Anions coordinating anions: analysis of the interaction between anionic Keplerate nanocapsules and their anionic ligands

Abstract

Keplerates are a family of anionic metal oxide spherical capsules containing up to 132 metal atoms and some hundreds of oxygens. These capsules holding a high negative charge of -12 coordinate both mono-anionic and di-anionic ligands thus raising its charge till -42 even till -72, which is compensated by the corresponding counter-cations in X-Ray structures. We present an analysis of the relative importance of several energy terms of the coordinate bond between the capsule and ligands like carbonate, sulphate, sulphite, phosphinate, selenate, and a variety of carboxylates, of which the overriding component is the contribution due to solvation/de-solvation effects.

The precise modification of a nanoscaled Keplerate-type polyoxometalate with NH2-groups: reactive sites, mechanisms and dye conjugation

“…Unlike simple POMs, the coordination chemistry of giant POMs has been under-studied, with works focused on nitrogen oxides, 7 carbon dioxide, 28 bidentate acid residues and methoxy groups. 16,29,30…”

“…Unlike simple POMs, the coordination chemistry of giant POMs has been under-studied, with works focused on nitrogen oxides, 7 carbon dioxide, 28 bidentate acid residues and methoxy groups. 16,29,30 The current study is the first in a series on the production of smart systems with potential photocatalytic applications based on the giant POMs {Mo 132 } = (NH 4 ) 42 [Mo VI 72 Mo V 60 O 372 (CH 3 COO) 30 (H 2 O) 72 ]•(∼300H 2 O)•(∼10CH 3 COONH 4 ), organic dyes and supramolecular scaffolds directing the stereo aspect of reactions. Due to both the limited solubility of giant POMs in the majority of organic solvents and their well-known catalytic activities, 31,32 they can be easily separated from the reaction mixture to obtain the desired product.…”

Trapping of Gd(III) Ions by Keplerate Polyanionic Nanocapsules in Water: A 1H Fast Field Cycling NMR Relaxometry Study

“…Kps are hydrophilic and fully soluble in polar solvents. In water, Kps behave as strong electrolytes and dissociate into macroanions and small countercations. , Anionic ligands can exchange with each other, either between internal sites or between an internal site and the solution, depending on the ligand-bonding strength. ,− The number of bound ligands and, consequently, the net charge of the nanocapsule and the protonation state of the inner ligands depend on the Kp concentration and on the nature of the counterions . Kps interact with cations present in solution in different ways and equilibria between cations inside the cavity, trapped in the pores, on the capsule surface, and free in solution are established, which depend on Kp and cation relative concentrations, Kp charge, and cation charge and dimension. ,, The interactions with cations significantly alter the properties and behavior of the capsule, such as charge, acidity, mobility, and solubility .…”