title: Slow Relaxation of Magnetization in an Isostructural Series of Zinc-Lanthanide Complexes: An Integrated EPR and AC Susceptibility Study.
abstract: We report the synthesis, structure, and spectroscopic and dynamic magnetic properties of a series of heterodinuclear complexes, [ZnLn(LH4 )2 ](NO3 )3 ⋅6 H2 O (Ln=Nd, Tb, Dy, Ho, Er, and Yb), with the singly deprotonated form of a new compartmentalized Schiff-base ligand, LH5 . The Ln(III) ions in these systems show a distorted square-antiprism geometry with an LnO8 coordination sphere. EPR spectroscopy and DC magnetic studies have shown that the anisotropic nature of the complexes is far more complicated than predicted on the basis of a simple electrostatic model. Among the investigated systems, only the Dy(III) derivative showed single-ion magnet behavior, in zero and an applied magnetic field, both in pure polycrystalline samples and in a series of polycrystalline samples with different degrees of dilution at the single-crystal level in the isostructural Y(III) derivative. The rich dynamics observed as functions of frequency, field, and temperature reveals that multiple relaxation mechanisms are at play, resulting in a barrier of 189 cm(-1) , which is among the highest reported for a dinuclear Zn-Dy system. Analysis of the dynamic behavior as a function of dilution degree further evidenced the persistence of non-negligible intermolecular interactions, even at the lowest concentration of 1 %.
authors.affiliation: INSTM Research Unit - LAMM, Dipartimento di Chimica "U-Schiff", Università di Firenze, via della Lastruccia, 3-13, Sesto Fiorentino (FI), 50019, Italy.
authors.forename: Asma
authors.initials: A
authors.lastname: Amjad
authors.affiliation: Inorganic Chemistry Laboratory, Faculty of Chemistry, University of Bucharest, Str. Dumbrava Rosie nr. 23, 020464-, Bucharest, Romania. augustin.madalan@chimie.unibuc.ro.
authors.forename: Augustin M
authors.initials: AM
authors.lastname: Madalan
authors.affiliation: Inorganic Chemistry Laboratory, Faculty of Chemistry, University of Bucharest, Str. Dumbrava Rosie nr. 23, 020464-, Bucharest, Romania.
authors.forename: Marius
authors.initials: M
authors.lastname: Andruh
authors.affiliation: INSTM Research Unit - LAMM, Dipartimento di Chimica "U-Schiff", Università di Firenze, via della Lastruccia, 3-13, Sesto Fiorentino (FI), 50019, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Caneschi
authors.affiliation: INSTM Research Unit - LAMM, Dipartimento di Chimica "U-Schiff", Università di Firenze, via della Lastruccia, 3-13, Sesto Fiorentino (FI), 50019, Italy. lorenzo.sorace@unifi.it.
authors.forename: Lorenzo
authors.identifier: http://orcid.org/0000-0003-4785-1331
authors.initials: L
authors.lastname: Sorace
keywords: AC susceptibility; EPR spectroscopy; lanthanides; single-ion magnets; zinc