Supramolecular dendrimer chemistry: using dendritic crown ethers to reversibly generate functional assemblies

TY - JOUR

T1 - Supramolecular dendrimer chemistry: using dendritic crown ethers to reversibly generate functional assemblies

AU - Dykes, G M

AU - Smith, D K

PY - 2003/5/26

Y1 - 2003/5/26

N2 - A series of crown ether derivatives functionalised with dendritic branching based on L-lysine repeat units has been synthesised. The ability of these receptors to interact with cationic guests has been investigated using NMR and mass spectrometric techniques. Binding constants have been evaluated, some using competitive binding assays, and these indicate that the strength of interaction between the encapsulated crown-ether and cationic guests decreases with increasing dendritic functionalisation. The interaction of these dendritic branches with ditopic ammonium cation functionalised templates has been investigated, and Job plot analysis indicates the formation of 2:1 (branch/template) stoichiometric complexes in MeOH solution. These supramolecular assemblies have been disassembled by the addition of potassium cations. hence achieving controlled release of the template back into solution. This process has been investigated by NMR methods and the effect of counteranion on these studies is reported. The use of ditopic ammonium cations possessing long alkyl spacer chains as templates has also been investigated, and in this case, the 2:1 assembly that forms, goes on to achieve higher order levels of organisation, hence gelating the solvent. This particular system is therefore a rare example in which discrete, characterisable dendritic supermolecules possess an inherent potential for further supramolecular assembly, to yield new materials. (C) 2003 Elsevier Science Ltd. All rights reserved.

AB - A series of crown ether derivatives functionalised with dendritic branching based on L-lysine repeat units has been synthesised. The ability of these receptors to interact with cationic guests has been investigated using NMR and mass spectrometric techniques. Binding constants have been evaluated, some using competitive binding assays, and these indicate that the strength of interaction between the encapsulated crown-ether and cationic guests decreases with increasing dendritic functionalisation. The interaction of these dendritic branches with ditopic ammonium cation functionalised templates has been investigated, and Job plot analysis indicates the formation of 2:1 (branch/template) stoichiometric complexes in MeOH solution. These supramolecular assemblies have been disassembled by the addition of potassium cations. hence achieving controlled release of the template back into solution. This process has been investigated by NMR methods and the effect of counteranion on these studies is reported. The use of ditopic ammonium cations possessing long alkyl spacer chains as templates has also been investigated, and in this case, the 2:1 assembly that forms, goes on to achieve higher order levels of organisation, hence gelating the solvent. This particular system is therefore a rare example in which discrete, characterisable dendritic supermolecules possess an inherent potential for further supramolecular assembly, to yield new materials. (C) 2003 Elsevier Science Ltd. All rights reserved.

KW - crown ethers

KW - dendrimers

KW - gels

KW - supramolecular chemistry

KW - self assembly

KW - POLY(PROPYLENE IMINE) DENDRIMERS

KW - NUCLEIC-ACID DENDRIMERS

KW - SOLID-PHASE SYNTHESIS

KW - MOLECULAR RECOGNITION

KW - PHOTOPHYSICAL PROPERTIES

KW - TRYPTOPHAN FLUORESCENCE

KW - SELECTIVE RECOGNITION

KW - BINDING-PROPERTIES

KW - BETA-CYCLODEXTRIN

KW - SELF-ASSOCIATION

U2 - 10.1016/S0040-4020(03)00468-X

DO - 10.1016/S0040-4020(03)00468-X

M3 - Article

SN - 0040-4020

VL - 59

SP - 3999

EP - 4009

JO - Tetrahedron

JF - Tetrahedron

IS - 22

ER -