Single-Stranded DNA as Supramolecular Template for One-Dimensional Palladium(II) Arrays

Atomic-level control over the position and growth of a single and continuous metal chain is an ambitious goal that often requires complex and costly processes. Herein, we demonstrate that 1Pd-DNA molecules, comprising a continuous single chain of Pd-II ions, can be prepared by a simple self-assembly reaction between the complex [Pd(Cheld)(CH3CN)] (1Pd_CH3CN) (Cheld=chelidamic acid) and single-stranded DNA homopolymers (ss-DNA) containing adenine (A) or 7-deazaadenine (X) bases. The single Pd-II-base pairs [1Pd(N1-A)] and [1Pd(N1-X)] were synthesized and characterized in solution and solid-state (X-ray diffraction) revealing an arrangement similar to that of natural Watson-Crick base pairs. Subsequently, 1Pd-DNA hybrids were prepared, characterized, and their structures studied by small-angle X-ray scattering (SAXS) and ab-initio calculations. The results indicate that the 1Pd-DNA structures resemble that of double-stranded DNA, with one strand being replaced by a supramolecular stack of continuous Pd-II complexes.