Dartmouth College, Department of Chemistry, Hanover, New Hampshire 03755, USA.
J Am Chem Soc. 2009 Dec 30;131(51):18269-71. doi: 10.1021/ja909149z.
The replacement of one of the carbonyl groups in a 1,2,3-triketone-2-naphthylhydrazone with a pyridine ring yields an original molecular switch that can be switched fully, effectively, and reversibly between the E and Z configurations. This hydrazone-based, pH-controlled, molecular switch is the first example of a chemically controlled configurational rotary switch. The bistable switch exists primarily (97%) as the E configuration in solution and can be converted quantitatively to the Z-H(+) configuration upon treatment with trifluoroacetic acid. When Z-H(+) is passed over a plug of K(2)CO(3), the "metastable" Z configuration is observed using (1)H NMR spectroscopy, which thermally equilibrates to give back the E configuration. The rate of this process is dependent on the polarity of the solvent, indicating that the E/Z isomerization takes place via a rotation around the hydrazone C=N bond.
1,2,3-三酮-2-萘基腙中的一个羰基被吡啶环取代，得到一个原始的分子开关，它可以在 E 和 Z 两种构象之间完全、有效且可逆地切换。这种基于腙的、pH 值控制的分子开关是第一个化学控制的构象旋转开关的例子。双稳态开关主要以 E 构象（在溶液中占 97%）存在，并且可以在与三氟乙酸处理时定量转化为 Z-H(+) 构象。当 Z-H(+) 通过 K(2)CO(3)塞子时，使用 (1)H NMR 光谱观察到“亚稳态”Z 构象，该构象通过热平衡回到 E 构象。这个过程的速率取决于溶剂的极性，表明 E/Z 异构化是通过腙 C=N 键的旋转发生的。
