Only the first two reduction states have hirtherto been isolated, and closely studied, as crystalline lithium salts containing tetrahydrofuran, LitFePc1.4.5 THF ( I ) and Li2 [FePc].5.5 THF (2) 121. We have now obtained the third and the fourth reduction states in pure crystalline form.
In order to prepare the third reduction state, pure recrystallized (2) in boiling THF was treated with a solution of dilithiobenzophenone in THF in the molar ratio 1 : 3. The third reduction state precipitates immediately. The dry compound forms darkolive-greencrystalsofcompositionLi~[FePcl~8THF ( 3 ) , which are very slightly soluble in THF but somewhat more soluble in dimethylformamide (DMF), to give intensely reddish-violet solutions.
The fourth reduction state was obtained in the same manner, by treatment of (2) with dilithiostilbene, as violet crystals of composition Li4LFePcI-9 THF (4).
The compound dissolves in THF to form an intensely bluish-green solution. It dissolves also in DMF but then rapidly decomposzs with development of a violet color.
The salts (3) and (4) are oxidized in air, with loss of tetrahydrofuran, (4) occasionally becoming incandescent. On oxidation of (3) and (4) with iodine in THF in the absence of air, 2.95 and 3.91 atoms, respectively, of iodine are consumed and [FePc] is formed. The electrolytic character of compounds ( 3) and (4) could be proved by transfer experiments in DMF or THF. Magnetic measurements by Gouy's method at temperatures between 83 and 293 OK substantiated the applicability of the Curie-Weiss law, xM = C / T + 8. Values found wereL31: for (3) : 8 = 35 "K, x (293 "K) = 1 . 4 4 ~ 10-6 cm3/g, g 2.60 B.M. [4] for ( 4 ) : 0 = 12 "K, x (293 OK) = 3.08~ 10-6 cm3/g, ~' ~f f =