Crystal and molecular structure of the ternary complex Zn(II)–ATP–2,2′-bipyridyl

A series of microcrystalline compounds between adenosine 5′-triphosphoric acid (ATP), 22′-bipyridyl and some 3d metal ions, such as Mn(II), Co(II), Cu(II) and Zn(II), have been obtained in 1:1 ratio [1]. Crystal suitable for X-ray analysis were obtained for the zinc compound. Diffractometer data, collected on one of these crystals, gave the following results: a = 11.105(3), b = 25.223(7), c = 1.539(3) Å, β = 91.34(4)°, monoclinic, space group P21. 1617 reflections with intensity greater then twice their standard deviation were used for the structure determination and refinement (R = 0.098). The structure of the compound consists of dimeric molecules in which two zinc atoms are held together by two –OPO– bridges from the γ-phosphate groups of two ATP molecules (Fig. 1). Both zinc atoms show a distorted octahedral coordination, formed by two oxygen atoms from different γ-phosphate groups, one oxygen atom from the β-phosphate group and the two nitrogen atoms of the bipyridyl ligand. The sixth position is completed by an α-phosphate oxygen atom which is only weakly bound. ZnN and ZnO distances average respectively 2.15(4) and 2.0293) Å. The structure is held together by strong intermolecular bipyridyl–purine and bipyridyl–bipyridyl stacking interactions. Weaker bipyridyl–purine intramolecular stacking is also observed. The molecule provides a possible model for ATP transport and phosphate group transfer mechanism.