Chemistry

Crystal Tuning

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Science  31 Mar 2006:
Vol. 311, Issue 5769, pp. 1836-1837
DOI: 10.1126/science.311.5769.1836d

Chemists can rationally tune the extended structure of thin films by choosing the substrate on which the films are grown. However, the growth conditions that yield specific morphologies of three-dimensional crystals are still largely determined by trial and error, without a clear understanding of the factors that promote specific structural outcomes.

Grzesiak et al. sought to influence the structure of a metal organic framework solid by adding insoluble polymers to the crystallization solutions, for the purpose of guiding the nucleation process and thereby producing unusual bulk morphologies. The suspended polymers contained either acidic (methacrylic acid) or basic (4-vinylpyridine) components in varied proportion to a hydrophobic cross-linker (divinylbenzene). In the absence of polymer, two crystal phases were known to form from the Zn2+ and benzenedicarboxylate building blocks. A distinct third phase emerged when predominantly nonpolar polymers were added (>70 % divinylbenzene), and the authors characterized its plate-like structure by powder and single-crystal x-ray diffraction, as well as Raman spectroscopy. This heterogeneous nucleation strategy produced additional phases when the benzenedicarboxylate bridges were functionalized with either Br or NH2 groups. — JSY

Angew. Chem. Int. Ed. 45, 10.1002/anie.200504312 (2006).

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