Chiral Discrimination by a Binuclear Pd Complex Sensor Using ³¹P{¹H} NMR

Abstract

An axially chiral binuclear μ-hydroxo Pd complex (BPHP) first served as an excellent chiral sensor for discriminating a variety of analytes including amino alcohol, amino amide, amino acid, mandelic acid, diol, diamine, and monoamine by 31P­{1H} NMR. A detailed recognition mechanism was proposed based on the single crystal and mass spectrum of Pd-complexes. In general, BPHP sensor, through extracting the acidic hydrogen of an analyte by its Pd–OH group, forms stable diastereomeric complexes with two enantiomers of the analyte giving well distinguishable split 31P­{1H} NMR signals for chiral discrimination.

Chiral Co3Y Propeller-Shaped Chemosensory Platforms Based on19F-NMR

“…The type of sensor–analyte interaction, covalent bond, hydrogen bond, or aromatic interactions is unclear until further evidence is obtained. From previous works, amines are known to coordinate to lanthanide metal centers as well as the recent chiral sensing studies. ,, It is suggestive that the amines will coordinate with the Y III center; however, due to the nature of the ligand with O and NH moieties, hydrogen bonding interactions between the complex and the analyte cannot be excluded.…”

“…Methods incorporating molecules that bear phosphorous atoms are developed to monitor changes with 31 P{ 1 H} NMR due to observable splitting of signals and a broad spectral range compared to 1 H NMR spectra. 15,23 Moreover, the 19 F nucleus of spin quantum number 1/2 has 83% the sensitivity of the 1 H nucleus and is found in 100% natural abundance; with great receptivity, it yields strong signals on an NMR spectrum. 24−31 19 F can also be easily incorporated into organic compounds as it mimics the 1 H nucleus in many environments and benefits from a lack of background interference due to its low natural occurrence; 32,33 thus, it can be used to probe the structure and dynamics of many large and complex biomolecules such as proteins.…”

“…The simultaneous presence of 3d and 4f elements in a single molecule represents an elegant advantage for studying mechanisms and rationalizing experimental data. For example, Y III can be included in this category because it has a size and Lewis acidity similar to Ho III and its diamagnetic character permits monitoring with NMR ( 1 H, 13 C, 15 N, 19 F, or 89 Y). It may also be possible to exchange 3d ions in the same oxidation state without distorting the core topology and permitting monitoring with UV−vis, EPR, or NMR.…”

“…The stereochemical discrimination can occur using spectroscopic methods, including circular dichroism (CD) and fluorescence, − by monitoring absorbance intensity change and NMR, presenting chemically shifted signals for different chiral molecules or complexes. − For the latter, a host–guest complex consisting of a chiral substrate sample interacts with a chiral detector molecule, transferring chiral information and inducing a change in the chiral environment, observed as split signals of precise chemical shifts in the corresponding NMR spectrum. NMR chemosensors for chiral discrimination are typically limited to aromatic-based compounds, facilitating signal splitting by inducing a significant shielding effect.…”

“…Hence, the development of heteronuclear-based sensors represents a reasonable alternative to overcome these hindrances. Methods incorporating molecules that bear phosphorous atoms are developed to monitor changes with 31 P­{ 1 H} NMR due to observable splitting of signals and a broad spectral range compared to 1 H NMR spectra. , Moreover, the 19 F nucleus of spin quantum number 1/2 has 83% the sensitivity of the 1 H nucleus and is found in 100% natural abundance; with great receptivity, it yields strong signals on an NMR spectrum. − 19 F can also be easily incorporated into organic compounds as it mimics the 1 H nucleus in many environments and benefits from a lack of background interference due to its low natural occurrence; , thus, it can be used to probe the structure and dynamics of many large and complex biomolecules such as proteins . The broad detection window of 19 F NMR is conducive to easily distinguishable split signals and narrow overlapping resonances, increasing spectral resolution and providing the simpler deconvolution of complicated spectra.…”