Polyoxometalates Macroanions: From Self-Recognition to Functional Materials.

摘要

Large, hydrophilic polyoxoanions with high solubility in water and/or other polar solvents demonstrate unique solution behavior by self-assembling into single layer, hollow, spherical "blackberry"-like structures, which are obviously different from small, simple ions. These macroions cannot be treated as insoluble colloidal suspensions either because they form stable "real solutions". These inorganic macroions demonstrate some features usually Pobelieved to belong only to complex biological molecules, such as the self-recognition, chiral recognition, and chiral selection in dilute solutions. Highly negatively-charged molecular rods with almost identical structures were observed to self-assemble into their individual 'blackberry' structures, demonstrating tiny differences (e.g. charge, charge distribution, and organic ligands) could lead to self-recognition behavior. Chiral recognition behavior was understood by studying the self-assembly process in the racemic mixture solutions. Moreover, chiral organic molecules (lactic acid and tartaric acid) can be used to selectively inhibit the self-assembly process of one of the enantiomers. Meanwhile, polyoxometalate-based organic-inorganic hybrid materials demonstrate amphiphilic properties by self-assembling into vesicles and reverse vesicles in polar and non-polar solvents, respectively, and form catalytic emulsions in biphasic environments. Designed hybrid molecules can be programed to different devices with applications in fluorescence, photo-electronic conversion, molecular switch, and catalyst.