Novel Oxygen Chirality Induced by Asymmetric Coordination of an Ether Oxygen Atom to a Metal Center in a Series of Sugar-Pendant Dipicolylamine Copper(II) Complexes

Abstract

Six sugar-pendant 2,2'-dipicolylamine (DPA) ligands (L1-3 and L'1-3) have been prepared. OH-protected and unprotected D-glucose, D-mannose, and D-xylose were attached to a DPA moiety via an O-glycoside linkage. X-ray crystallography of the copper(II) complexes (1-5) with these ligands revealed that the anomeric oxygen atom is coordinated to the metal center in the solid state, generating a chiral center at the oxygen atom. The CD spectra of these copper complexes in methanol or aqueous solution exhibit Cotton effects in the d-d transition region, which indicates that the ether oxygen atoms remain coordinated to the metal center and the oxygen-atom chirality is preserved even in solution. For complexes 1 and 2, the inverted oxygen-atom chirality and chelate-ring conformation in the solid state are well correlated with the mirror-image CD spectra in methanol solution. The concomitant inversion of the asymmetric configuration around the copper center was also observed in a methanol solution of complex 3 and a pyridine solution of complex 2. The square-pyramidal/octahedral copper(II) centers also exhibited characteristic absorption and CD spectra.

Structural and Magnetic Properties of Cu(dpa) X2(dpa = Di-(2-picolyl)amine; X = Cl and Br)

“…Therefore, dpa chelates facially with the copper(II) ion in a folded rearrangement. The meridional 3,6,11 and facial 12 fashions in Cu(II) complexes with dpa ligand are found for some other complexes. The meridional fashion in the present complexes leads to a regular square pyramidal coordination environment.…”

“…For example, carbohydrate-appended dpa metal complexes were suggested as potential imaging agents 1 and sugar-pendant dpa Cu(II) complexes were used to regulate chirality on the copper coordinated oxygen atom. 2,3 Zinc-dpa complexes were applied to fluorescent chemsensors toward a phosphrorylated peptide surface. [4][5][6] Recently, the monomeric structure of copper chloride complexes with dpa, Cu(dpa)Cl 2 , was reported by two research groups 7,8 to study on the C-N bond cleavage of carboxamide by coordination of a neutral tertiary carboxamide nitrogen atom.…”

Synthesis of Rhenium(I) Tricarbonyl Complexes with Carbohydrate‐Pendant Tridentate Ligands and Their Cellular Uptake

“…The preparations of L3 and LЈ3 have been reported previously. [8] Ligands L1H and LЈ1H were synthesized from 2-bromoethyl 2,3,4,6-tetra-Oacetyl-β-d-gluco-or galactopyranoside (1/1Ј) [8] that were reScheme 2. Reagents and conditions: (i) N-(2-pyridylmethyl)glycine tert-butyl ester, DMF; (ii) formic acid; (iii) NaOMe, MeOH; (iv) bis(2-pyridylmethyl)amine.…”

Control of Intramolecular Ether‐Oxygen Coordination in the Crystal Structure of Copper(II) Complexes With Dipicolylamine‐Based Ligands

“…[12,13] Strong binding of the DPA unit to the copper-(II) [14][15][16][17][18][19] assists the asymmetric coordination of the anomeric oxygen atom of the sugar unit to the metal centre in the crystal and in solution.…”