CONTROL OF ASYMMETRIC SYNTHESIS, SWITCHES AND ROTORS

We start from a racemate (a 50:50 mixture of R and S enantiomers). Then, two tasks can be imagined:

1. to transform a racemate into a pure enantiomer, i.e. convert the "wrong" half into the "good" one.
2. to separate the two enantiomers from the racemate, i.e. excite selectively one of them, breaking the energetic degeneracy.

Our old "toy" model is H2POSH which in the electronic ground state presents a double well potential corresponding to left or right enantiomers depending on the torsional angle of the terminal H around the PS axis. By means of wavepacket propagations we can produce 100% of enantiomeric excess in a sub-ps time scale using a sequence of analytical pulses, either in the IR, or in the UV domain if the electronic excited state is used as intermediate state.

H2POSH has a very low barrier interconnecting R and S enantiomers. To approach more realistic chemical systems, with long racemization times, we are now working with  a chiral olefin, which because of the very high barrier, it has stable enantiomers. There we can separate the R and S enantiomers by using IR+UV laser pulses.

Also exciting is the possibility to interconvert sequentially between the two enantiomers. This constitutes a chiroptical switch. Further, inducing continuous "cis-trans" isomerization, one can construct a molecular rotor.

Wanna know more?

See publication list.