Enantiomeric Recognition of α-Aminoacids by a Uranyl Salen-Bis-Porphyrin Complex.

Chiara M A Gangemi,Giuseppe Trusso Sfrazzetto,Ugne Rimkaite,Andrea Pappalardo,Federica Cipria

doi:10.3389/fchem.2019.00836

Abstract

A novel uranyl salen-bis-porphyrin complex, in which two porphyrin subunits and salen moiety were directly linked, was synthesized for the recognition of tetrabutylammonium (TBA) amino acids. This uranyl salen complex, due to the presence of porphyrins with their fluorescence properties, represents the first example of a luminescence of uranyl salen complexes. UV/Vis measurements indicate the formation of 1:1 host–guest complexes, whereas UV-vis and fluorescence studies revealed that this complex acts as a receptor for the enantiomeric recognition of α-aminoacids derivatives, with high association constants and an excellent enantiomeric discrimination between the two enantiomers of phenylalanine–TBA.

Highlights

Salen ligands are a class of molecules that have been widely explored in the field of supramolecular chemistry
Salen ligands rose to prominence thanks to the pioneering work of Jacobsen and Katsuki that paved the way to one of the most well-designed protocol for the enantioselective epoxidation of unfunctionalized alkenes catalyzed by chiral manganese salen complexes (Jacobsen, 1993; Katsuki, 2000; Yoon and Jacobsen, 2003; La Paglia Fragola et al, 2012; Trusso Sfrazzetto et al, 2015; Ballistreri et al, 2016, 2018; Zammataro et al, 2019)
The presence of porphyrin arms lead to a receptor that possesses luminescence properties that are not quenched by the coordination with the uranyl cation, which decreases the fluorescence intensity in uranyl salen complexes

Summary

Introduction

Salen ligands are a class of molecules that have been widely explored in the field of supramolecular chemistry. Chiral uranyl salen complexes have proved to be excellent receptors for amino acid salts (Amato et al, 2007, 2010, 2011; Ballistreri et al, 2010; Pappalardo et al, 2012a), since the uranyl metal center, acting as a Lewis acid, possesses an equatorial fifth position able to coordinate one molecule of carboxylate anion (Ballistreri et al, 2012; Brancatelli et al, 2013) These synthetic enantioselective receptors could help to better understand the mechanisms of drugs action; processes that are involved in immunological responses and processes of the storage of Luminescence Receptor for α-Amino Acids genetic information. Slightly modification of their structures could lead to chemosensors, which due to their simple use, relatively low cost and high sensitivity are significant in the chemical analysis

Methods

Results

Conclusion