Magnetic Cationic Copper(II) Chains and a Mononuclear Cobalt(II) Complex Containing [Ln(hfac)4]- Blocks as Counterions.

Abstract

Four new heterospin compounds with molecular formula {[Cu2(hfac)3(TlTrzNIT)2][Ln(hfac)4]} n·C7H16 (LnIII = Gd (1), Tb (2), or Dy (3)) and [Co(hfac)(TlTrzNIT)2][Dy(hfac)4] (4), where hfac is hexafluoroacetylacetonato and TlTrzNIT is the nitronylnitroxide radical 1-( m-tolyl)-1 H-1,2,3-triazole-4-(4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), were obtained. All structures were determined by single-crystal X-ray diffraction. In compounds 1-3, the TlTrzNIT radical is bridge-coordinated to copper(II) ions, leading to positively charged copper(II)-radical chains containing [Ln(hfac)4]- as counterions. In compound 4, the cobalt(II) ion is coordinated to two TlTrzNIT radicals and one hfac ligand in bidentate mode leading to a mononuclear cationic complex that contains [Dy(hfac)4]- as counterion. Magnetic measurements of all complexes were performed. Magnetic data were fit considering the contributions of the copper(II)-radical chain and a paramagnetic gadolinium(III) ion for 1. The sign and magnitude of the magnetic coupling constants extracted from the fit were confirmed by density functional theory calculations. The obtained spin topology shows an alternated ferro-antiferromagnetic chain. Field-induced single molecule magnet behavior was observed for the Dy derivatives 3 and 4, in agreement with CASSCF calculations performed for the latter system.