Copper(II)–Lanthanoid(III) Complexes of Binucleating Ligands Derived from 3-Formylsalicylic Acid and Diamines

Abstract

Heterometal binuclear complexes, [CuLn(fsaen)(H2O)n](NO3) (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu; n=4–5) and [CuLn(fsapn)(H2O)4](NO3) (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, or Dy) have been synthesized and characterized, where H4fsaen and H4fsapn denote N,N′-bis(3-carboxysalicylidene)ethylenediamine and N,N′-bis(3-carboxysalicylidene)-1,2-propanediamine, respectively. The ligand field band due to the copper(II) ion bound to the N2O2-site is at 18.5×103–19.5×103 cm−1 for [CuLn(fsaen)(H2O)n](NO3) and 18.4×103–19.2×103 cm−1 for [CuLn(fsapn)(H2O)4](NO3), which are higher frequencies than those of the mononuclear complexes, [Cu(H2fsaen)](H2O)0.5 and [Cu(H2fsapn)](H2O)0.5 (18.3×103 and 18.4×103 cm−1, respectively). When the complexes are dissolved in pyridine (Py), dimethyl sulfoxide (DMSO), or N,N-dimethylformamide (DMF), the d–d band frequency decreases in the order of the solvent DMSO>DMF>Py for the binuclear complexes, whereas it decreases in the order of DMF>DMSO>Py for the mononuclear complexes. These trends were discussed in terms of the different affinities of solvent molecules for copper(II) and lanthanoid(III) ions. No significant magnetic spin-exchange interaction occurred between metal ions.

Three Novel Rare-earth Complexes with Nitronyl Nitroxide Radical [RE(hfac)3 (NITPhOCH3)2] [RE = GdIII, YIII and ErIII]: Syntheses, Crystal Structures and Magnetic Properties

“…The very small J indicates a very weak intramolecular exchange interaction between Gd III and the radical. This may be attributed to the fact that 4f electrons are shielded by the outer shell electrons [15]. The positive value of J shows the ferromagnetic coupling between gadolinium(III) and NITPhOCH 3 , in agreement with previous results for the gadolinium(III) complexes with other paramagnetic ligands [5a, 16].…”

Synthesis and Magnetism of Copper(II)-lanthanide(III)-copper(II) Heterotrinuclear Complexes with N,N′-bis [2-(dimethylamino)ethyl]oxamidocopper(II)

“…The small J value may account for the fact that 4f-electrons are shielded by the outer shell electrons [29]. However, the ferromagnetic interaction existing in the present complex between Gd III and Cu II , which was also observed in previous reports of polynuclear copper(II)-gadolinium(III) clusters with different bridges [12,13,21,[30][31][32], is interesting because gadolinium(III) has unpaired electrons in 7f orbitals and at least one of them, or one linear combination, can give a nonzero overlap with the magnetic orbitals on copper(II). Thus, this gives an antiferromagnetic coupling.…”

Synthesis and magnetic properties of copper(II)–lanthanide(III) heterobinuclear complexes with N,N′-bis[3-(dimethylamino)propyl]oxamido as ligand

“…On the basis of the Boltzmann distribution, the two states are both populated at room temperature owing to very weak interaction (vide infra). Thus, the dissymmetric broad signals may be ascribed to the complex in these spin states [30].…”

“…It is noted that the spectrum of the complex exhibits a dissymmetric broad band around g ¼ 2:1, which also indicates a magnetic spin-exchange interaction between gadolinium(III) and copper(II) ions [30]. Since there is a lack of structural data for the complex, it is difficult to quantitatively interpret this broad band.…”

“…Moreover, the very good agreement factor (F) also indicates that the contribution of the intermolecular antiferromagnetic interactions and/or the zero-field splitting effects in the ground state is evidently weaker than the intramolecular spin-exchange and can be neglected. The small J value may account for the fact that 4f-electrons are shielded by the outershell electrons [30]. However, the ferromagnetic coupling existing in the present complex between gadolinium (III) and copper(II) ions, which was also observed in other copper(II)-gadolinium(III) clusters [2][3][4], is interesting because gadolinium(III) has unpaired electrons in all seven 4f-orbitals, and it might be expected that at least one or one linear combination of these orbitals would overlap with the semioccupied orbital on copper(II).…”