Chemical tuning by 5-Methyl and N-Methyl-substitution in heptanuclear complexes effects multistability investigated by Mössbauer spectroscopy

The precursors [Fe(III)(N − R − L)Cl] (N − R − LH2=N,N′-bis(2′-hydroxy- 5′-methyl-benzyliden)-1,7-diamino-4-R-4-azaheptane, R = H, methyl(Me)) are high-spin (S = 5/2) complexes. The Lewis-acidic precursors are combined with Lewis- Base-bridging-units [M(CN) x ] y − (M = Fe(II), Ru(II), Co(III)) to form heptanuclear star-shaped [M{CN-Fe(III)(N − R − L)} x ]Cl y molecular switches. The star-shaped compounds are high-spin systems at room temperature. On cooling to 20 K some of the compounds exhibit multistability, i.e. several iron(III) centers within a molecule switch to the low-spin state as shown by Mossbauer spectroscopy.