Interaction of metal ions with the antihyperuricemic drug allopurinol (H2L): synthesis and crystal structure of dimeric [Zn2(µ-HL)2Cl2(H2O)2]

Abstract

The complex Zn^II(HL)Cl(H₂O)(H₂L = allopurinol = 1,5-dihydropyrazolo[3,4-d]pyrimidin-4-one) has been crystallized from aqueous solution. Crystal data: triclinic, space group P1^–(no. 2), a= 7.052(2), b= 7.726(2), c= 8.341(4)Å, α= 69.78(3), β= 87.75(3), γ= 68.27(3)° and Z= 2. The complex exhibits a new centrosymmetric dimeric structure of the type [Zn₂(µ-HL)₂Cl₂(H₂O)₂]. Two zinc ions with an intramolecular metal-to-metal distance of 3.713(2)Å are bridged by two N(8)–N(9)-chelating anionic allopurinol ligands. The dimeric complex units are stabilized by an extended network of hydrogen bonding contacts. The co-ordinating allopurinol rings are stacked with a mean spacing distance of 3.39 Å. A review of the co-ordinating properties of neutral, anionic and cationic allopurinol including recent crystallographic data is given.