Tailorable Nanoparticles Synthesized

Coordination polymers formed from transition-metal ions and carboxylate-functionalized building blocks are well-known and typically prepared as macroscopic crystalline materials. Chemists at Northwestern University have now found a way of synthesizing the polymers as spherical micro- and nanoparticles (Nature 2005, 438, 651). Moonhyun Oh and Chad A. Mirkin show that addition of an initiation solvent to a precursor solution of metal ions and chiral carboxylate-functionalized binaphthyl bis-metallotridentate Schiff base building blocks results in the spontaneous and fully reversible formation of a new class of nanoparticles consisting of polymerized networks of metal ions and metalloligands such as the network shown (L = ancillary solvent ligand). The nanoparticles aggregate and fuse into uniform, smooth, spherical microparticles that are stable in organic solvents, in water, and in the dried state. The approach opens up the possibility of tuning the chemical and physical properties of the colloidal particles by changing their metal and organic components. “Targeted applications include catalysis, biological labels, encoding materials, and dyes,” Mirkin suggests.