Models for Biological Trinuclear Copper Clusters. Characterization and Enantioselective Catalytic Oxidation of Catechols by the Copper(II) Complexes of a Chiral Ligand Derived from (S)-(-)-1,1'-Binaphthyl-2,2'-Diamine
Articolo
Data di Pubblicazione:
2004
Citazione:
Models for Biological Trinuclear Copper Clusters. Characterization and Enantioselective Catalytic Oxidation of Catechols by the Copper(II) Complexes of a Chiral Ligand Derived from (S)-(-)-1,1'-Binaphthyl-2,2'-Diamine / M.C. Mimmi, M. Gullotti, L. Santagostini, G. Battaini, E. Monzani, R. Pagliarin, G. Zoppellaro, L. Casella. - In: DALTON TRANSACTIONS. - ISSN 1477-9226. - 2004:14(2004 Jun 11), pp. 2192-2201.
Abstract:
The dinuclear and trinuclear Cu(II) complexes of an octadentate ligand derived from (S)-1,1′-binaphthyl-2,2′-diamine
have been prepared and characterized by UV/Vis, CD, EPR and NMR spectroscopy. The ligand contains two tridentate
aminobis(benzimidazole) donor arms connected to a central bidentate diaminobinaphthyl linker, which hosts the chiral
unit. In the dinuclear Cu complex the ligation occurs essentially within the tridentate arms of the ligand. The two Cu
centers are EPR nonequivalent and noninteracting. The EPR data suggests that one of the Cu ions additionally interacts
with one of the tertiary aminonaphthyl donors. In the trinuclear complex the two aminonaphthyl donors bind the third Cu
ion. The EPR spectrum of this complex shows the signal for a mononuclear Cu(II) center bound to a tridentate arm, while
the remaining two Cu(II) centers are coupled through hydroxo groups. The CD spectrum shows that in the free ligand a
severe reduction of the dihedral angle between the naphthyl groups from the strain free range occurs. This conformation is
stabilized by ring stacking interactions with the benzimidazole groups. On complex formation this interaction is removed
because the benzimidazole groups are involved in metal binding. In the dinuclear Cu complex the conformation of the
binaphthyl chromophore probably approaches the strain free range, while in the trinuclear Cu complex a marked flattening
of the dihedral angle between the two naphthyl rings occurs. Both complexes are active catalysts in the oxidation of L-/DDopa
derivatives to quinones. High enantioselectivity is observed in the oxidation of L-/D-Dopa methyl ester catalyzed by
the dinuclear Cu complex, which exhibits strong preference for the D enantiomer. The enantioselectivity is largely lost for
the trinuclear Cu complex.
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
M.C. Mimmi, M. Gullotti, L. Santagostini, G. Battaini, E. Monzani, R. Pagliarin, G. Zoppellaro, L. Casella
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