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)

Abstract

A new supramolecular complex, {(Zn(4)L(4))(3)-(TCA(3-))(4)}(12+), was designed and synthesized by the 3:4 self-assembly of a linear tetrakis(Zn(2+)-cyclen) complex (Zn(4)L(4))(8+) and trianionic trithiocyanurate (TCA(3-)) in aqueous solution (cyclen = 1,4,7,10-tetraazacyclododecane). The {(Zn(4)L(4))(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 (1)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(2+)-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.