Novel layered structures constructed from iron–chloranilate compounds

Abstract

Novel hydrogen bond-supported intercalation compounds, {(G) m [Fe(CA) 2(H 2O) 2]} n (CA 2−=chloranilate, G=guest molecules) have been synthesized and characterized. The compound {(Hpy)[Fe(CA) 2(H 2O) 2](H 2O)} n (py=pyridine) ( 1) crystallizes in the triclinic, space group P1̄ (#2), with a=9.537(5), b=13.563(6), c=9.231(4) Å, α=107.18(4), β=102.33(4), γ=102.12(4)°, V=1065.9(10) Å 3, and Z=2. Compound {(H 2bipy)[Fe(CA) 2(H 2O) 2] 2(H 2O) 2} n (bipy=4,4′-bipyridine) ( 2) crystallizes in the triclinic, space group P1̄ (#2), with a=9.101(1), b=10.379(1), c=12.802(2) Å, α=79.45(1), β=82.67(1), γ=66.32(1)°, V=1086.8(3) Å 3, and Z=1. The structure of 1 consists of mononuclear [Fe(CA) 2(H 2O) 2] − anions, Hpy + cations and uncoordinated water molecules. Four oxygen atoms of two CA 2− anions and two oxygen atoms from two water molecules are coordinated to the iron ion making anionic building blocks of the host layer. The compound of 2 contains the similar monomeric building blocks, H 2bipy 2+ cations and uncoordinated water molecules. In both the compounds the coordination geometry of the building blocks are distorted octahedron, where two water molecules sit on the trans position in 1 and on the cis position in 2. In compound 1 the [Fe(CA) 2(H 2O) 2] − anions make a two-dimensional (2-D) layer supported by hydrogen bonds. Hpy + ions are included in between the layers of 1 supported by hydrogen-bonding and electrostatic interaction with the host layers. In compound 2 the coordinated chloranilate rings of [Fe(CA) 2(H 2O) 2] − anions are stacked upon each other and make a layer with the help of hydrogen bonds. H 2bipy 2+ cations are included in between the layers supported by hydrogen bonding, electrostatic and stacking interaction with coordinated CA 2− ions. The 57Fe Mössbauer spectra of the compounds show that the oxidation state of iron is 3 with IS=0.41 ( 1) and 0.39 mm s −1 ( 2); QS=0.83 ( 1) and 1.29 mm s −1 ( 2) at 296 K, respectively. Compound 2 shows weak antiferromagnetic interaction over the crystal ( θ=−2.3 K).