Copper(II)-histidine stereochemistry. Structure of L-histidinato-D-histidinatodiaquocopper(II) tetrahydrate

Abstract

Crystals of L-histidinato-D-histidinatodiaquocopper(II) tetrahydrate, grown at pH 8, are triclinic, with cell dimensions (subcell) a = 6.894, b = 8.478, c = 9.553 Á, a = 98.61, ß = 116.13, y = 95.88°, space group PI with one formula unit of the complex per cell. Although some weak supercell reflections were present on films, only the subcell data were used to solve (Fourier methods) and refine (final R = 0.076) the structure. The copper atom is octahedrally coordinated by amino and imidazole nitrogens of an L-His and a D-His in a square planar arrangement, and by water molecule oxygens at the axial positions. The Cu-N distances are 2.03 (amino) and 2.00 Á (imidazole) and the Cu-OH2 separation is 2.57 Á. The carboxyl groups of the histidines secondarily coordinate to the copper through hydrogen bonding to the axial waters (O-O distance is 3.01 Á). The structural results, along with consideration of potentiometric titrations and infrared data for the crystals, have been used to postulate a plausible structure for the physiologically important Cu(II)-(L-His)2 complex in solution.

The Octarepeat Domain of the Prion Protein Binds Cu(II) with Three Distinct Coordination Modes at pH 7.4

“…His acts as a bidentate ligand forming a six-membered ring with Cu 2+ as found in crystal structures of Cu−His complexes. 58,59 This coordination mode is fully consistent with the X-and S-band EPR, as well as the ESEEM studies on the methylated and isotopically labeled peptides examined here. Because the proposed component 2 coordination mode ( Figure 6) appears to take up all of the equatorial sites, Cu 2+ should form a 1:1 complex with each octarepeat His.…”

XAS applied to pharmaceuticals: drug administration and bioavailability

“…Results indicate a square planar coordination of the Cu to 2 N atoms at 1.974 Å and 2 O atoms at 2.033 Å, the square being capped by 2 further O atoms at 2.48 Å (Figure 3), in accordance with the crystal structure (Camerman, 1978).…”

Oxorhenium(V) Complexes with the Non-Sulfur-Containing Amino Acid Histidine

“…A cis,cis arrangement would lead to very short contacts between the H 2 atoms of the two coplanar imidazole moieties, and this geometry has not been observed so far in crystal structures of bis-histidine complexes. [36][37][38][39][40][41][42][43][44][45][46][47][48][49] Elemental analysis and mass spectrometry are consistent with the formula proposed. In the IR spectrum, the ν(RedO) vibration is observed as a very strong band at 960 cm -1 , whereas the nearby ligand bands appear weakly at 985 and 1038 cm -1 .…”