SELF-RECOGNITION IN HELICATE SELF-ASSEMBLY - SPONTANEOUS FORMATION OFHELICAL METAL-COMPLEXES FROM MIXTURES OF LIGANDS AND METAL-IONS

On treatment with copper(I) ions, mixtures of the [oligo(2,2')-bipyrid ine] strands 2-5 yield spontaneously the double helicates 2H(2)-2H(5) without significant crossover. Similarly, when a mixture of the two tr is-bypyridine ligands 1 and 3a (containing different substitutions) is allowed to react with copper(I) and nickel(II) ions, only the double helicate 2H(3a) and the triple helicate 3H(1) are formed. Thus, these systems undergo self-assembly of helicates with self-recognition. The process represents a self/nonself-discrimination involving the prefere ntial binding of like metal ions by like ligand strands in a mixture t o selectively assemble into the corresponding helicates. In a broader perspective, these results point to a change in paradigm from pure com pounds to instructed mixtures-that is from seeking chemical purity to designing programmed systems composed of mixtures of instructed compon ents capable of spontaneously forming well-defined superstructures thr ough self-processes.