A pH activated configurational rotary switch: controlling the E/Z isomerization in hydrazones.
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.
Landge
Shainaz M
SM
Dartmouth College, Department of Chemistry, Hanover, New Hampshire 03755, USA.
Aprahamian
Ivan
I
D006835:Hydrazones / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D011725:Pyridines; D012997:Solvents; D013237:Stereoisomerism; D013696:Temperature
D006835:Hydrazones; D011725:Pyridines; D012997:Solvents