Sorting Phenomena and Chirality Transfer in Fluoride-Bridged Macrocyclic Rare Earth Complexes.

Trevor A. Cabreros,Jerzy Lisowski,Katarzyna Ślepokura,Gilles Muller

doi:10.1021/acs.inorgchem.1c03034

Trevor A. Cabreros, Jerzy Lisowski + Show 2 more

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https://doi.org/10.1021/acs.inorgchem.1c03034

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Abstract

The reaction of fluoride anions with mononuclear lanthanide(III) and yttrium(III) hexaaza-macrocyclic complexes results in the formation of dinuclear fluoride-bridged complexes. As indicated by X-ray crystal structures, in these complexes two metal ions bound by the macrocycles are linked by two or three bridging fluoride anions, depending on the type of the macrocycle. In the case of the chiral hexaaza-macrocycle L1 derived from trans-1,2-diaminocyclohexane, the formation of these μ2-fluorido dinuclear complexes is accompanied by enantiomeric self-recognition of macrocyclic units. In contrast, this kind of recognition is not observed in the case of complexes of the chiral macrocycle L2 derived from 1,2-diphenylethylenediamine. The reaction of fluoride with a mixture of mononuclear complexes of L1 and L2, containing two different Ln(III) ions, results in narcissistic sorting of macrocyclic units. Conversely, a similar reaction involving mononuclear complexes of L1 and complexes of achiral macrocycle L3 based on ethylenediamine results in sociable sorting of macrocyclic units and preferable formation of heterodinuclear complexes. In addition, formation of these heterodinuclear complexes is accompanied by chirality transfer from the chiral macrocycle L1 to the achiral macrocycle L3 as indicated by CPL and CD spectra.

Highlights

Chiral structures and chiral recognition phenomena are fundamental features of molecular biological systems, and chirality is a central issue in various areas of organic and inorganic chemistry
Ln(III) complexes with cyclen-based tetraaza-marocycles where dimers are linked by single fluoride anions or mononuclear complexes with terminal fluoride are generated in reactions with fluoride salts
This difference reflects more open axial coordination spheres of the complexes of hexaazamacrocycles. Within these dimeric complexes the macrocyclic units L1−L3 are in a relatively close contact, and the steric interactions between them leads to sorting phenomena

Summary

Introduction

Chiral structures and chiral recognition phenomena are fundamental features of molecular biological systems, and chirality is a central issue in various areas of organic and inorganic chemistry. Chiral sorting corresponds to enantiomeric self-recognition or enantiomeric self-discrimination, and these processes have been documented for supramolecular systems,[1−6] metal complexes,[7−21] and organic systems, including macrocyclic compounds.[22−31] Chiral sorting phenomena are most often demonstrated for solid state, while examples of enantiomeric self-recognition well documented for solutions of metal complexes are less common Another important issue in the synthesis of elaborate enantiopure metal complexes or supramolecular assemblies is chirality transfer,[32−43] e.g., the transmission of chiral information from enantiopure ligands to metal centers. For similar reasons recognition and self-sorting phenomena[4,6−12,20,21] in lanthanide systems are not so well explored in comparison with the systems based on stable organic compounds or more rigid and inert transition metal complexes

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