Neutral receptor molecules

In the case of cationic host molecules, the binding of a target anion usually must occur in the presence of other counterions and hence association constants often represent more a measure of the effectiveness with which the target anion is bound relative to the others in the system. Neutral receptor molecules do not suffer from this drawback and also have the potential for greater anion selectivity since they do not rely upon nondirectional electrostatic forces to achieve anion coordination. ... 

The unique combination of binding sites for both cations and anions in a neutral receptor molecule leads to hosts with multifunctional complexation properties, eg. for the complexation of both constituents of a salts. 

Effective charge and transition-state structure in solution, 27, 1 Effective molarities of intramolecular reactions, 17,183 Electrical conduction in organic solids, 16,159 Electrochemical methods, study of reactive intermediates by, 19, 131 Electrochemical recognition of charged and neutral guest species by redox-active receptor molecules, 31, 1... 

Receptor molecules, redox-active, electrochemical recognition of charged and neutral guest species... 

Towards electrochemical recognition of neutral guest species by redox-active receptor molecules... 

Receptor chemistry, the chemistry of artificial receptor molecules, represents a generalized coordination chemistry, not limited to transition-metal ions but extending to all types of substrates cationic, anionic, or neutral species of organic, inorganic, or biological nature [1.13]. 

The complexation of various molecular anions by other types of macrocyclic ligands has been reported [3.1-3.4] in particular with cyclophane-type compounds. Two such receptors are represented by the protonated forms of the macropolycycles 40 [3.29] and 41 [3.30]. Quaternary polybipyridinium compounds also bind anionic substrates [3.31]. Progress is also being made towards the developments of neutral anion receptor molecules [3.32]. The thermodynamic and kinetic data for anion complexation by macrocyclic receptors have been reviewed [2.18c]. 

The spherically shaped cryptophanes are of much interest in particular for their ability to bind derivatives of methane, achieving for instance chiral discrimination of CHFClBr they allow the study of recognition between neutral receptors and substrates, namely the effect of molecular shape and volume complementarity on selectivity [4.39]. The efficient protection of included molecules by the carcerands [4.40] makes possible the generation of highly reactive species such as cyclobutadiene [4.41a] or orthoquinones [4.41b] inside the cavity. Numerous container molecules [A.38] capable of including a variety of guests have been described. A few representative examples of these various types of compounds are shown in structures 59 (cyclophane) 60 (cubic azacyclophane [4.34]), 61a, 61b ([4]- and [6]-calixa-renes), 62 (cavitand), 63 (cryptophane), 64 (carcerand). 

Electrochemical Recognition of Charged and Neutral Guest Species by Redox-active Receptor Molecules... 

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