Stationary-Phase Complexation of Crown Ethers with Polyammonium Ions Chemically Bonded on Polymer Resin

Abstract

Crown ether complexation has received much attention, though more than three decades have passed since this class of compounds was first synthesized by Pedersen.1 One typical question in crown-ether chemistry is how the selectivity in crown ether complexation emerges. Understanding the origin of the selectivity in crown-ether complexation is not only of fundamental interest, but also of practical importance. Various thermodynamic 2-4 , structural [5][6][7][8] , and computational research efforts 9,10 have been conducted to answer this question. The size-fit theory was a widely accepted concept to explain crown-ether complexation selectivity, and is still regarded as a dominant factor in some instances. However, there are a number of examples in which the selectivity does not follow simple size-fit theories. 11Thus, it is reasonable to regard size-fit as one of the important factors governing crown ether complexation selectivity.Crown ether complexation with simple metal cations has been most extensively studied, because simple inorganic cations are well characterized; thus, a number of reliable physicochemical data are available, which allow us to quantitatively discuss the thermodynamic and structural aspects of crown ether complexes. This background in fundamental chemistry has allowed us to develop a variety of analytical methods based on crown ether complexation. Crown ethers have been utilized for separation [12][13][14] , ion selective electrodes 15,16 , and optical sensors 17,18 for simple inorganic cations (mainly metal cations). In contrast, studies on the complexation of crown ethers with organic cations have been relatively few. However, this does not necessarily mean that organic cations are less important than inorganic cations in crown ether chemistry; on the contrary, complexation with organic cations including the conjugate acids of amines and aminoacids is expected to become more important in biological, biochemical, medical, and pharmaceutical sciences.For investigating polyether complexation, we have developed efficient means based on separation techniques, such as cation-exchange chromatography 19-22 , anion-exchange chromatography 23,24 , and capillary electrophoresis. 25 These methods have permitted us to elucidate polyether chemistry, which is difficult to study with conventional spectrometric, electrochemical, and thermodynamic methods. In the present work, we chromatographically studied the complexation behaviors of crown ethers with polyammonium ions anchored on a polymer resin. The purposes of this work were (1) to characterize the retention of crown ethers in these stationary phases, (2) to elucidate the phenomena which take place in or on the stationary phases, and (3) to show that the stationary phases are useful to study polyether complexation. The complexation of crown ethers with polyammonium ions has not been investigated very well, even in solution. Thus, the present method is expected to elucidate important aspects of crown ether complexation with polyammonium ions. Experiment...

Fluorescence color change of supramolecular polymer networks controlled by crown ether‐cation recognition

“…Polymer P1 contains ammonium cations in the side chain and was thus chosen as target for M1 . Based on the host‐guest recognition of B15C5 and ammonium ions, [48] the SPNs can be formed by mixing M1 and P1 . Due to the presence of the quinoline group, host M1 exhibits blue fluorescence.…”

Development of Chemically Bonded Crown Ether Stationary Phases in Capillary Ion Chromatography

“…Macrocyclic ligands such as crown ethers and cryptands are highly selective in binding metal and other cations and have been employed in a variety of separation technologies, including solvent extraction, membranes and chromatography based on the size-fit theory as one of the important factors overseeing the complexation selectivity [2][3][4][5][6]. Crown ether complexation with simple metal cations has been most extensively studied and a number of reliable physicochemical data are available, thus allowing us to quantitatively discuss the thermodynamic and structural aspects of crown ether complexes [7][8].…”