Complexes of cobalt(III) with phenolate-containing polydentate ligands and bovine serum apo-transferrin: Towards creating spectroscopic models for cobalt(III)-tyrosinate interactions

Musa S. Shongwe, Said K M Al-Hatmi, Helder M. Marques, Rachel Smith, Ryoji Nukada, Masahiro Mikuriya

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Reaction of each member of a series of variously substituted N-(2-hydroxybenzyl)glycinate (hbg 2-) ligands [5-bromo- (5-Br-hbg 2-); 5-chloro- (5-Cl-hbg 2-); 3,5-dichloro- (3,5-Cl 2-hbg 2-); 5-chloro-3-methyl- (5,3-Cl,Me-hbg 2-); and 3,5-dimethyl- (3,5-Me 2-hbg 2-)] with cobalt(II) in stoichiometric amounts under ambient conditions afforded the Co III complex anions of the general formulatrans,trans,trans-[Co(hbg) 2] -. Single-crystal X-ray analyses of [C 5H 10NH 2]-trans,trans,trans-[Co(3,5-Cl 2-hbg) 2]3 and [C 5H 10NH 2]-trans,trans,trans-[Co(3,5-Me 2-hbg) 2]5 {[C 5H 10- NH 2] piperidinium counter ion} have revealed similar structural motifs of these compounds. Each of the crystal structures shows two non-equivalent complex anions in the unit cell connected through hydrogen bondingvia the piperidinium cation. The two hbg 2- ligands in each complex ion are arranged facially around the cobalt(III) ion and each ligand employs a phenolate oxygen, an amine nitrogen and a carboxylate oxygen to form a distorted octahedral geometry with C i symmetry. These compounds (1-5) serve as spectroscopic models for the interaction of cobalt(III) with tyrosinate ligands. The electronic spectrum of the compound [C 5H 10NH 2]-trans,trans,trans-[Co(5,3-Cl, Me-hbg) 2]4 bears a striking resemblance to that of the complex of cobalt(III) with bovine serum transferrin, [Co 2BTf]. In contrast to previous studies on the spectroscopy of the transferrins, one of the two ligand-field transitions expected to occur in [Co 2BTf] is evident in the electronic spectrum of this derivative of bovine serum transferrin in vitro. One of the fascinating characteristics of thetrans,trans,trans-[Co(hbg) 2] - model system is the solvent dependence of the optical spectra.

Original languageEnglish
Pages (from-to)4064-4069
Number of pages6
JournalJournal of the Chemical Society, Dalton Transactions
Issue number21
Publication statusPublished - 2002


ASJC Scopus subject areas

  • Chemistry(all)

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