Quantitative chirality/enantioselectivity relations in large random supramolecular structures
We study the relationship between shape and enantioselectivity, employing quantitative geometric chirality measurements. The model we use comprises of the boundary surfaces of two-dimensional (2D) chiral, large, random selectors (diffusion limited aggregates), interacting with homologous series of small 2D-chiral S-shaped probes (the selectands). We show how the enantioselectivity of the selectors depends on the chirality of the selectands and report the following findings: I) The enantioselectivity of a chiral selector can switch preference from the "right" to the "left" enantiomer within a homologous series of selectands. II) At this switch point the chiral selector is functionally achiral. III) Within a homologous series of chiral selectands, there is a "resonance of recognition", namely, the classical key-lock concept is replaced by a picture of various degrees of recognition. IV) The degree of enantioselectivity and the switch in handedness preference are the outcome of a complex interplay between the details of the specific geometry of the selector and the selectand, and the global shape parameter of chirality measure. V) It is shown that isochiral selectands, namely selectands of the same chirality value, may be recognized differently by a chiral selector. VI) It is proposed that a more realistic way to treat the issue of minimal points needed for chiral interaction is resolution based. VII) It is shown how to attach handedness to purely random objects.
Katzenelson
O
Institute of Chemistry and the Lise Meitner Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, Israel.
Avnir
D