Spectroscopic and potentiometric studies of the interaction of adenine with trivalent metal ions

Potentiometric titration was used to determine the potentiometric diagrams of complexes of adenine with Al3+, Cr3+, and Fe3+. IR and Raman spectra of solids show that the interaction of adenine with Cr3+ is not as strong as the other metals. Fe3+ binds to adenine at low and medium pH values at an Fe3+-adenine ratio of 6, while Al3+ binds to adenine at all pH values at an Al3+-adenine ratio of 8. The IR band associated with N-9-H is split into two components at high and low wavenumbers; IR band splitting has been observed for groups with a large dipole moment such as carbonyl and phosphate. To the best of our knowledge, this is the first time to see the splitting of IR bands involving a nitrogen. We also obtained potentiometric titration plots for adenine with Al3+, Cr3+, and Fe3+, independently, in various molar ratios which showed an interaction with adenine, consistent with the IR and Raman findings. Metal-adenine-hydroxo complexes were formed.