Cobalt-thioalkylazoimidazole complexes: Structures, spectra and redox properties

• Published in: Polyhedron 2009-11, Vol.28 (16), p.3519-3525
• Main Authors: Nandi, S., Bannerjee, D., Datta, P., Lu, T.-H., Slawin, A.M.Z., Sinha, C.
• Format: Article
• Language: English
• Subjects: 2-{(Thioalkyl)arylazo}imidazole; Cobalt(II); Cyclic voltammetry; DFT computation; Octahedral; X-ray structure
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2009.04.043

[Co(SRaaiNR /) 2](ClO 4) 2 compounds have been isolated from the reaction between Co(ClO 4) 2.6H 2O and SRaaiNR /. A mixture of Co(OAc) 2·4H 2O, NH 4SCN 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 =. 1-Alkyl-2-{( o-thioalkyl)phenylazo}imidazole (SRaaiNR /, 1) reacts with Co(ClO 4) 2·6H 2O to form [Co(SRaaiNR /) 2](ClO 4) 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 ClO 4 − anions shows disorder and forms an (imidazole)C–H···O(ClO 3) interaction leading to a 1-D chain. Co(OAc) 2.4H 2O and SRaaiNR / react in the presence of NH 4SCN (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.