Chemistry

A Golden Chair

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Science  15 Jun 2001:
Vol. 292, Issue 5524, pp. 1967-1969
DOI: 10.1126/science.292.5524.1967f

Inorganic molecules with intricate structures can be assembled from metal centers and multidentate ligands, with the latter forming two or more bonds to the metal. Cyclic compounds of this kind, termed metallacycles, may find applications as catalysts, sensors, and molecular electronic components. Unlike many organic cyclic molecules, metallacycles usually are rigid.

Yip and Prabhavathy have synthesized a metallacycle that has a structure and fluxionality reminiscent of cyclohexane. The molecular ring consists of three gold atoms and three bridging bidentate ligands (9,10-bis[diphenylphosphino]anthracene) with an overall diameter of about 1 nm and a chair conformation similar to that adopted by cyclohexane. Solution 31P and 1H nuclear magnetic resonance (NMR) spectra show that the ring is stable for several days and indicate that the ring converts between two conformations in which all of the phosphorus atoms but not all of the protons experience identical chemical environments. The authors conclude that a ring inversion occurs, and this interpretation is supported by two-dimensional NMR data, which show that a slow conversion occurs at 228 K. Hence, this fluorescent (475 nm) molecule mimics the structural and dynamic features of cyclohexane. — JU

Angew. Chem. Int. Ed.40, 2159 (2001).

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