Protonated Hexaazamacrocycles as Selective K⁺ Receptors

Contact Ion Pairs on a Protonated Azamacrocycle: the Role of the Anion Basicity

“…In a recent study [38], protonated M, formed in a mass spectrometer by ESI, was found to be capable of selectively trapping ppb amounts of the K + ions ubiquitously present in (Table 1) [38]. This conclusion is further corroborated by the fact that a similar behavior was observed when replacing the carboxylic acid with the same concentration of its sodium or ammonium salt (see, for instance, Figures S4 and S5 of the SM section).…”

Imine- and Amine-Type Macrocycles Derived from Chiral Diamines and Aromatic Dialdehydes

“…The determination of the enantiomeric excess of different carboxylic acids has been achieved on the basis of good splitting of the NMR signals for the enantiomers of the bound guest molecules [50][51][52][53]. Interestingly, in the gas phase, amine 15 is able to bind potassium cations, anions, such as carboxylates, but also to function as an acceptor of contact K + /anion pairs [54,55]. Lead(II) complexes of macrocycles 9, 10, 12, and 13 can be reduced and demetallated to give the corresponding free macrocyclic amines 15-18 (Figure 8).…”

“…The determination of the enantiomeric excess of different carboxylic acids has been achieved on the basis of good splitting of the NMR signals for the enantiomers of the bound guest molecules [50][51][52][53]. Interestingly, in the gas phase, amine 15 is able to bind potassium cations, anions, such as carboxylates, but also to function as an acceptor of contact K + /anion pairs [54,55]. The formation of [2 + 2] imines is preferred when enantiopure DACH is condensed with dialdehydes based on two benzaldehyde fragments that are connected by a link X (Figure 9) which enforces the bent conformation of the dialdehyde.…”

Inhibitory Effect of Azamacrocyclic Ligands on Polyphenol Oxidase in Model and Food Systems

“…The host molecules, in general, are large molecules capable of enclosing smaller molecules, and they can be natural, semisynthetic, or completely synthetic molecules. On the other hand, the smaller guest molecules can be cationic, anionic, or neutral like amino acids, organic anions, and some metals …”