A ZINC(II)-CYCLEN COMPLEX ATTACHED TO AN ANTHRAQUINONE MOIETY THAT ACTS AS A REDOX-ACTIVE NUCLEOBASE RECEPTOR IN AQUEOUS-SOLUTION

Recently, we demonstrated that a zinc(II) macrocyclic tetraamine complex, Zn-II-cyclen (cyclen=1,4,7,10-tetraazacyclododecane), could bind to thymidine (dT) and uridine (U) selectively among the DNA/RNA bases in aqueous solution at physiological pH. This paper describes the design and synthesis of the zinc(II) complex of an anthraquinone-pendant cyclen. The interaction of this complex with a variety of nucleosides has been studied by potentiometric pH titration, H-1 NMR, and a polarographic technique. The effect of the anthraquinone functionality in this complex is an enhanced 1:1 association with N(3)-deprotonated dT (log K=6.6+/-0.1 against 5.6 for Zn-II-cyclen system at 25 degrees C with I=0.10 (NaNO3)) and its congeners, implying an additional anthraquinone-thymine aromatic stacking pi-pi interaction. This complex, moreover, can electrochemically recognize thymidine and other related organic substrates in aqueous solution, and is therefore a new prototype for electrochemical oligonucleotide recognition.