N9,N9′-polymethylene-bisadenine complexes with d10 metal ions

The reaction of N9,N9′-(tri or tetramethylene)-bisadenines (Ade2Cx; x = 3 or 4) in HCl 2 M at 50 °C with MCl2 · 2H2O [M = Zn(II), Cd(II)] yields outer sphere compounds like the previously described [(H-Ade)2C3][ZnCl4] · H2O (3) and [(H-Ade)2C3]2[Cd2Cl8(H2O)2] · 4H2O (4) for Ade2C3 and the new {[(H-Ade)2C4][Cd2Cl6(H2O)2] · 2H2O}n (5) for Ade2C4. On the other hand, only in case of Zn(II) complexes by changing [HCl] to 0.1 M, the inner sphere compounds [H-(Ade)2C3(ZnCl3)] (6) and [H-(Ade)2C4(ZnCl3)] · 1.5H2O (7) are obtained. X-ray diffraction study of compound 6, which represents the first inner sphere complex with a N9,N9′-bisadenine, shows a zwitterionic form with one adenine ring protonated at N(1) while the other ring is coordinated via N(7) to a ZnCl3 moiety as in other alkyl-adenine derivatives. In addition, with Ade2C4, is also possible to obtain another inner sphere complex: [(H-Ade)2C4(ZnCl3)2] · 3H2O (8).

The general behaviour of (tri and tetramethylene)-bisadenines with Zn(II) and Cd(II) in acidic media has been studied. The Cd(II) ion only yields outer sphere complexes with N9,N9′-polymethylene-bisadenines in acidic media. By a modification of the reaction conditions, it is possible to isolate the equivalent inner sphere complexes for both ligands: [H-(Ade)2Cx(ZnCl3)] (x = 3, 4).Figure optionsDownload as PowerPoint slide