Engineering topics
Ye, Songtao
Publications and source records attributed to Ye, Songtao.
Distinctive Trend of Metal Binding Affinity via Hydration Shell Breakage in Nanoconfined Cavity
Here, we report a distinctive trend in the binding affinity of metal cations when they interact with lacunary Keggin-type polyoxometalate K 7 [α-PW 11 O 39 ] clusters in aqueous media. The binding affinity of metal cations follows the special trends of Li + > Na + > K + for monovalent cations and Mg 2+ > Ca 2+ > Sr 2+ > Ba 2+ for divalent cations, completely reversed from the common trends of Li + < Na + < K + and Mg 2+ < Ca 2+ < Sr 2+ < Ba 2+ for macroion–counterion ion-pair formation in dilution solution. Isothermal titration calorimetry and NMR measurements confirm that the hydration shells of metal cations are significantly broken during the interaction in the nanoscale cavity, making the binding affinity stronger for the cations with smaller ionic sizes instead of hydrated sizes. Furthermore, the same phenomenon is observed for the lacunary Dawson-type clusters, which contain well-defined cavity in their structures as well, demonstrating the universality of this reverse trend and its connection to nanoconfinement effect in small submolecular cavities.
Effect of Cation–π Interaction on Macroionic Self‐Assembly
Abstract A series of rod‐shaped polyoxometalates (POMs) [Bu 4 N] 7 [Mo 6 O 18 NC(CH 2 O) 3 MnMo 6 O 18 (OCH 2 ) 3 CNMo 6 O 18 ] and [Bu 4 N] 7 [ArNMo 6 O 17 NC(CH 2 O) 3 MnMo 6 O 18 (OCH 2 ) 3 CNMo 6 O 17 NAr] (Ar=2,6‐dimethylphenyl, naphthyl and 1‐methylnaphthyl) were chosen to study the effects of cation–π interaction on macroionic self‐assembly. Diffusion ordered spectroscopy (DOSY) and isothermal titration calorimetry (ITC) techniques show that the binding affinity between the POMs and Zn 2+ ions is enhanced significantly after grafting aromatic groups onto the clusters, leading to the effective replacement of tetrabutylammonium counterions (TBAs) upon the addition of ZnCl 2 . The incorporation of aromatic groups results in the significant contribution of cation–π interaction to the self‐assembly, as confirmed by the opposite trend of assembly size vs. ionic strength when compared with those without aromatic groups. The small difference between two aromatic groups toward the Zn 2+ ions is amplified after combining with the clusters, which consequently triggers the self‐recognition behavior between two highly similar macroanions.
Effect of Cation-π Interaction on Macroionic Self-Assembly
Here, a series of rod–shaped polyoxometalates (POMs) [Bu 4 N] 7 [Mo 6 O 18 NC(CH 2 O) 3 MnMo 6 O 18 (OCH 2 ) 3 CNMo 6 O 18 ] and [Bu 4 N] 7 [ArNMo 6 O 17 NC(CH 2 O) 3 MnMo 6 O 18 (OCH 2 ) 3 CNMo 6 O 17 NAr] (Ar=2,6–dimethylphenyl, naphthyl and 1–methylnaphthyl) were chosen to study the effects of cation–π interaction on macroionic self–assembly. Diffusion ordered spectroscopy (DOSY) and isothermal titration calorimetry (ITC) techniques show that the binding affinity between the POMs and Zn 2+ ions is enhanced significantly after grafting aromatic groups onto the clusters, leading to the effective replacement of tetrabutylammonium counterions (TBAs) upon the addition of ZnCl 2 . The incorporation of aromatic groups results in the significant contribution of cation–π interaction to the self–assembly, as confirmed by the opposite trend of assembly size vs. ionic strength when compared with those without aromatic groups. The small difference between two aromatic groups toward the Zn 2+ ions is amplified after combining with the clusters, which consequently triggers the self–recognition behavior between two highly similar macroanions.