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)-(TCA(3-))(4)}(12+), was designed and synthesized by the 3:4 self-assembly of a linear tetrakis(Zn2+-cyclen) complex (Zn4L4)(8+) and trianionic trithiocyanurate (TCA(3-)) in aqueous solution (cyclen = 1,4,7,10-tetraazacyclododecane). The {(Zn4L4)(3)-(TCA(3-))(4)}(12+) complex, which should have a trigonal prism configuration, was found to be very stable in aqueous solution at neutral pH and 25 degrees C, as evidenced by H-1 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.