Cooperative influence of pseudohalides and ligand backbone of Schiff-bases on nuclearity and stereochemistry of cobalt(iii) complexes: experimental and theoretical investigation. Issue 44 (25th October 2017)

• Record Type: Journal Article
• Authors: Mandal, Arnab; Dasgupta, Sanchari; Ganguly, Sumi; Bauzá, Antonio; Frontera, Antonio; Das, Debasis
• Is Part Of: Dalton transactions. Volume 46:Issue 44(2017)
• Page Start: 15257
• Page End: 15268
• Publication Date: 2017-10-25
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c7dt03040a
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The ligand backbone effect of homologous Schiff-bases in combination with influences of SCN − and N3 − is instrumental in controlling nuclearity and stereochemistry of catecholase active cobalt(iii ) complexes. Abstract : Four cobalt(iii ) complexes, [Co(HL 1 )(NCS)2 (EtOH)] (1 ), [Co2 (L 1 )2 (N3 )2 ] (2 ) and [Co(HL 2 )(NCS)2 (EtOH)] (3 ), [Co(HL 2 )(N3 )2 ] (4 ) were synthesized from two Schiff-base ligands namely, ( E )-2-((2-(2-hydroxyethylamino)ethylimino)methyl)phenol (H2 L 1 ) and ( E )-2-((3-(2-hydroxyethylamino)propylimino)methyl)phenol (H2 L 2 ), respectively. All the four complexes have been thoroughly characterised by using various physicochemical studies such as UV-Vis, FT-IR, ESI-MS, EPR and single crystal X-ray diffraction. Depending on flexibility of the ligand backbone subtle structural differences are observed in the synthesized complexes. In complex1 the two thiocyanate ligands are trans to each other whereas in complex3 they are cis to each other with addition of one additional methylene (–CH2 –) group to the ligand system. Complex2 is dinuclear while complex4 is mononuclear in the presence of the azide co-anionic ligand. Theoretical studies are carried out in order to rationalize the structural differences observed in the complexes. Catecholase like activity of all the four complexes were performed in N, N -dimethylformamide (DMF) using 3, 5-di- tert -butylcatechol (3, 5-DTBC) as a model substrate. Complex2 was found to exhibit the highest activity. Mechanistic investigation of the catecholase like activity revealed the formation of the imine radical during catalytic reactions of complexes2 and4 which are further corroborated by the EPR study.