Design and Synthesis of a Stable Supramolecular Trigonal Prism Formed by the Self-Assembly of a Linear Tetrakis(Zn2+-cyclen) Complex and Trianionic Trithiocyanuric Acid in Aqueous Solution and Its Complexation with DNA (Cyclen =1,4,7,10-Tetraazacyclododecane)

A new supramolecular complex, {(Zn4L4)3−(TCA3−)4}12+, was designed and synthesized by the 3:4 self-assembly of a linear tetrakis(Zn2+−cyclen) complex (Zn4L4)8+ and trianionic trithiocyanurate (TCA3−) in aqueous solution (cyclen = 1,4,7,10-tetraazacyclododecane). The {(Zn4L4)3−(TCA3−)4}12+ complex, which should have a trigonal prism configuration, was found to be very stable in aqueous solution at neutral pH and 25 °C, as evidenced by 1H NMR titration, potentiometric pH and UV titrations, and MS measurements. The complex does not dissociate into the starting building blocks in the presence of Zn2+-binding anions such as phosphates and double-stranded DNA. The results of the competitive binding assays with ethidium bromide and calf-thymus DNA, thermal melting experiments, gel mobility shift assays, and dynamic light-scattering data strongly indicated that the trigonal prism functions as a polycationic template to induce the aggregation of double-stranded DNA.