Thermodynamics of binding of carboxylates to amphiphilic Eu3+/Cu2+ metallacrown

Abstract

The binding constants of acetate and benzoate to a Pheha-based 15-metallacrown-5 have been determined by a fluorimetric indicator displacement assay demonstrating on a thermodynamic basis the stabilization effect arising from complexation of the less polar carboxylate into the hydrophobic pocket of the metallacrown scaffold.

Facile One‐Pot Route toward Water‐Soluble Lanthanide–Copper–Glycinehydrox­imate 15‐Metallacrown‐5 Complexes

“…[3] A large amount of systematic structural studies of Ln[15MC CuRha -5] complexes derived from α-aminohydroxamic acids with various organic anions have been performed, [4][5][6][7][8][9][10][11][12][13][14] and the affinity of the Ln III ion Scheme 1. It has been demonstrated that the anion affinity for the metallacrown is dependent on the R-substituted hydroximate ligands (Rha).…”

The peculiar behavior of Picha in the formation of metallacrown complexes with Cu(ii), Ni(ii) and Zn(ii) in aqueous solution

“…These metals often possess a series of axial coordi-nation sites available for interactions with solvent molecules or co-ligands. [10][11][12] For these reasons MCs have been studied as recognition agents for anions and cations, [13][14][15][16][17][18][19][20] as single molecule magnets, [21][22][23] as building blocks for mesoporous solids, 24 and as luminescent materials for the purpose of in vivo imaging. 25,26 Despite a number of structural and functional studies, numerous aspects which regulate the stability of MCs in solution and the correlation between the species isolated in the solid state and those present in the solution phase are far from being fully elucidated.…”

Stoichiometric diversity of Ni(ii) metallacrowns with β-alaninehydroxamic acid in aqueous solution

“…MCs are employed for the preparation of molecular magnets (including SMMs), [13][14][15][16][17] of (meso)-porous solids, [18][19][20] of luminescent near-infrared emitting supramolecules, 21 and of supramolecular hosts for anions. [22][23][24][25] Moreover, their stability and the presence of negative-charged oxygen atoms in their cavity make metallacrowns very interesting candidates for obtaining a new generation of hosts for cations. 4,26,27 In the field of functional MC-based supramolecules, a key aspect is the control of the geometry of the scaffold through a proper choice of the metals involved.…”

“…21,28,29 For instance, while both copper 12-MC-4 and 15-MC-5 complexes are characterized by high stabilities, they suffer from the limitation that vacant (unoccupied cavity) metallacrowns have never been isolated or detected in solution irrespective of the geometry of the aminohydroxamate used. 3 To date, copper 15-MC-5 have always been isolated with their cavities occupied by Y 3+ , [30][31][32] Na + , 31 Ag + , 31 Pb 2+ , 31 Hg 2+ , 31 Ca 2+ , 4,27 Ln 3+ , 1,23,26,[32][33][34] or UO 2 2+ 35 as core metals essential for the assembly of the metallamacrocycles, which revealed to be particularly stable. Actually, vacant metallacrowns could be very interesting for the preparation of a new generation of receptors for cations.…”