Magnetic properties and molecular structure of complexes of substituted pyrazine ligands co-ordinated to iron(II) and copper(II) low dimensional antiferromagnetic interactions in diaquabis(pyrazinecarboxylato)iron(II)

Abstract

The preparation and magnetic properties at 6–300 K are reported for the complexes [FeL₂(H₂O)₂], [Fe(HL′)₂]·3H₂O, and [Cu(HL′)₂]·3H₂O, where HL = pyrazinecarboxylic acid and H₂L′= 2,3-pyrazinedicarboxylic acid. The crystal structure of the compound [FeL₂(H₂O)₂] is reported; it crystallizes as a monomer but the crystalline lattice contains an extensive network of hydrogen bonding with the hydrogen bonding along one direction shorter than in other directions. The magnetic data for [FeL₂(H₂O)₂] exhibit a maximum in the temperature-dependent magnetic susceptibility at around 15 K, consistent with the Fisher linear-chain model (J/k=–1.3 K). The complex [Cu(HL′)₂]·3H₂O exhibits no magnetic interaction, whilst [Fe(HL′)₂]·3H₂O shows a low-temperature drop in the effective magnetic moment consistent with a zero-field splitting of the spin S= 2 multiplet (D/k= 12.6 K). Crystal data for [FeL₂(H₂O)₂] : space group P2₁/c, Z= 2, a= 5.238(2), b= 11.198(2), c= 10.337(3)Å, β= 100.74(5)°, R= 0.077 for 604 reflections.