Enantioselective Discrimination of Histidine by Means of an Achiral Cubane-Bridged Bis-Porphyrin

Abstract

A Langmuir film of cubane-bridged bisporphyrin (H 2 por-cubane-H 2 por) at the air/water interface was developed and characterized. The floating film was successfully employed for the chiral discrimination between l- and d-histidine. The enantioselective behavior persisted after the deposition of the film on a solid support using the Langmuir–Schaefer method. Distinct absorption and reflection spectra were observed in the presence of l- or d-histidine, revealing that conformational switching was governed by the interaction between H 2 por-cubane-H 2 por and the histidine enantiomer. The mechanism of chiral selection was investigated using an ad hoc modified nulling ellipsometer, indicating the anti-conformation was dominant in the presence of l-histidine, whereas the presence of d-histidine promoted the formation of tweezer conformation.

Proline Enantiomers Discrimination by (L)-Prolinated Porphyrin Derivative Langmuir–Schaefer Films: Proof of Concept for Chiral Sensing Applications

“…Floating films of H 2 PL(-) spread from a dichloromethane solution were characterized at the air-pure water interface of a Langmuir trough by recording the isotherm curves surface pressure vs. area per molecule [23] (Figure 1a). The isotherm curve shows the typical profile of hydrophobic porphyrins spread on water subphase.…”

“…In order to evaluate the possible interactions among H2PL(-) with the two e mers of proline, the Langmuir curves [23] of the H2PL(-) floating layer were record solving L-and D-proline in the aqueous subphase. In detail, the isotherm curves H 2 PL(-) floating film was transferred from the air/water subphase interface using the horizontal variation of the LB method [38]; that is, the LS technique.…”

“…In order to evaluate the possible interactions among H 2 PL(-) with the two enantiomers of proline, the Langmuir curves [23] of the H 2 PL(-) floating layer were recorded dissolving L-and D-proline in the aqueous subphase. In detail, the isotherm curves of the derivative spread from dichloromethane solution were recorded on: (i) pure water subphase, (ii) subphase containing L-proline water solution (10 −5 M) and (iii) subphase containing D-proline water solution (10 −5 M).…”

“…Such an induced molecular organization and aggregation/configuration were reported to be fundamental for analytes recognition, making deposition through the LB or LS approach essential to ensure sensor functioning [19]. Moreover, this approach has been also used for the assembly of organized porphyrin-based materials expressing chirality at a supramolecular level [20][21][22] and allowing enantiodiscrimination [23]. The development of stereoselective sensing devices is particularly urgent for environmental and health safety [24,25].…”

Engineering copper plasmonic chirality via ligand-induced dissolution for enantioselective recognition of amino acids

“…Histidine plays an important role in many biological functions like immune responses and is present in the active site of many metallozymes. 41,42 The signicance of histidine extends beyond biological functions. It has proven useful in asymmetric synthesis and has been utilized as a catalyst for cross-aldol reactions involving enolizable aldehydes.…”