Naphthylazoimidazole complexes of cobalt(II): Synthesis structure and electrochemistry

The reaction of 1-alkyl-2-(naphthyl-(α/β)-azo)imidazoles [α-NaiR, (1) and β-NaiR (2) where R = Me (a), Et (b), CH2Ph (c)] with Co(OAc)2 · 4H2O and NaN3 in methanol solution has synthesised [Co(α/β-NaiR)2(N3)2] (3, 4). The complexes have been characterized by spectroscopic data and structurally confirmed by single crystal X-ray diffraction data in the case of [Co(β-NaiEt)2(N3)2] (4b). The structure is a severely distorted tetrahedron of CoN4 coordination in which β-NaiEt serves as a monodentate imidazole-N donor ligand. The distortion arises from two weak interactions from Co⋯N(azo) (N(azo) from β-NaiEt). Two weak transitions observed at >600 nm are due to the structural distortion. Cyclic voltammetry shows a high potential Co(III)/Co(II) couple along with ligand reductions in the complexes. The tris-chelates, [Co(NaiR)3]2+, are also characterized.

Graphical abstractThe title complexes have been synthesized and characterized by X-ray structure determination in one case. Cyclic voltammetry shows a high potential Co(III)/Co(II) redox response along with azo reductions. The tris-chelated complexes are unstable to moisture.Figure optionsDownload full-size imageDownload as PowerPoint slide