Structure, optical and magnetic behaviour of meso-tetraphenyl-porphyrinatoiron(III) tetracyanoethenide, [FeIII(TPP)]+[TCNE].-*

The direct redox reaction between tetracyanoethylene (TCNE) and meso-tetraphenylporphyrinatoiron(II), [FeII(TPP)], formed the electron transfer salt (ETS) [FeIII(TPP)][TCNE], which has been structurally, spectroscopically, and magnetically characterized. It has an extended one-dimensional linear chain with coordination polymer motif comprised of [FeIII(TPP)]_x0002_+ and bridging u-[TCNE](.-)_x0001__x0001_ with Fe-NTCNE distance 1.889(2) A(o). This coordination geometry is consistent with a low-spin iron(III) ion, i.e., one electron transfer from FeII to TCNE produces S = 1/2 [FeIII(TPP)]_x0002_ + having a (dxy)2(dyz,dzx)3 configuration and S = 1/2 [TCNE]_x0001__x0001_.-. 57Fe Mossbauer data, o = 0.28 mm s-1 and 0E = 2.19 mm s-1 at 77 K, also support the low-spin state.