Formation and structure of a complex of sucrose with cobalt(III)bis(phenanthroline).
Sucrose forms a dicationic complex with cobalt(III)bis(phenanthroline) which can be isolated as the sparingly water-soluble triiodide salt or the water-soluble chloride. The circular dichroism (CD) spectrum demonstrates the Delta configuration at Co(III) and the presence of two phenanthroline and one sucrose residues in the complex. The O-2(g)--O-1(f) distance in crystalline sucrose permits strain-free coordination of these centers with Co(III) and in the complex the H-1,1'(f) singlet of sucrose separates into a pair of doublets. The 1H NMR spectrum in DMSO-d(6) shows that OH-2(g) is deprotonated and the signal of OH-1(f) is shifted strongly downfield by complexation with Co(III). Coordination involving glucose and fructose residues is consistent with neither alpha-methyl glucoside nor fructofuranose forming mixed complexes with phenanthroline. Structure simulation with the semi-empirical PM3(tm) basis set indicates that complexation by O-2(g) and OH-1(f) can give a Delta-complex with little structural distortion, whereas in hypothetical Lambda-complexes there is distortion of the sucrose residue. Observation of an NOE involving the sucrose and phenanthroline residues supports the postulated structure of the Delta-complex.
Parada
J
J
Departamento de Química Inorgánica y Analitica, Facultad de Ciencias Químicacs y Farmaceuticas, Universidad de Chile, Santiago, Chile.
Bunel
S
S
Ibarra
C
C
Larrazabal
G
G
Moraga
E
E
Gillitt
N D
ND
Bunton
C A
CA
D002942:Circular Dichroism; D003035:Cobalt / Q000737:chemistry / Q000378:metabolism; D005632:Fructose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010618:Phenanthrolines / Q000737:chemistry*; D013395:Sucrose / Q000737:chemistry / Q000378:metabolism
D008024:Ligands; D009942:Organometallic Compounds; D010618:Phenanthrolines; C421919:delta-bis(phenanthroline)(sucrose)cobalt(III); D005632:Fructose; D003035:Cobalt; D013395:Sucrose; D005947:Glucose