Control of Oxygen Atom Chirality and Chelate Ring Conformation by Protected/Free Sugar Hydroxyl Groups in Glucose-Pendant Dipicolylamine−Copper(II) Complexes

Abstract

A pair of copper(II) complexes 1 and 2 exhibit an enantiomeric chiral center at the oxygen atom that coordinates to the metal center. The configurations of the oxygen atom chirality and the chelate ring conformation are simply controlled by protected/free hydroxyl groups of the sugar moiety, yielding mirror image CD spectra. In this system, repulsive and attractive forces are used to regulate chirality on the copper-coordinated oxygen atom both in the solid state and in solution.

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

“…15 But we examined the controvertible result that Cu-N amine (1.996 Å) is shorter than Cu-N pyridine (2.021 Å) bond length in the present Cu(dpa)Cl 2 complex. Palaniandavar et al 16 reported the structure of [Cu(dpa) 2 ]BF 4 , and they examined the pentacoordinated square pyramidal [Cu(dpa) 2 ] 2+ as well as hexacoordinated octahedral [Cu(dpa) 2 ] 2+ cation in the same cell. In the square pyramidal [Cu(dpa) 2 ] 2+ cation, one dpa coordinated with copper(II) ion meridionally in the equatorial site and the other dpa functioned as a bidentate ligand with one of the pyridine nitrogens in the equatorial site and the amine nitrogen in the axial position.…”

“…Palaniandavar et al 16 reported the structure of [Cu(dpa) 2 ]BF 4 , and they examined the pentacoordinated square pyramidal [Cu(dpa) 2 ] 2+ as well as hexacoordinated octahedral [Cu(dpa) 2 ] 2+ cation in the same cell. In the square pyramidal [Cu(dpa) 2 ] 2+ cation, one dpa coordinated with copper(II) ion meridionally in the equatorial site and the other dpa functioned as a bidentate ligand with one of the pyridine nitrogens in the equatorial site and the amine nitrogen in the axial position. The shorter Cu-N amine bond (Cu-N pyridine = 2.044, 2.027 Å and Cu-N amine = 1.9957 Å) in the equatorial site in a square pyramidal [Cu(dpa) 2 ] 2+ cation is a consequence of the hydrogen bond formation between the uncoordinated pyridine nitrogen in a bidentate dpa ligand and the hydrogen atom in the secondary amino group in an equatorial site.…”

“…In the square pyramidal [Cu(dpa) 2 ] 2+ cation, one dpa coordinated with copper(II) ion meridionally in the equatorial site and the other dpa functioned as a bidentate ligand with one of the pyridine nitrogens in the equatorial site and the amine nitrogen in the axial position. The shorter Cu-N amine bond (Cu-N pyridine = 2.044, 2.027 Å and Cu-N amine = 1.9957 Å) in the equatorial site in a square pyramidal [Cu(dpa) 2 ] 2+ cation is a consequence of the hydrogen bond formation between the uncoordinated pyridine nitrogen in a bidentate dpa ligand and the hydrogen atom in the secondary amino group in an equatorial site. Therefore we suggest that the shorter Cu-N amine than Cu-N pyridine bond can be elucidated from the fact that the amine hydrogens took part in the formation of the hydrogen bond resulting in the stronger bond formation between the amine nitrogen and copper(II) ion in Cu(dpa)Cl 2 crystal.…”

“…The blue block crystals were obtained by a slow evaporation method. The blue Cu(dpa)Br 2 crystals were prepared by a similar method using CuBr 2 The data for X-ray structure determination was collected on a CAD-4 diffractometer equipped with graphite monochromated Mo Kα radiation (λ = 0.71073 Å) at 295 K. The unit cell dimensions were determined on the basis of 25 reflections in the range of 11.40 o < θ < 12.52 o . The data was collected by the ω/2θ scan mode.…”

“…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.…”