Second-Sphere Coordination Revisited

Liu, Zhichang; Schneebeli, Severin T.; Stoddart, J. Fraser

doi:10.2533/chimia.2014.315

Cited by 45 publications

(22 citation statements)

References 19 publications

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“…In the resulting coordination complexes, the ligands linked directly to the metal center are referred to (Figure 1b) as the first sphere of coordination for the metal. [25][26][27][28] Meanwhile, another set of ligands can bind to the first-sphere ligands of the coordination complex through noncovalent bonding interactions, leading to second-sphere adducts. Thus, second-sphere coordination of metal centers affords adducts that are essentially complexes of complexes.…”

Section: Introductionmentioning

confidence: 99%

Whither Second-Sphere Coordination?

et al. 2022

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The properties of coordination complexes are dictated by both the metals and the ligands. The use of molecular receptors as second-sphere ligands enables significant modulation of the chemical and physical properties of coordination complexes. In this Mini-Review, we highlight recent advances in functional systems based on molecular receptors as second-sphere coordination ligands, as applied in molecular recognition, synthesis of mechanically interlocked molecules, separation of metals, catalysis, and biomolecular chemistry. These functional systems demonstrate that second-sphere coordination is an emerging and very promising strategy for addressing societal challenges in health, energy, and the environment.

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Section: Introductionmentioning

confidence: 99%

Whither Second-Sphere Coordination?

et al. 2022

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“…The 1:1 and 2:1 adducts between α-cyclodextrin and KAu(CN) 2 are sustained 104,105 for (i) the neutral anticancer chemotherapeutic agent, carboplatin, (ii) the cationic [Rh(cod)-NH 3 )] 2+ as its hexafluorophosphate, 106 and (iii) the anionic AuBr 4 − as its potassium salt. 31,32,78,79 Second-sphere coordination adducts involving βand γ-cyclodextrinsas well as their methylated derivativeswith transition metal complexes, such as ferrocene, 107 [Rh(cod)Cl] 2 , [Pt(cod)X 2 ] (X = Cl, Br, and I), 108,109 cobalt clusters, 110 and the neutral phosphane− transition metal complexes, 111 trans-[Pt(PR 3 )Cl 2 (NH 3 )] where R = Me and Et, were reported in the literature in the 1980s. It would appear that the ability of the readily available cyclodextrins and their methylated derivatives to form adducts with neutral and charged transition metal complexes in aqueous solution is wide in its scope.…”

Section: ■ Conclusionmentioning

confidence: 99%

“…Research on cyclodextrins − has been of particular interest to us. − Not so long ago, we demonstrated , that α-cyclodextrin (α-CD) can encapsulate tetrabromoaurate in the presence of potassium ions, resulting in selective precipitation of a gold adduct, leading to a green gold-recovery technology. It is also well-known − that α-CD can encapsulate selectively substrates with a linear geometry, such as poly(ethylene glycol) and polyiodide complexes. , The linear geometry of Au(CN) 2 – suggests that this substrate could be a good fit inside the cavity of α-CD.…”

Section: Introductionmentioning

confidence: 99%

Supramolecular Gold Stripping from Activated Carbon Using α-Cyclodextrin

Liu

Jones

et al. 2020

J. Am. Chem. Soc.

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We report the molecular recognition of the Au(CN) 2 − anion, a crucial intermediate in today's gold mining industry, by α-cyclodextrin. Three X-ray single-crystal super-structuresKAu(CN) 2 ⊂α-cyclodextrin, KAu(CN) 2 ⊂(α-cyclodextrin) 2 , and KAg(CN) 2 ⊂(α-cyclodextrin) 2 demonstrate that the binding cavity of α-cyclodextrin is a good fit for metal-coordination complexes, such as Au(CN) 2 − and Ag(CN) 2 − with linear geometries, while the K + ions fulfill the role of linking αcyclodextrin tori together as a result of [K + •••O] ion−dipole interactions. A 1:1 binding stoichiometry between Au(CN) 2 − and α-cyclodextrin in aqueous solution, revealed by 1 H NMR titrations, has produced binding constants in the order of 10 4 M −1 . Isothermal calorimetry titrations indicate that this molecular recognition is driven by a favorable enthalpy change overcoming a small entropic penalty. The adduct formation of KAu(CN) 2 ⊂α-cyclodextrin in aqueous solution is sustained by multiple [C−H•••π] and [C−H•••anion] interactions in addition to hydrophobic effects. The molecular recognition has also been investigated by DFT calculations, which suggest that the 2:1 binding stoichiometry between α-cyclodextrin and Au(CN) 2− is favored in the presence of ethanol. We have demonstrated that this molecular recognition process between α-cyclodextrin and KAu(CN) 2 can be applied to the stripping of gold from the surface of activated carbon at room temperature. Moreover, this stripping process is selective for Au(CN) 2 − in the presence of Ag(CN) 2 − , which has a lower binding affinity toward α-cyclodextrin. This molecular recognition process could, in principle, be integrated into commercial gold-mining protocols and lead to significantly reduced costs, energy consumption, and environmental impact.

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“…A variety of transition metal complexes interact with solvents and organic substrates in their second coordination-spheres through non-covalent interaction [1][2][3][4][5][6][7][8][9][10][11]. Such second-sphere coordination, especially hydrogen bonding, brings about a perturbation of the electronic state of the complex and modifies its properties.…”

Section: Introductionmentioning

confidence: 99%