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Angew Chem Int Ed Engl. 2018 Apr 3;57(15):4067-4072. doi: 10.1002/anie.201800409. Epub 2018 Mar 5.

Effect of Cation-π Interaction on Macroionic Self-Assembly.

Author information

1
Department of Polymer Science, University of Akron, Akron, OH, 44325, USA.
2
Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China.
3
X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
4
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL, 60115, USA.
5
Material Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA.
6
Department of Chemistry, University of Akron, Akron, OH, 44325, USA.

Abstract

A series of rod-shaped polyoxometalates (POMs) [Bu4 N]7 [Mo6 O18 NC(CH2 O)3 MnMo6 O18 (OCH2 )3 CNMo6 O18 ] and [Bu4 N]7 [ArNMo6 O17 NC(CH2 O)3 MnMo6 O18 (OCH2 )3 CNMo6 O17 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 Zn2+ ions is enhanced significantly after grafting aromatic groups onto the clusters, leading to the effective replacement of tetrabutylammonium counterions (TBAs) upon the addition of ZnCl2 . 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 Zn2+ ions is amplified after combining with the clusters, which consequently triggers the self-recognition behavior between two highly similar macroanions.

KEYWORDS:

binding affinity; cation-π interaction; macroionic self-assembly; polyoxometalates; self-recognition

PMID:
29441703
DOI:
10.1002/anie.201800409

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