Chemistry

Stacked Platinum

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Science  02 Jul 2010:
Vol. 329, Issue 5987, pp. 15
DOI: 10.1126/science.329.5987.15-b
CREDIT: MARK MACLACHLAN

Platinum is a remarkably versatile chemical catalyst. Recently, chemists have also begun to direct its coordination properties toward the assembly of complex supramolecular structures. Frischmann et al. constructed a family of tunable Schiff base proligands that were designed to self-assemble in head-to-tail fashion when coordinated to Pt2+. The proligands—substituted salicylaldimines—could be generated in situ or before metalation. Puckered Pt4 macrocycles formed that would then stack in either single or alternating configurations, depending on the bulkiness of the peripheral R group, with the latter dominant as the R group increased in size. The authors were surprised to find that when R was 2-hexyldecyl, the columnar macrocycles formed lyotropic liquid crystalline phases when concentrated in nonpolar organic solvents. The complexes showed poor solubility in cyclohexanone, but when cast from a solution using this solvent, they formed parallel columns that were spaced 4 nm apart and extended for hundreds of nanometers. These arrays thus offer a method to access nanotubes with stacked columns of Pt2+ ions.

J. Am. Chem. Soc. 132, 7668 (2010).

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