title: Switching nuclearity and Co(II) content through stoichiometry adjustment: {Co(II)6Co(III)3} and {Co(II)Co4(III)} mixed valent complexes and a study of their magnetic properties.
abstract: We are reporting two new mixed valent Co(ii)/Co(iii) polynuclear complexes, {Co(II)6Co(III)3} and {Co(II)Co(III)4}, bearing different amount of Co(ii) ions in their cores, through the employment of the multidentate triethanolamine (teaH3) ligand in different stoichiometric ratios. We present a complete picture of the magnetic behaviour of both complexes through a combined usage of the susceptibility, magnetization and X-band EPR data as well as broken-symmetry DFT calculations. Compound shows an atypical spin-only behaviour, probably due to the presence of four and five coordinated Co(ii) sites as well as highly distorted six coordinated Co(ii) ions, promoting a high degree of orbital contribution quenching. Through the usage of a simplified exchange coupling scheme and relying on DFT based magneto-structural correlation we have been able to explain the observed diamagnetic ground state. Concerning compound , DC magnetic data supported by X-band EPR measurements suggest the existence of anisotropy with a zero-field splitting parameter D, at least in the range of 2-10 cm(-1). In agreement with this description, a slow relaxation of magnetization is observed after applying a small external magnetic field, under AC measurements. Field and temperature dependence of the characteristic relaxation time establishes a thermal barrier for magnetization reversal of about 25 cm(-1), which is in good agreement with the energy splitting of the |±1/2〉 and |±3/2〉 doublets established from static magnetic measurements.
authors.affiliation: Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE (CONICET), Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina. albores@qi.fcen.uba.ar.
authors.forename: Alejandro V
authors.initials: AV
authors.lastname: Funes
authors.forename: Luca
authors.initials: L
authors.lastname: Carrella
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Sorace
authors.forename: Eva
authors.initials: E
authors.lastname: Rentschler
authors.forename: Pablo
authors.initials: P
authors.lastname: Alborés