HGCL2 COORDINATION TO GUANINE DERIVATIVES - STRUCTURAL AND SPECTROSCOPIC STUDIES ON THE INTERACTIONS WITH 9-ETHYLGUANINE, 1,9-DIMETHYLGUANINE AND 2-AMINO-6-METHOXY-9-METHYLPURINE (6,9-DIMETHYLGUANINE)

The coordination of HgCl2 to 9-ethylguanine, 1,9-dimethylguanine and 2 -amino-6-methoxy-9-methylpurine (6,9-dimethylguanine) has been studied . The X-ray structures of the complexes HgCl2 (2-amino-6-methoxy-9-met hylpurine-N7) (1) (monoclinic, P2(1)/m, a=10.160(3), b=6.222(1), c=11. 060(3) angstrom, beta=116.11(2)-degrees, Z=2) and {[HgCl2.(1,9-dimethy l-guanine-N7)]2HgCl2}n (2) (orthorhombic, Pbca, a=6.955(2), b=17.176(6 ), c=21.829(9) angstrom, Z=4) are reported. Binding of HgCl2 is throug h N7 of the purine bases. In 1 discrete molecules are formed, while 2 is a linear polymer with (Hg-Cl)n chains to which the guanine bases an d chloro ligands are coordinated. The solution behavior is characteriz ed by a rapid ligand exchange and low complex formation constants, log beta1=0.4 (1), 1.3 (1:1 adduct of 2) and 1.0 [HgCl2.9-EtGH] (3).