Design of novel inorganic-organic hybrid materials based on iron-chloranilate mononuclear complexes: Characteristics of hydrogen-bond-supported layers toward the intercalation of guests

Novel intercalation compounds constructed from the common two-dimensional hydrogen-bond-supported layers and functional guests {(H(0.5)phz)(2)[Fe(CA)(2)(H2O)(2)].2H(2)O}(n) (1), {[Fe(Cp)(2)][Fe(CA)(2)(H2O)(2)]}(n) (2), {[Fe(Cp*)(2)][Fe(CA)(2)(H2O)(2)]}(n) (3), and {(TTF)(2)[Fe(CA)(2)(H2O)(2)]}(n) (4) (H(2)CA = chloranilic acid, phz = phenazine, [Fe(CP)(2)] = ferrocene, [Fe(Cp*)(2)] = decamethylferrocene, TTF = tetrathiafulvalene) are described. The guest cations are introduced between the [Fe(CA)(2)(H2O)(2)](m-)} layers by electrostatic (1-4) and pi-pi stacking (3, 4) interactions. [Fe(Cp*)(2)](+) cations in 3 are stacked on each other making tilted columns which are included in the channel created by the chlorine atoms of CA(2-) dianions. TTF cations in 4 are stacked face to face with two types of S...S distances (type A; 3.579(3) Angstrom, and type B; 3.618(3) Angstrom) making a columnar structure. The TTF cations in the stacked column have a head-to-tail arrangement with respect to the iron-chloranilate layer. Mossbauer spectroscopy suggests that [Fe(CA)(2)(H2O)(2)](m-) anion in 3 is consistent with high-spin (S = 5/2) iron(III) ions and [Fe(CP*)(2)](+) in the low-spin (S = 1/2) iron(III) ions. In 4, Mossbauer spectroscopy shows high-spin iron(II) ions (IS 1.10 mm.s(-1) and QS = 1.66 mm.s(-1) at 297 K) and high-spin iron(III) ions (IS = 0.42 mm.s(-1) and QS = 1.27 mm.s(-1) at 297 K), suggesting that the anionic layer of iron-chloranilate has a valence-trapped mixed-valence state. At the temperature range of 77-300 K, the compounds 1, 2, and 3 are EPR silent, whereas the EPR spectrum of 4 shows two types of signals with g = 2.008 indicating the radical form of TTF.