Journal article Open Access

Synthesis, characterization and electrochemical properties of the transition metal (Fe-Zn) complexes of 2,4-di-tert-butyl-6-(pyridin-2-ylazo)-phenol ligand

Ipsita Chatterjee; Mou Chakraborty; Pradip Ghosh; Sreebrata Goswami

Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700 032, India


Present address: Organic Chemistry and Catalysis, Utrecht University, 3584 CG Utrecht, The Netherlands

Manuscript received 30 June 2018, accepted 13 July 2018

Herein we report five homoleptic, six-coordinated 3d metal complexes [FeII(L)2], 1; [CoIII(L)2]ClO4, [2]ClO4; [NiII(L)2], 3; [CuII(L)2], 4; [ZnII(L)2], 5 containing tridentate anionic azo-aromatic NNO donor ligand 2,4-di-tert-butyl-6-(pyridin-2-ylazo)-phenol (HL). The complexes are synthesized from the reactions between hydrated metal perchlorates and the ligand, HL in 1:2 molar ra­tio in methanol. One-electron oxidation of the iron complex, 1 by iodine resulted in the isolation of respective cationic com­plex [FeIII(L)2]I3, [1]I3. All these six complexes are characterized by single crystal X-ray diffraction as well as several spectro­scopic techniques and magnetic measurements. While complexes 1, [2]ClO4 and 5 are diamagnetic the other three complexes [1]I3, 3 and 4 behave as simple paramagnets. Redox properties of both HL and metal complexes are studied by cyclic voltammetry. Analysis of three-dimensional X-ray structure together with 57Fe Mössbauer spectrum for 1 established a low-spin bis-ligated FeII configuration. The oxidized iron complex [1]I3 displayed a metal centered axial EPR signal at g\(\perp\) = 1.995 and g\(\parallel\) = 1.993 and its Mössbauer spectrum together with magnetic moment established a low-spin FeIII configuration reveal­ing that redox events in case of iron are metal centered. One electron reduction of the Co-complex, [2]ClO4 produced a CoII­complex, which showed 8-lines EPR spectrum at gav. = 1.997.

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