Cobalt-thioalkylazoimidazole complexes: Structures, spectra and redox properties

1-Alkyl-2-{(o-thioalkyl)phenylazo}imidazole (SRaaiNR/, 1) reacts with Co(ClO4)2·6H2O to form [Co(SRaaiNR/)2](ClO4)2 (2). The single crystal X-ray structure of one of the complexes of 2 shows a tridentate chelation N(imidazole), N(azo), S(thioether) system. In the structure one of ClO4− anions shows disorder and forms an (imidazole)C–H···O(ClO3) interaction leading to a 1-D chain. Co(OAc)2.4H2O and SRaaiNR/ react in the presence of NH4SCN (1:1:2 mole ratio) in methanol and the complex [Co(SRaaiNR/)2(SCN)2] (3) has been separated. The single crystal X-ray structure determination has established the structure of the complexes in which the ligand SRaaiNR/ acts in a bidentate N(imidazole), N(azo) chelation mode. A cyclic voltammogram shows a Co(III)/Co(II) oxidative response at 0.6–0.8 V and azo reductions. DFT computation using optimized geometry support the electronic spectral and redox properties of the complexes.

Graphical abstract[Co(SRaaiNR/)2](ClO4)2 compounds have been isolated from the reaction between Co(ClO4)2.6H2O and SRaaiNR/. A mixture of Co(OAc)2·4H2O, NH4SCN and SRaaiNR/ has isolated [Co(SRaaiNR/)2(SCN)2]. In the previous compound, the ligand acts as a SRaaiNR/ tridentate N(imidazole), N(azo), S(thioether) chelator, whilst in the latter compound it serves as a bidentate N(imidazole), N(azo) chelator. Structures are established by X-ray crystallography. Redox chemistry shows Co(III)/Co(II) and azo reductions, azo/azo− and azo−/azo=.Figure optionsDownload full-size imageDownload as PowerPoint slide