Hetero triply-bridged dinuclear copper(ii) compounds with ferromagnetic coupling: a challenge for current density functionals

Abstract

However, none of the functionals is able to reproduce the fine details along the series which constitutes an excellent benchmark for future developments.

Electronic Structure and Magnetic Coupling of Pure and Mg-Doped KCuF3

“…It is well known that the evaluation of the magnetic coupling depends critically on the functionals adopted in the computation [41], and our computations confirm that a change in the percentage of Hartree-Fock exchange included in the Hamiltonian induces dramatic changes in the evaluation of terms. Even worse, literature studies prove that no systematic rule allows a priori defining the best functional for a given system.…”

Synthesis, Crystal Structures and Magnetic Properties of a Linear Trinuclear Cu(II) Complex [Cu3(ClCH2COO)6(bpy)2] and a Dinuclear Complex [Cu2(bpy)2(μ‐OH)(μ‐OH2) (μ‐ClCH2COO)](ClO4)2

“…However, the wide range of 2 J values (39 to 151 cm –1 ), is not correlated with the bridge angle alone, but is a function of more than one structural parameter as well as differences in the ligand fields. The 2 J values for a limited set of seven compounds were previously correlated with the Cu⋅⋅⋅Cu distance wherein an approximate linear correlation was found . That model would predict a 2 J of 84 cm –1 for the present compound which is about 12% larger than observed.…”

“…The magnetic data for the known carboxylato‐hydroxo‐aqua triply‐bridged dinuclear Cu(II) complexes, are included in Table . Both Cu(II) sites are five coordinate with slight to moderate deviation from SP geometry.…”

“…For the ferromagnetic cation in the dinuclear compound 2 , the broken symmetry result for J is 42.2 cm –1 (without spin projection) which compares well with the experimental value of 36.9 cm –1 . It should be mentioned that different equations have been employed in the literature, for relating the energy gap between low spin (broken symmetry) and high spin states to the magnetic exchange parameter ( J ). It has been recently pointed out that the spin projected expression which corrects for spin contamination in the broken symmetry sate is preferable when advanced correlation functionals are employed in DFT, especially those with enhanced Fock exchange ,,.…”

Mixed-ligand MnIIand CuIIcomplexes with alternating 2,2′-bipyrimidine and terephthalate bridges

“…One overview and a possible classification of binuclear five-coordinated Cu II complexes has been published by Youngme et al (2008). Many of these compounds contain the already mentioned dpya, phen and bipy as N,N 0 -chelating ligands (Wu et al, 1992;Chailuecha et al, 2006;Chen et al, 2008;Youngme et al, 2008;Li et al, 2009;Wannarit et al, 2013). Six-coordinated complexes of this type are also known (Elliot et al, 1998;Xiao et al, 2008) but are not so common.…”