Absolute configuration and host-guest binding of chiral porphyrin-cages by a combined chiroptical and theoretical approach

Abstract

Porphyrin cage-compounds are used as biomimetic models and substrate-selective catalysts in supramolecular chemistry. In this work we present the resolution of planar-chiral porphyrin cages and the determination of their absolute configuration by vibrational circular dichroism in combination with density functional theory calculations. The chiral porphyrin-cages form complexes with achiral and chiral viologen-guests and upon binding one of the axial enantiomorphs of the guest is bound selectively, as is indicated by induced-electronic-dichroism-spectra in combination with calculations. This host-guest binding also leads to unusual enhanced vibrational circular dichroism, which is the result of a combination of phenomena, such as rigidification of the host and guest structures, charge transfer, and coupling of specific vibration modes of the host and guest. The results offer insights in how the porphyrin cage-compounds may be used to construct a future molecular Turing machine that can write chiral information onto polymer chains.

Endowing Phosphor Materials with Long‐Afterglow Circularly Polarized Phosphorescence via Ball Milling

“…[ 7 ] In order to construct CPL active materials, the combination of luminophore and chiral species is generally adopted. [ 8 ] The linkage between the luminophore and chiral species can be either covalent bond or noncovalent bond. [ 9 ] Such construction concept provides an opportunity to construct vast organic CPL materials and many commercially available luminescent dyes have been fabricated into CPL active materials.…”

Enantioselective synthesis of chiral porphyrin macrocyclic hosts and kinetic enantiorecognition of viologen guests

“…In earlier work, we reported on the post-modification of the achiral porphyrin cage H21 20 by providing it with a nitro function, yielding a racemic mixture of planar chiral nitro-functionalized porphyrin cage H22 . 21 The enantiomers of H22 could be resolved by chiral HPLC 22 and by installing a chiral auxiliary on the corresponding amino-functionalized host. 23 The enantiopure hosts investigated earlier were shown to have small differences in affinity for chiral viologen guests (up to 3-fold difference in binding constant K assoc ).…”

“… 23 The enantiopure hosts investigated earlier were shown to have small differences in affinity for chiral viologen guests (up to 3-fold difference in binding constant K assoc ). 22,23 In this paper we report an alternative approach to synthesize a chiral C 2 -symmetric porphyrin cage compound, i.e. a host in which the porphyrin macrocycle is linked to the glycoluril framework via chiral linkers ( H23 , Fig.…”

Allosteric Guest Binding in Chiral Zirconium(IV) Double Decker Porphyrin Cages

“…Red traces (+)‐Zr(1) 2 , blue traces (−)‐Zr(1) 2 ; c=0.15–0.18 mM in CD 2 Cl 2 . (C) IR and (D) VCD spectra of the two enantiomers of Zr(1) 2 (solid traces) overlaid with the spectra [63] of the two enantiomers of porphyrin cage H 2 3 (dotted traces).…”

“…Strikingly, these sandwich complexes display VCD fingerprints that are very similar to the recently reported single porphyrin cage compound H 2 3 (Figure 1), in which the chirality was introduced into the molecule in a completely different manner, i. e . by substituting each of the xylylene side‐walls with a nitro‐group [63] . The VCD spectra of (+)‐Zr(1) 2 and S p ‐( R , R )‐ H 2 3 both exhibit four characteristic positive bands at 1253, 1285, 1330/1336 and 1375 cm −1 , and a negative‐to‐positive couplet at 1705–1728 cm −1 (Figure 8C−D) and are rather intense (dissymmetry factors g abs around 1.2×10 −1 ).…”