Copper(II) azide complexes of 1-alkyl-2-(arylazo)imidazoles: Structure and magnetism

Tetranuclear Cu(II)-azido complexes of the composition [Cu(RaaiR′)(N3)2]4 have been synthesized by reacting 1-alkyl-2-(arylazo)imidazole (RaaiR′), Cu(OAc)2 · H2O and NaN3 in 1:1:2 mole proportion [RaaiR′; R = H (3), Me (4); R′ = Me (a), Et (b)]. The structure of [Cu(HaaiMe)(N3)2]4 (3a) has been confirmed by an X-ray diffraction study. The tetranuclear copper core is generated by dimerisation via μ1,1-N3 of two dimer units. In each dimer one copper centre is five-coordinated (CuN5) and the other one is six-coordinated (CuN6). Variable temperature magnetic measurements of 3a show the occurrence of ferromagnetic (J1 = +25.3 cm−1) and antiferromagnetic (J2 = −4.7 cm−1) interactions through the double and single end-on azido bridges, respectively. Upon addition of excess ligand, a 2-methoxy ethanol solution of the tetranuclear complex fragmented into a mononuclear copper(II) complex of the formula [Cu(RaaiR′)2(N3)2], and in one case, [Cu(HaaiEt)2(N3)2], the structure was established by X-ray diffraction.

Graphical abstractTetranuclear Cu(II)-azido complexes of composition [Cu(RaaiR′)(N3)2]4 have been synthesized and one of them has been characterized by X-ray crystallography. Variable temperature magnetic measurement indicates ferromagnetic and antiferromagnetic interactions, with J1 = +25.3 cm−1 and J2 = −4.7 cm−1.Figure optionsDownload full-size imageDownload as PowerPoint slide