title: Cobalt(II) and cobalt(III) dipicolinate complexes: solid state, solution, and in vivo insulin-like properties.
abstract: The synthesis and characterization of Co(II) and Co(III) 2,6-pyridinedicarboxylate (dipic(2-)) complexes are reported. Solid-state X-ray characterizations were performed on [Co(H(2)dipic)(dipic)].3H(2)O and [Co(dipic)(mu-dipic)Co(H(2)O)(5)].2H(2)O. Two coordination modes not previously observed in dipicolinate transition metal complexes were observed in these complexes; one involves metal coordination to the short C-O (C=O) bond, and the other involves metal coordination to a protonated oxygen atom. Solution studies, including paramagnetic NMR and UV-vis spectroscopy, were done showing the high stability and low lability of the Co(III) complex, whereas the Co(II) complexes exhibited ligand exchange in the presence of excess ligand. The [Co(dipic)(2)](2-) complex has pH dependent lability and in this regard is most similar to the [VO(2)dipic](-) complex. The [Co(dipic)(2)](2-) was found to be effective in reducing the hyperlipidemia of diabetes using oral administration in drinking water in rats with STZ-induced diabetes. Oral administration of VOSO(4) was used as a positive control for metal efficacy against diabetes. In addition to providing a framework to evaluate structure-function relationships of various transition metal complexes in alleviating the symptoms of diabetes, this work describes novel aspects of structural and solution cobalt chemistry.
authors.affiliation: Department of Chemistry, College of Natural Sciences, Colorado State University, Fort Collins, CO 80523-1872, USA.
authors.forename: Luqin
authors.initials: L
authors.lastname: Yang
authors.forename: Debbie C
authors.initials: DC
authors.lastname: Crans
authors.forename: Susie M
authors.initials: SM
authors.lastname: Miller
authors.forename: Agnete
authors.initials: A
authors.lastname: la Cour
authors.forename: Oren P
authors.initials: OP
authors.lastname: Anderson
authors.forename: Peter M
authors.initials: PM
authors.lastname: Kaszynski
authors.forename: Michael E
authors.initials: ME
authors.lastname: Godzala
authors.forename: LaTanya D
authors.initials: LD
authors.lastname: Austin
authors.forename: Gail R
authors.initials: GR
authors.lastname: Willsky