Anion recognition by coordinative interactions: metal–amine complexes as receptors

Abstract

Alfred Werner's complexes of formula [M(III)(NH(3))(6-n)X(n)]X(3-n) involved inert metal centres (M = Cr, Co), and anions X(-)'frozen' in the coordination sphere, a circumstance which allowed the isolation of a variety of isomers. Amine complexes of labile transition metal ions, studied later, do not form isomers, yet they allow the investigation of the fast and reversible interaction of the anion X(-) with the metal-amine core. On these bases, anion receptors of varying degrees of sophistication have been synthesised, which consist of coordinatively unsaturated polyamine metal complexes and whose vacant coordination sites can be occupied by anion donor atoms. A thoughtful design of the polyamine framework may introduce geometrical selectivity, resulting from the matching between anion shape and size and the geometrical features of receptor's cavity. Compared to their purely organic counterparts, metal containing receptors display several advantages: (i) metal-anion interactions are strong enough to more than compensate anion dehydration energy, which allows recognition studies to be carried out in water; (ii) transition metal ions of different electronic configurations exhibit different geometrical preferences, which addresses anion binding and introduces a further element of selectivity. Chosen examples of polyamine metal complexes, including macrocycles and cages, displaying selective binding tendencies towards anions will be illustrated in this tutorial review.

A coumarin-derived useful scaffold exhibiting Cu2+ induced fluorescence quenching and fluoride sensing (On–Off–On) via copper displacement approach

“…The dependence arises because the history affects the value of an internal state [28]. Since the experiments were performed with almost equal amount of Cu 2+ and F -ions (5 equiv) it is quite reasonable to understand that copper is not completely displaced from the probe and upon addition of fluoride anion complexation occurred in which F -remained coordinated (6+Cu 2+ ….F -) [29][30] with a complex, 6+Cu 2+ .…”

Characterization of Salophen Co(III) Acetate Ionophore for Nitrite Recognition

“…While a great number of contributions have been made in the past decades, it has so far remained difficult to deviate from the Hofmeister selectivity sequence and to discriminate highly hydrophilic ions from lipophilic ones [1][2][3][4]. The difficulty in obtaining ionophores with similar properties as the ones developed for cations results from their intrinsic nature.…”

[12]aneN3-based BODIPY as a selective and sensitive off–on sensor for the sequential recognition of Cu2+ ions and ADP

“…The chemistry of macrocyclic polyamines has been received much attention due to their widespread applications in coordination chemistry, medicinal chemistry, biochemistry, and material chemistry [1][2][3][4]. Because of their protonation property at physiological conditions, macrocyclic polyamines often act as positive-charged units in constructing DNA condensation agents and non-viral gene vectors [5][6][7][8].…”