Binaphthyl-Based Macrocycles as Optical Sensors for Aromatic Diphenols.

Stefano Piacentini,Marco Caricato,Andrea Nitti,Dario Pasini,Aurora Pacini

doi:10.3390/molecules25030514

Abstract

The synthesis of several rigid, homochiral organic macrocycles possessing, respectively, average molecular D2 and D3 symmetries, is described. They have been obtained from aromatic dicarboxylic acids, in combination with an axially-chiral, suitable dibenzylic alcohol, derived from 1,1′-binaphthyl-2,2′-diol (BINOL) using one-pot esterification reactions in good isolated yields. NMR and circular dichroism (CD) spectroscopies detect the structural and shape variability in the scaffolds, reflected both in terms of the changes in chemical shifts and the shape of selected proton resonances, and in terms of the variation of the CD signature related to the dihedral angle defined by the binaphthyl units embedded in the rigid cyclic skeleton. The D2 cyclic adducts are able to form stable complexes with aromatic diphenols, with binding strengths that are dependent on small variations in the spacing units, and therefore on the shapes of the internal cavities of the cyclic structures.

Highlights

Large, shape-persistent macrocyclic structures are of increasing interest for applications in the field of supramolecular chemistry, molecular recognition, and nanoscience [1,2,3,4]
circular dichroism (CD) spectroscopy can offer better levels of detection when compared with optical spectroscopies and electrochemistry-based methods, and it is frequently used in biosensing, where high sensitivities are required [12,13]
We report on synthesis of novel macrocycles, in which the phenolic functionalities of the binaphthyl units are the synthesis of novel macrocycles, in which the phenolic functionalities of the binaphthyl units protected by t-butyloxycarbonyl groups, and on their unexpected binding of π-electron rich aromatic are protected by t-butyloxycarbonyl groups, and on their unexpected binding of π-electron rich diphenols

Summary

Introduction

Shape-persistent macrocyclic structures are of increasing interest for applications in the field of supramolecular chemistry, molecular recognition, and nanoscience [1,2,3,4]. Shape persistency relates to the conformational stability and rigidity of the covalent cyclic structure. Those features are fundamental properties to be sought in order to enhance the recognition/complexation properties toward suitable inclusion guests. This issue is stringent because macrocycles can self-assemble in stable organic nanotubes by supramolecular organization in the third dimension [5,6,7]. Chirality has been exploited in combination with shape-persistent macrocyclic structures both for sensing and recognition, and for the assembly of chiral nanotubes [8]. CD spectroscopy can offer better levels of detection when compared with optical spectroscopies and electrochemistry-based methods, and it is frequently used in biosensing, where high sensitivities are required [12,13]

Methods

Discussion

Conclusion