Crystal Structures of Mixed Ligand Copper(II) Complexes Containing l-Amino Acids. III. Aqua(l-histidinato)(l-serinato)copper(II) Trihydrate

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Abstract
The copper(II) complex containing l-histidine and l-serine crystallizes from an aqueous solution. Crystals of aqua(l-histidinato)(l-serinato)copper(II) trihydrate are monoclinic, space group P21, a=11.046(2), b=7.315(1), c=9.737(1) Å, β=101.34(2)° and Z=2. A square-planar coordination around copper consists of α-amino nitrogen and δ-nitrogen atoms in histidine and α-amino nitrogen and α-carboxyl oxygen atoms in serine, the two amino groups being in cis position. The fifth coordination site is occupied by a water molecule, and the carboxyl oxygen atom of serine in the adjacent complex makes a weak bond with copper to complete a distorted octahedron. The chelating scheme and overall crystal structure are the same as those of (l-alaninato)aqua(l-histidinato)copper(II) trihydrate (1). Crystallization water molecules are situated on the fixed positions in the void space surrounded by the columns of the complexes, but the hydroxyl group of serine takes two sites randomly. The common chelating scheme in the present crystal and 1 is in correspondence with the observation that serine and alanine are of moderate cooperativity with histidine in forming the ternary complexes.