Chiral Amine Enantiomeric Excess Determination Using Self‐Assembled Octahedral Fe(II)‐Imine Complexes

Abstract

A receptor assembly composed of iron(II) triflate and pyridine-2,6-dicarbaldehyde is used to determine the enantiomeric excess of alpha-chiral primary amines using circular dichroism spectroscopy. The alpha chiral amines condense with the dialdehyde to form a diimine, which forms a 2:1 octahedral complex with iron(II). The enantiomeric excess values of unknown concentrations of alpha-chiral amines were determined by constructing calibration curves for each amine and then measuring the ellipticity at 600nm. This improves our previously reported assay for enantiomeric excess determination of chiral primary amines by further increasing the wavelength at which CD is measured and reducing the absolute error of the assay.

Chiral superstructures from homochiral Zn2+, Co2+, Fe2+‐2,6‐bis (aryl ethylimine)pyridine complexes

“…The asymmetric unit consists in both cases of [ 1 ‐Λ‐(S,S,S,S)‐Co] 2+ and [ 1 ‐∆‐(R,R,R,R)‐Co] 2+ cations and two BF 4 − anions (Table S3). The Co─N distances, Co 2+ ‐N Pyridine = 1.848 to 1.925 Å and Co 2+ ‐N imine = 2.017 to 2.318 Å, indicate that 1 ‐Λ‐(S,S,S,S)‐Co 2+ and 1 ‐∆‐(R,R,R,R)‐Co 2+ are, as expected, low‐spin complexes at 175 K.…”

“…Molecular and supramolecular chirality both may be used as tools to assemble systems into dissymmetric crystalline architectures based on selective chiral packing . Chiral metallosupramolecular complexes are of considerable interest because of their important applications as stereodynamic probes for chiral sensing, for the preparation of chiral catalysts, and for the development of multifunctional materials . In the design and the synthesis of chiral ligands that, upon coordination with metal ions, can induce high stereoselectivity at a supramolecular level, Schiff bases with stereogenic centres in their backbones have been extensively used as powerful tools for the spontaneous generation of chiral superstructures.…”

Model Building Using Linear Free Energy Relationship Parameters–Eliminating Calibration Curves for Optical Analysis of Enantiomeric Excess

“…6,7,31 Circular dichroism (CD) signal that arise upon binding of a chiral analyte are correlated to the sample's ee values through experimentally derived calibration curves. 6,7,31 Circular dichroism (CD) signal that arise upon binding of a chiral analyte are correlated to the sample's ee values through experimentally derived calibration curves.…”

Chirality Sensing With Stereodynamic Biphenolate Zinc Complexes

“…The chiral amplification process and sensing response can then be exploited for qualitative and quantitative stereochemical analysis of the bound substrate. [16][17][18][19][20] Seminal progress with the development of a variety of chiroptical chemosensors and powerful chirality sensing assays that can be used for the determination of the absolute configuration and enantiomeric excess (ee) of many compounds has been made by Berova and Nakanishi, [21][22][23][24] Anslyn, [25][26][27][28][29] Canary, 30, 31 Joyce, 32 and Borhan. The covalent attachment of a chiral amino acid, carboxylic acid, amine, or alcohol was found to effectively disturb the racemic equilibrium of the biphenyl conformations in the probe, thus inducing spontaneous chirality amplification.…”

“…[8][9][10][11][12] Several probe designs with interesting CD reporter units including molecular bevel gears 13,14 and propellers, 15 have been introduced by Gawronski, Katoono, and others. [16][17][18][19][20] Seminal progress with the development of a variety of chiroptical chemosensors and powerful chirality sensing assays that can be used for the determination of the absolute configuration and enantiomeric excess (ee) of many compounds has been made by Berova and Nakanishi, [21][22][23][24] Anslyn, [25][26][27][28][29] Canary, 30,31 Joyce, 32 and Borhan. [33][34][35] To this end, our group has introduced axially chiral salicylaldehydederived receptors that undergo fast substrate binding and subsequent asymmetric transformation of the first kind toward a highly CD-active conformation.…”