title: Unusual (mu-aqua)bis(mu-carboxylate) bridge in homometallic M(II) (M=Mn, Co and Ni) two-dimensional compounds based on the 1,2,3,4-butanetetracarboxylic acid: synthesis, structure, and magnetic properties.
abstract: The first coordination compounds of 1,2,3,4-butanetetracarboxylate anion (butca4-) of the formula [M2(butca)(H2O)5]n.2nH2O [M=Mn(II) (1), Co(II) (2), and Ni(II) (3)] were prepared and their X-ray crystal structures and magnetic properties investigated. The three complexes have a very similar two-dimensional structure which consists of (4,4) networks, 1 and 2 being isostructural. The tetracarboxylate ligand acts as a 4-fold connector leading to two-dimensional (4,4) networks of metal atoms, this topology being possible because of its planar conformation. The nodes of these networks are formed by dinuclear motifs which exhibit the unusual (mu-aqua)bis(mu-carboxylate) bridging unit which is analogous to that observed in some molecules of biological interest. The variable-temperature magnetic susceptibility measurements of 1-3 show that 1 and 2 are antiferromagnetically coupled systems whereas 3 exhibits a ferromagnetic behavior. The analysis of the magnetic data of 1-3 through a simple dinuclear model allowed the determination of the values of the magnetic coupling (J) -3.6 (1), -1.2 (2), and +1.47 cm(-1) (3) with the Hamiltonian being defined as H=-JSA.SB. The countercomplementarity between the two bridges (aqua and syn-syn carboxylate) accounts for the trend exhibited by the values of the magnetic coupling in this family.
authors: Laboratorio de Rayos X y Materiales Moleculares, Departamento de Física Fundamental II, Facultad de Física, Universidad de La Laguna, Av. Astrofísico Francisco SAnchez s/n, 38206 La Laguna (Tenerife), Spain.
authors: Laura
authors: L
authors: Cañadillas-Delgado
authors: Oscar
authors: O
authors: Fabelo
authors: Jorge
authors: J
authors: Pásan
authors: Fernando S
authors: FS
authors: Delgado
authors: Francesc
authors: F
authors: Lloret
authors: Miguel
authors: M
authors: Julve
authors: Catalina
authors: C
authors: Ruiz-Pérez
mesh_terms: D002073:Butanes / Q000138:chemical synthesis* / Q000737:chemistry; D002264:Carboxylic Acids / Q000138:chemical synthesis / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D002073:Butanes; D002264:Carboxylic Acids; D014867:Water; D003035:Cobalt; D008345:Manganese; C513573:1,2,3,4-butanetetracarboxylic acid; D009532:Nickel