DSpace
 

DSpace at IIT Bombay >
IITB Publications >
Article >

Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/10054/12031

Title: A new octahedral cobalt(III) complex of (1,8)-bis(2-hydroxybenzamido)-3,6-diazaoctane incorporating phenolate-amide-amine coordination: synthesis, X-ray crystal structure, ligand substitution and redox activity with sulfur(IV) and L-ascorbic acid
Authors: NAYAK, S
DASH, AC
LAHIRI, GK
Keywords: manganese(iv) complex
superoxide-dismutase
iron(iii) complexes
catalyzed aquation
aqueous-solution
kinetics
mechanism
ion
thiocyanate
azide
Issue Date: 2008
Publisher: SPRINGER
Citation: TRANSITION METAL CHEMISTRY, 33(1), 39-53
Abstract: The octahedral complex, [Co-III(HL)]center dot 9H(2)O (H4L = (1,8)-bis(2-hydroxybenzamido)-3,6-diazaoctane) incorporating bis carboxamido-N-,bis sec-NH, phenolate, and phenol coordination has been synthesized and characterized by analytical, NMR (H-1, C-13), e.s.i.-Mass, UV-vis, i.r., and Raman spectroscopy. The formation of the complex has also been confirmed by its single crystal X-ray structure. The cyclic voltammetry of the sample in DMF ([TEAP] = 0.1 mol dm(-3), TEAP = tetraethylammonium perchlorate) displayed irreversible redox processes, [Co-III(HL)] -> [Co-IV(HL)](+) and [Co-III(HL)] -> [Co-II(HL)](-) at 0.41 and - 1.09 V (versus SCE), respectively. A slow and H+ mediated isomerisation was observed for the protonated complex, [Co-III(H2L)](+) (pK = 3.5, 25 degrees C, I = 0.5 mol dm(-3)). H(2)Asc was an efficient reductant for the complex and the reaction involved outer sphere mechanism; the propensity of different species for intra molecular reduction followed the sequence: [{[Co-III(HL)],(H(2)Asc)}- H](-) <<< {[Co-III(H2L)],(H(2)Asc)}(+) \{[Co-III(HL)],(H(2)Asc)}. A low value (ca. 3.7 x 10(-10) dm(3) mol(-1) s(-1), 25 degrees C, I = 0.5 mol dm(-3)) for the self exchange rate constant of the couple [Co-III(HL)]/[Co-II(HL)](-) indicated that the ligand HL3- with amido (N-) donor offers substantial stability to the Co-III state. HSO3- and [Co-III(HL)] formed an outer sphere complex {[Co-III(HL)],(HSO3-)}, which was slowly transformed to an inner sphere S-bonded sulfito complex, [Co-III(H2L)(HSO3)] and the latter was inert to reduction by external sulfite but underwent intramolecular S-IV -> Co-III electron transfer very slowly.
URI: http://dx.doi.org/10.1007/s11243-007-9012-4
http://dspace.library.iitb.ac.in/xmlui/handle/10054/12031
http://hdl.handle.net/10054/12031
ISSN: 0340-4285
Appears in Collections:Article

Files in This Item:

There are no files associated with this item.

View Statistics

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

 

Valid XHTML 1.0! DSpace Software Copyright © 2002-2010  Duraspace - Feedback