Structure-cation complexation relationships for ortho-, meta-, and para-substituted bis(oxymethylcrown)benzenes and α,α'-xylenes

David A Babb,Richard A Bartsch,Bronislaw P Czech,Christian V Stevens

doi:10.3998/ark.5550190.0004.c15

Abstract

New bis(crown ether) compounds are synthesized by attaching two (hydroxymethyl)crown ether units to a benzene or α,α'-xylene framework. Bis(15-crown-5) polyether substitution patterns are varied from ortho to meta to para. ortho-Bis(18-crown-6) polyethers are prepared together with mono(crown ether) analogs, as well as ortho-bis(12-crown-4) polyethers. Complexation abilities of these compounds for alkali metal cations are evaluated by picrate extraction allowing the influence of structural modifications in the ligands on extraction constants (Kex) and association constants (Ka) for alkali metal cations to be assessed.

Highlights

In the investigation of crown ether-cation interactions it was determined that crown ethers can form 2:1 “sandwich” complexes with cations that are too large to fit into the macrocyclic cavity.[1,2,3,4,5] This led to the synthesis of new compounds in which two or more crown ether units were covalently linked in a fashion to promote formation of intramolecular 2:1 complexes.[6]
We report the results of a systematic study of structural variations in bis(crown ethers) formed by attaching twocrown ether units to a benzene or α,α’-xylene framework
The influence of these structural variations upon alkali metal cation complexation are assessed by picrate extraction

Summary

Introduction

In the investigation of crown ether-cation interactions it was determined that crown ethers can form 2:1 (host:guest) “sandwich” complexes with cations that are too large to fit into the macrocyclic cavity.[1,2,3,4,5] This led to the synthesis of new compounds in which two or more crown ether units were covalently linked in a fashion to promote formation of intramolecular 2:1 (crown ether:cation) complexes.[6]. We report the results of a systematic study of structural variations in bis(crown ethers) formed by attaching two (hydroxymethyl)crown ether units to a benzene or α,α’-xylene framework. The influence of these structural variations (crown ether ring size and length of the spacer between the crown ether ring and the central benzene ring) upon alkali metal cation complexation are assessed by picrate extraction

Methods

Results

Conclusion