Self-assembly of Pd4L2 Supramolecular Cage and Permanganate Anion Adsorption Behavior in Water.

A novel metal–organic cage 1·8PF₆⁻ was precisely self-assembled using polynitrogen pyrazine-triazine ligand as linker L¹ and bpyPd(NO₃)₂ as coordination corner (where 1·8PF₆⁻ = [(bpyPd)₄L¹₂]⁸⁺·8PF₆⁻; L¹ = 4, 6-bis((pyrazin-2-ylmethyl)amino)-1,3,5-triazin-2-ol); bpy = 2,2′-bipyridine) in aqueous solution. The capsule-like coordination cage 1·8PF₆⁻ was fully characterized by single-crystal X-ray diffraction analysis, ¹H and ¹³C-NMR and ESI–MS analysis. In the crystal structure, cage 1 closely stacked into a stable 3D framework structure with a regular channel. By employment of such crystalline adsorbent material, permanganate anion (MnO₄⁻) can be rapidly adsorbed into cationic channel and exchanged with hexafluorophosphate anion from water, in which the crystallinity of cage 1 remained unaffected before and after adsorption. Moreover, the anion adsorption and exchanging behavior was revealed by Fourier transform infrared spectra (FTIR), powder X-ray diffraction analysis (PXRD), scanning electron microscopy (SEM), electron adsorption and fluorescence spectroscopy. [ABSTRACT FROM AUTHOR]