Anion Recognition in Water, Including Sulfate, by a Bicyclam Bimetallic Receptor: A Process Governed by the Enthalpy/Entropy Compensatory Relationship

Boiocchi, Massimo; Bonizzoni, Marco; Ciarrocchi, Carlo; Fabbrizzi, Luigi; Invernici, Michele; Licchelli, Maurizio

doi:10.1002/chem.201800067

Cited by 13 publications

(17 citation statements)

References 48 publications

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“…This indicates that coordination of anionic guest in the space between the two macrocyclic subunits induces a more pronounced anion desolvation with a consequent larger entropy contribution, in agreement with what was previously observed in water. 13…”

Section: Resultsmentioning

confidence: 99%

“…For comparison, the structure of [Cu 2 ( 2 )Br] 3+ is also reported. 13 A plot showing thermal ellipsoids is drawn in Figure S13 (see Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

“…In particular, the examination of enthalpy and entropy terms, which were unbalanced or contrasting, disclosed that the contributions due to hydration/dehydration processes overcame any favorable effect because of the nature of the receptor (e.g., steric complementarity). 13…”

Section: Introductionmentioning

confidence: 99%

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Bimacrocyclic Effect in Anion Recognition by a Copper(II) Bicyclam Complex

et al. 2018

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The dicopper(II) complex of the bimacrocyclic ligand α,α′-bis(5,7-dimethyl-1,4,8,11-tetraazacyclotetradecan-6-yl)- o -xylene, 2 , interacts with selected anions in dimethyl sulfoxide solution according to two different modes: (i) halides (Cl – , Br – , and I – ) and N 3 – coordinate the two metal centers at the same time between the two macrocyclic subunits that face each other and (ii) anionic species that do not fit the bridging coordination mode (e.g., NCO – , SCN – , CH 3 COO – , NO 3 – , and H 2 PO 4 – ) interact with copper(II) ions only at the “external” positions or their interaction is too weak to be detected. Occurrence of the bridging interaction is demonstrated by X-ray crystallographic studies performed on the adduct formed by [Cu 2 ( 2 )] 4+ with azide and by electron paramagnetic resonance investigation, as the anion coordination between the two copper(II) centers induces spin–spin coupling. Isothermal titration calorimetry experiments performed on [Cu 2 ( 2 )] 4+ and, for comparison, on [(5,7-dimethyl-6-benzyl-1,4,8,11-tetraazacyclotetradecane)copper(II)], representing the mononuclear analogue, allowed determination of thermodynamic parameters (log K , Δ H , and T Δ S ) associated with the considered complex/anion equilibria. Thermodynamic data showed that adducts formed by [Cu 2 ( 2 )] 4+ with halides and azide benefit from an extra stability that can be explained on the basis of the anion advantage of simultaneously binding the two metal centers, i.e., in terms of the bimacrocyclic effect.

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Section: Resultsmentioning

confidence: 99%

“…For comparison, the structure of [Cu 2 ( 2 )Br] 3+ is also reported. 13 A plot showing thermal ellipsoids is drawn in Figure S13 (see Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

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Bimacrocyclic Effect in Anion Recognition by a Copper(II) Bicyclam Complex

et al. 2018

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“…Furthermore, the coordination of a double negative anion induces a release of water molecules larger than in the case of a monodentate guest. The resulting increase of the translational entropy contribution could favor the recognition process [31]. Among the investigated dicarboxylate anions, binding constants (determined by UV-Vis titrations) decrease along the series dfc 2− > sdbz 2− > tph 2− .…”

Section: Uv-vis Investigations With Aromatic Dicarboxylates Of Differmentioning

confidence: 96%

Section: Uv-vis Investigations With Aromatic Dicarboxylates Of Differmentioning

confidence: 99%

Towards Building Blocks for Supramolecular Architectures Based on Azacryptates

et al. 2020

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In this work, we report the synthesis of a new bis(tris(2-aminoethyl)amine) azacryptand L with triphenyl spacers. The binding properties of its dicopper complex for aromatic dicarboxylate anions (as TBA salts) were investigated, with the aim to obtain potential building blocks for supramolecular structures like rotaxanes and pseudo-rotaxanes. As expected, UV-Vis and emission studies of [Cu2L]4+ in water/acetonitrile mixture (pH = 7) showed a high affinity for biphenyl-4,4′-dicarboxylate (dfc2−), with a binding constant of 5.46 log units, due to the best match of the anion bite with the Cu(II)-Cu(II) distance in the cage’s cavity. Compared to other similar bistren cages, the difference of the affinity of [Cu2L]4+ for the tested anions was not so pronounced: conformational changes of L seem to promote a good interaction with both long (e.g., dfc2−) and short anions (e.g., terephthalate). The good affinity of [Cu2L]4+ for these dicarboxylates, together with hydrophobic interactions within the cage’s cavity, may promote the self-assembly of a stable 1:1 complex in water mixture. These results represent a good starting point for the application of these molecular systems as building units for the design of new supramolecular architectures based on non-covalent interactions, which could be of interest in all fields related to supramolecular devices.

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