009)
The precursor [FeIII(L)Cl] (LH2 = N,N'-bis(2'-hydroxy-benzyliden)-1,6-diamino-3-azahexane) has been prepared and Mössbauer spectroscopy assigned a high-spin (S = 5/2) state at room temperature. The precursor is combined with the bridging units [SbV(X)6]- (X = CN-, NCS-) to yield star-shaped heptanuclear clusters [(LFeIII-X)6SbV]Cl5. The star-shaped compounds are in general high-spin systems at room temperature. On cooling to 20 K some of the iron(III) centers switch to the low-spin state as indicated by Mössbauer spectroscopy, i.e. multiple electronic transitions. While the cyano-bridged complex performs a multiple spin transition the thiocyanate-compound shows no significant population at both temperatures.
The precursor [FeIII(L)Cl] (LH<sub2 = N,N'-bis(2'-hydroxy-benzyliden)-1,6-diamino-3-N-hexane is a high-spin (S = 5/2) complex. This precursor is combined with the bridging units [SnIV(X)4] (X = CN-, NCS-) to yield star-shaped pentanuclear clusters, [(LFeIII-X)4Sn]Cl4. For X = CN- the 57Fe-Mössbauer data show a multiple spin transition between iron(III) in the high-spin and low-spin state, while the 119mSn-Mössbauer data indicate a valence tautomerism between Sn(IV) and Sn(II). Changing the bridging unit from X = CN- to X = NCS- turns the switchability off.