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

• Published in: Polyhedron 2006-10, Vol.25 (14), p.2764-2772
• Main Authors: Ray, Umasankar, Sarker, Kamal Krishna, Mostafa, Golam, Lu, Tian-Huey, El Fallah, M. Salah, Sinha, Chittaranjan
• Format: Article
• Language: English
• Subjects: 1-Alkyl-2-(arylazo)imidazoles; Copper(II)-azide; Magnetic properties; Tetranuclear
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2006.04.007

Tetranuclear Cu(II)-azido complexes of composition [Cu(RaaiR′)(N 3) 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 J 1 = +25.3 cm −1 and J 2 = −4.7 cm −1. Tetranuclear Cu(II)-azido complexes of the composition [Cu(RaaiR′)(N 3) 2] 4 have been synthesized by reacting 1-alkyl-2-(arylazo)imidazole (RaaiR′), Cu(OAc) 2 · H 2O and NaN 3 in 1:1:2 mole proportion [RaaiR′; R = H ( 3), Me ( 4); R′ = Me ( a), Et ( b)]. The structure of [Cu(HaaiMe)(N 3) 2] 4 ( 3a) has been confirmed by an X-ray diffraction study. The tetranuclear copper core is generated by dimerisation via μ 1,1-N 3 of two dimer units. In each dimer one copper centre is five-coordinated (CuN 5) and the other one is six-coordinated (CuN 6). Variable temperature magnetic measurements of 3a show the occurrence of ferromagnetic ( J 1 = +25.3 cm −1) and antiferromagnetic ( J 2 = −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(N 3) 2], and in one case, [Cu(HaaiEt) 2(N 3) 2], the structure was established by X-ray diffraction.