Dinuclear mixed-valence Co(III)Co(II) complexes derived from a macrocyclic ligand: unique example of a Co(III)Co(II) complex showing catecholase activity.
The work in this paper presents the syntheses, characterization, catecholase activity, and electrospray ionization mass spectroscopic (ESI-MS positive) study of three mixed-valence dinuclear Co(III)Co(II) complexes of composition [Co(III)Co(II)L(N(3))(3)]·CH(3)CN (1), [Co(III)Co(II)L(OCN)(3)]·CH(3)CN (2), and [Co(III)Co(II)L(μ-CH(3)COO)(2)](ClO(4)) (3), derived from a tetraimino diphenolate macrocyclic ligand H(2)L, obtained on [2 + 2] condensation of 4-ethyl-2,6-diformylphenol and 2,2'-dimethyl-1,3-diaminopropane. While 1 and 2 are diphenoxo-bridged, 3 is a heterobridged bis(μ-phenoxo)bis(μ-acetate) system. Utilizing 3,5-di-tert-butyl catechol (3,5-DTBCH(2)) as the substrate, the catecholase activity of all the three complexes has been checked in methanol/acetonitrile/N,N-dimethyl formamide. While 2 and 3 are inactive, complex 1 shows catecholase activity with turnover numbers of 482.16 h(-1) and 45.38 h(-1) in acetonitrile and methanol, respectively. Electrospray ionization mass (ESI-MS positive) spectra of complexes 1-3 have been recorded in acetonitrile solutions and the positive ions have been well characterized. The ESI-MS positive spectrum of complex 1 in the presence of 3,5-DTBCH(2) has also been recorded and, interestingly, two positive ions [Co(III)Co(II)L(N(3))(2)(3,5-DTBCH(-))H](+) and [Co(II)Co(II)L(μ-3,5-DTBCH(2-))Na](+) have been identified.
Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India. sm_cu_chem@yahoo.co.in
Samit
S
Majumder
Suraj
S
Mondal
Pascale
P
Lemoine
Sasankasekhar
S
Mohanta
D004156:Catechol Oxidase / Q000378:metabolism*; D002396:Catechols / Q000378:metabolism; D003035:Cobalt / Q000737:chemistry*; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D007700:Kinetics; D008024:Ligands; D047028:Macrocyclic Compounds / Q000737:chemistry; D008968:Molecular Conformation
D002396:Catechols; D056831:Coordination Complexes; D008024:Ligands; D047028:Macrocyclic Compounds; D003035:Cobalt; D004156:Catechol Oxidase; C034221:catechol