Chiral Host
Enantiomers being mirror images to each other are difficult to distinguish using simple chemical reaction. Yet L-linalool in coriander leaves and D-linalool in lavender smell differently. In case of antidepressant drug methylphenidate, one enantiomer is 13 times more potent that the other. These are only two representative examples showing the discrimination between enantiomers possible in nature. The quest for guest molecules capable of discriminating enantiomers are not new but until recently chiral recognition mechanism was largely based on molecular simulations as no structurally characterized host-guest complexes existed. Recently we were able to show three point chiral recognition in a set of structurally characterized host-guest adduct for the first time (chiral separation 93% - 100% ee). Thus we arrived at an elegant solution of a long time pending problem using simple chiral amino acid derivatives and metal ions. To reach this stage we had to develop the coordination chemistry first, which lead to quite a few interesting observations important in the areas of supra molecular chemistry, coordination cages and channels (Figure 1).
Figure 1. Highlights of our findings in chiral recognition (above) and metallocavities.
Recognition of chiral amino alcohol Chemistry A European Journal, 2010, 16, 5004
Recognition of chiral amine Crystal Growth & Design, 2014, 14, 3958.
Factors responsible for recognition in chiral amine Inorganica Chimica Acta, 2019, 486, 387
Recognition of chiral amine using a different approach Inorganica Chimica Acta, 2020, 502, accepted
Functional Polymer
We may have found the way to recognize enantiomers but to reach a stage where these can be used in a practical product we think we need to bound these to solid support. Thus along with the coordination chemistry we have started exploring polymers with functional groups which we can functionalize to our requirement. One problem with the polymers we often encounter is the characterization in the molecular level. Thus at present we are dabbling with both aniline based polymers as well as oligomers. These explorations generated quite a few seemingly unrelated interesting results (Figure 2) which we expect to converge eventually to our original goal of having practical chiral selector and sensor with in-depth molecular understanding.
Figure 2. Highlights of our findings in applied polymer science and organic transformation.
Polymer synthesis & Chromium removal Journal of Hazardous Materials, 2007, 143, 24.
A different polymer where metal recovery is possible Chemical Engineering Journal, 2008, 141, 130.
Controlling polymer architecture with solvents Journal of Applied polymer Science, 2008, 1158.
New architecturally redesigned polymer with improved removal Chemical Engineering Journal, 2018, 350, 599.