Chapter 3. Synthetic Receptors for Alkali Metal Cations George W. Gokel* a,b,c and Joseph W. Meisel a,b a Center for Nanoscience, b Department of Chemistry

Chapter 3. Synthetic Receptors for Alkali Metal Cations

George W. Gokel*a,b,c and Joseph W. Meisela,b

aCenter for Nanoscience, bDepartment of Chemistry and Biochemistry, cDepartment of Biology,

University of Missouri-St. Louis, 1 University Blvd.

Saint Louis, MO 63121 USA

*Email: [email protected]

Supplementary information for Synthetic Receptors for Biomolecules: Design Principles and Applications© The Royal Society of Chemistry 2015

Chart 3.1 Solid state structure of the polyether ionophore, monensin A, binding Na+.


Chart 3.2 Partial structures of two biological ion channels showing: (A) Two Na+ binding sites in the LeuT Na+-dependent pump (PDB code 2A65). (B) Four K+ binding sites in the KcsA K+ channel (PDB code 1K4C). (Reproduced with permission from Science 2005, 310, 1461, © American Association for the Advancement of Science)


Figure 3.1 Coordination compounds and bidentate complexes


Figure 3.2 The chemistry leading to the first crown ethers.


Figure 3.3 Solid state structure of dibenzo-18-crown-6 binding K+ (CSD: BEBFAP).


Figure 3.4 Two-armed diaza-18-crown-6 derivatives having three atom sidearms.


Table 3.1 Homogeneous complexation constants and thermodynamic parameters determined in methanola,b.


Figure 3.5 Binding constants determined in 100% methanol solution for 3n-crown-n compounds where n = 4 – 8.


Figure 3.6 Solid state structures of uncomplexed 12-crown-4 (CSD: TOXCDP) and K+ ion complexed by 18-crown-6 (CSD: KTHOXD).


Figure 3.7 Solid state structures of (12C4)2•Na+ (CSD: BEYHES) and ( Aza-12C4)2•Na+ (CSD: FEHDOL).


Figure 3.8 Solvent dependence of 18-crown-6•Na+ binding in methanol and water.


Figure 3.9 Structures of [2.1.1]cryptand and [3.2.2]cryptand.


Figure 3.10 Solid state structure of [2.2.2]cryptand complexing KI.


Figure 3.11 Left: a spherand. Center: a hemispherand. Right a crown-hemispherand.


Figure 3.12 Macrocyclic compounds formed by acid-catalyzed, multiple condensations.


Figure 3.13 Calixarene receptor molecules.


Figure 3.14 K+ complexation by a calix-crown.


Figure 3.15 Comparison of homogeneous binding and extractions constants with transport rate.


Figure 3.16 Schematic representation of a liposome and a typical phospholipid.


Figure 3.17 Redox-switched molecular receptors.


Figure 3.18 Examples of host molecules that can be photo-switched.


Figure 3.19 Relative NH4+ binding strengths for 18-membered ring macrocycles.


Figure 3.20 Crown ether-derived colorimetric sensors: “chromoionophores”.


Figure 3.21 Fluoroionophores based on crown ethers and calixarenes.


Figure 3.22 Chemical structure of the cyclic peptide K+ carrier valinomycin.


Figure 3.23 (Top) Single-armed carbon-pivot and nitrogen pivot lariat ethers. (Bottom) a two-armed or bibracchial nitrogen-pivot lariat ether.


Figure 3.24 Solid state structure of 4,13-diaza-18-crown-6 having two methoxyethyl side arms attached to nitrogen and binding KI.


Table 2 Sodium and potassium cation binding by lariat ethers expressed as log10 KS.a


Figure 3.25 Bibracchial lariat ethers containing π-donor side arms.


Figure 3.26 Solid state structures of phenyl (CSD: OCABEZ) and pentafluorobenzyl (CSD: OCACIE) side-armed bibracchial lariat ethers binding KI.


Figure 3.27 Solid state structure of a calixarene•2Cs+ complex (CSD: RADBUT).


Figure 3.28 A ditopic receptor binding both Na+ and I- (CSD: IBUKUM).


Figure 3.29 An ion-conducting channel based on the cyclodextrin scaffold.


Figure 3.30 Channel designs reported by Lehn (left) and by Fyles and their coworkers.


Figure 3.31 The hydraphile channel concept.


Figure 3.32 An array of synthetic amphiphiles that show channel-like function.


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Chapter 3. Synthetic Receptors for Alkali Metal Cations George W. Gokel* a,b,c and Joseph W. Meisel a,b a Center for Nanoscience, b Department of Chemistry