Solution studies on trace metal ion interactions with adenine as primary ligand and 5-halouracils as secondary ligands

The interaction of trace metal ions, viz. Mn-II, Co-II, Ni-II, Cu-II, Zn-II and Cd-II with adenine (A) as primary ligand and 5-halouracils, viz. 5-bro mouracil (5BrU) and 5-iodouracil (5IU) as secondary ligands (L) has been st udied at 25 +/- 0.1 degrees C and at constant ionic strength (mu = 0.1 M Na NO3), in an aqueous medium using Bjerrum-Calvin's pH-titration technique as adopted by Irving and Rossotti for binary (ML), and by Chidambaram and Bha ttacharya for ternary (MAL) systems respectively. The experimental pH-titra tion data were analyzed with the aid of the BEST computer program in order to evaluate formation constants of various intermediate complex species for med in binary and ternary systems involving nucleobases (viz. A, 5BrU and 5 IU). The relative stability of each ternary complex was compared with that of the corresponding binary complexes in terms of Delta log K values.