Assembly of dinuclear copper(ii) secondary building units into polymeric complexes: crystal structures and magnetic properties

Abstract

Four Cu(II) complexes, the one-dimensional [Cu(HL¹)₂(CuCl₄)]_n (1), {[Cu₂(L¹)₂(N(CN)₂)(CH₃OH)](ClO₄)}_n (2), dinuclear [Cu₂(L²)₂Cl₂] (3), and two-dimensional layered [Cu₂(L²)₂(N(CN)₂)₂]_n (4) were synthesized by Cu(II) salts (CuCl₂·2H₂O or Cu(ClO₄)₂·6H₂O), alkanol bidentate ligands trans-2-(1-pyrazolyl)cyclohexanol (HL¹) or 3,5-dimethyl-N-hydroxyethyl-pyrazolyl (HL²) together with sodium dicyanamide. For complex 1, the bridging chlorine atoms of the tetrahedral [CuCl₄]²⁻ moieties are located at the Jahn–Teller axis of the elongated octahedral Cu(II), forming an alternate elongated-octahedral-tetrahedral Cu(II) chain complex. For complexes 2, 3 and 4, the alkyl oxygen atoms of the deprotonated ligands HL¹ and HL² bridge two Cu(II) ions, yielding a dinuclear Cu(II) unit [Cu₂(L^x)₂]²⁺ (x = 1, 2), and one- or two-dimensional complexes via bridging dicyanamide ligands. Complex 1 shows weak ferromagnetic coupling, whilst complexes 2–4 display strong antiferromagnetic coupling or are even nearly diamagnetic due to the large Cu–O–Cu bond angles.