Abstract
A zinc trisporphyrinate has been developed as a chirality sensor for chiral mono-alcohols. In its structure, there are two “spaces” surrounded by three porphyrin moieties, which allow guests to fill in. It has shown extremely high CD sensitivity for a chiral mono-alcohol with a naphthyl substituent, 1-(1-naphthyl)ethanol, at μM level, which is at least three orders of magnitude lower concentration than previous reports. A crystallographic study of the host-guest complex reveals the binding of 1-(1-naphthyl)ethanol to the zinc trisporphyrinate is greatly enhanced by multipoint interactions, such as coordination interactions, hydrogen bonding, π-π and CH···π interactions etc. Spectroscopic studies suggest the corresponding binding constant K1 is over 105 M−1, which is two or three orders of magnitude larger than other mono-alcohols. Among porphyrin systems, this trisporphyrin have the strongest binding affinity for 1-(1-naphthyl)ethanol, which leads to the highest CD sensitivity.
Highlights
Chiral alcohols are commonly encountered structural elements in pharmaceutical drugs, biologically active natural products and synthetic intermediate[1,2,3]
The short ethane-bridge causes the steric interactions between the 3,7-ethyl groups of the porphyrin and the substituents of the ligand, resulting in the induced supramolecular chirality[12]. Another more sensitive system is an ester-linked bisporphyrin developed by Takanami et al, which improves the detecting concentration of mono-alcohols to mM level through the simultaneous double coordination of the hydroxyl group to the two metals[14]
The above studies suggest that this zinc trisporphyrinate has the strongest binding affinity to 1-(1-naphthyl) ethanol and the host-guest complex has the largest CD magnitude per unit, which leads to the highest CD sensitivity
Summary
The magnitude of CD signals relies on the following two factors: 1) The binding affinity of guests to hosts It determines the amount of host-guest complexes formed at low concentrations. The high binding constants for the guest 2 suggest that more host-guest complexes are formed than other mono-alcohols when their concentrations of guests (and hosts) are the same. The above studies suggest that this zinc trisporphyrinate has the strongest binding affinity to 1-(1-naphthyl) ethanol and the host-guest complex has the largest CD magnitude per unit, which leads to the highest CD sensitivity. If we consider the binding constants for 1-(1-naphthyl)ethanol is over 100 times larger than others and its CD contribution per unit is only a few times than others, the major factor causing the highest CD sensitivity for the guest 2 should be the strong bonding affinity, which is due to the strong host-guest interactions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
