Design and Synthesis of a Stable Supramolecular Trigonal Prism Formed by the Self-Assembly of a Linear Tetrakis(Zn<sup>2+</sup>−cyclen) Complex and Trianionic Trithiocyanuric Acid in Aqueous Solution and Its Complexation with DNA (Cyclen = 1,4,7,10-Tetraazacyclododecane)

A new supramolecular complex, {(Zn<sub>4</sub>L<sup>4</sup>)<sub>3</sub>−(TCA<sup>3−</sup>)<sub>4</sub>}<sup>12+</sup>, was designed and synthesized by the 3:4 self-assembly of a linear tetrakis(Zn<sup>2+</sup>−cyclen) complex (Zn<sub>4</sub>L<sup>4</sup>)<sup>8+</sup> and trianionic trithiocyanurate (TCA<sup>3−</sup>) in aqueous solution (cyclen = 1,4,7,10-tetraazacyclododecane). The {(Zn<sub>4</sub>L<sup>4</sup>)<sub>3</sub>−(TCA<sup>3−</sup>)<sub>4</sub>}<sup>12+</sup> 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 <sup>1</sup>H NMR titration, potentiometric pH and UV titrations, and MS measurements. The complex does not dissociate into the starting building blocks in the presence of Zn<sup>2+</sup>-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.