Three new dinuclear bis-μ-azido-bridged Cu(II) compounds with di-2-pyridylamine as a ligand: Syntheses, X-ray structure and magnetic measurements

Three new dinuclear copper(II) compounds: [Cu2(dpyam)2(μ1,1-N3)2(O2CH)2] (1), [Cu2(dpyam)2(μ1,1-N3)2(O2CCH3)2] (2) and [Cu2(dpyam)2(μ1,1-N3)2(O2CCH2CH3)2] (3) have been synthesized in order to investigate the magnetic superexchange interaction pathway between coupled copper(II) centers. All three compounds consist of a dinuclear unit in which both Cu(II) ions are bridged by double end-on azido ligands providing a distorted square pyramidal geometry, τ = 0.38, 0.48 and 0.30, with a CuN4O chromophore. The Cu⋯Cu separations are 3.195, 3.200 and 3.247 Å for compounds 1, 2 and 3, respectively. The magnetic susceptibility measurements, measured from 5 to 300 K, revealed a medium to weak ferromagnetic exchange interactions between the copper(II) ions dominated by the bridging azido ligands, with a singlet-triplet splitting (J) of 63.3, 63.8 and 5.1 cm−1, for compounds 1, 2 and 3, respectively. A large zero-field splitting of about 0.4 cm−1 is observed in the EPR for compounds 1 and 2.