First-row transition-metal complexes based on a carboxylate polychlorotriphenylmethyl radical: trends in metal-radical exchange interactions.
We report the synthesis, crystal structures, and magnetic properties of a series of mononuclear, metal-radical complexes with first-row transition-metal ions using a new class of radical-based ligands, the polychlorinated triphenylmethyl (PTM) radicals. Crystal structures of three new PTM-based complexes of general formula M(PTMMC)2(py)4-x(H2O)x [PTMMC = PTM radical functionalized at the para position with one carboxylic group; M = Zn(II), x = 2 (1); M = Ni(II), x = 1 (2); M = Co(II), x = 1 (3)] show similar molecular structures in which mononuclear complexes are formed by an octahedral metal ion coordinated by two monodentated PTMMC units. From a magnetic point of view, these similar configurations describe a quasilinear, trimeric magnetic model (PTMMC-M(II)-PTMMC), in which the metal [Ni(II) or Co(II)]-radical magnetic-exchange coupling constants have been determined for the first time. In all of these complexes, the temperature dependence of the magnetic susceptibility reveals moderate antiferromagnetic-exchange coupling constants between the PTMMC radicals and Ni(II) (2J/kB = -47.1 K) and Co(II) ions (2J/kB = -15.2 K) based on the exchange Hamiltonian H = -2JSM(Srad1 + Srad2).
Maspoch
Daniel
D
Institut de Ciència de Materials de Barcelona, CSIC, Campus Universitari de Bellaterra, 08193 Cerdanyola, Spain.
Domingo
Neus
N
Ruiz-Molina
Daniel
D
Wurst
Klaus
K
Hernandez
Joan Manel
JM
Lloret
Francesc
F
Tejada
Javier
J
Rovira
Concepció
C
Veciana
Jaume
J
D002264:Carboxylic Acids / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005609:Free Radicals / Q000737:chemistry; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry*; D008280:Magnetics; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D028561:Transition Elements / Q000737:chemistry*
D002264:Carboxylic Acids; D005609:Free Radicals; D006843:Hydrocarbons, Chlorinated; D009942:Organometallic Compounds; D028561:Transition Elements