title: Magnetic frustration and spin disorder in isostructural M(mu-OH2)2[Au(CN)2]2 (M = Mn, Fe, Co) coordination polymers containing double aqua-bridged chains: SQUID and microSR studies.
abstract: A series of isostructural M(mu-OH(2))(2)[Au(CN)(2)](2) (M = Co, Fe, and Mn) coordination polymers was synthesized from the reaction of M(II) with [(n)Bu(4)N][Au(CN)(2)]. The basic structural motif for these polymers is analogous to that of previously reported Cu(II)- and Ni(II)-containing polymers and contains repeating double aqua bridges between metal centers that yield a chain structure with pendant [Au(CN)(2)](-) units. The aqueous reaction with Fe(III) yields Fe(mu-OH(2))(mu-OH)[Au(CN)(2)](2), which has a similar structure. The magnetic properties of these polymers were investigated by a combination of SQUID magnetometry and zero-field muon spin relaxation. The double aqua bridges were found to mediate ferromagnetic interactions along the chains in the Co(II)-containing polymer, whereas intrachain antiferromagnetic interactions are present in the Fe(II)-, Fe(III)-, and Mn(II)-containing polymers. Weak magnetic interchain interactions mediated through hydrogen bonds, involving the bridging water molecules and the pendant cyanide groups, are also present. In zero field, the interchain interactions yield a phase transition to a disordered spin-frozen magnetic state below 2-5 K for every polymer. However, the degree of spin disorder varies considerably, depending on the metal center.
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Julie
authors.initials: J
authors.lastname: Lefebvre
authors.forename: Pooja
authors.initials: P
authors.lastname: Tyagi
authors.forename: Simon
authors.initials: S
authors.lastname: Trudel
authors.forename: Vighen
authors.initials: V
authors.lastname: Pacradouni
authors.forename: Christina
authors.initials: C
authors.lastname: Kaiser
authors.forename: Jeff E
authors.initials: JE
authors.lastname: Sonier
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Leznoff