A large ionic water cluster H(H(2)O)(28)(+), consisting of a water shell (H(2)O)(26) and an encaged species H(H(2)O)(2)(+) as a center core, was trapped in the well-modulated cavity of a porous metal-organic framework (MOF) {[Co(4)(dpdo)(12)(PMo(12)O(40))(3)](-)}(infinity) and structurally characterized. Degeneration of the protonated water cluster H(H(2)O)(28)(+) into a smaller cluster H(H(2)O)(21)(+) and recovery of H(H(2)O)(28)(+) from the resulting H(H(2)O)(21)(+) cluster in a reversible way demonstrated the unusual stability of the protonated water clusters H(H(2)O)(28)(+) and H(H(2)O)(21)(+) in the robust crystal host. Proton transport and proton/potassium ion exchange through the channels of the crystal host have been investigated by a well-established fluorometry method. X-ray fluorescence experiments and X-ray structural analyses of the exchanged crystals confirmed the occurrence of the proton/potassium ion-exchange reaction and the transformation of the protonated water cluster H(H(2)O)(28)(+) to an ionic cluster K(H(2)O)(27)(+). Comparison of the H(+)/K(+) exchange of H(H(2)O)(28)(+) with that of its neighboring protonated water cluster H(H(2)O)(27)(+) suggested that the abundance of hydrogen bonds associated with the hydronium/water cluster in the H(H(2)O)(28)(+) cluster was essential for proton transport through the Grotthuss mechanism. On the basis of the results, our porous network could be described as a synthetic non-peptide ion channel, in terms of not only structural features but also the functions addressed. Direct observation of the structures of various large ionic water clusters trapped by porous MOFs, coupled with the proton/ion-exchange processes and the reversible dehydration/rehydration, provided valuable insights into the aqueous proton transfer and its mobility pertaining to the large protonated water clusters in the condensed phase.

A large protonated water cluster, H+(H2O)27, has been trapped and stabilized within the well-modulated cavity of a 3D metal-organic framework formed by cobalt(II) and 4,4'-bipyridine-N,N'-dioxide with a globular Keggin structure [PW12O4]3- anion as template. The structurally characterized protonated water cluster might comprise a (H2O)26 shell with Oh symmetry and a monowater core within the center which is suggested to be a hydronium ion with the Eigen model.

Magnetic switchable maleonitriledithiolate (mnt) complexes were studied by density functional theory. The calculations were performed for anion dimers of [RBzPyR'][Ni(mnt)(2)] (RBzPyR' = derivatives of benzylpyridinium) to elucidate magnetostructural correlations and the nature of the weak intermolecular chemical bonding. The calculated results showed that the spin delocalization, favored by the eclipsed stacking and the shorter interlayer distance, was responsible for the diamagnetic character of [1-benzyl-4-aminopyridinium][Ni(mnt)(2)] at low temperature. The weak antiferromagnetic and ferromagnetic interactions were also reproduced for [1-benzyl-4-aminopyridinium][Ni(mnt)(2)] and [1-(4'-fluorobenzyl)pyridinium][Ni(mnt)(2)] at high temperature, respectively. The natural bond orbital analysis suggested that the cooperative effect of the weak intermolecular bondings may be the intrinsic driving force resulting in the switchable property, which is essentially similar to those in organic radicals exhibiting magnetic bistability. Further investigations with varying interlayer distance d, the extent of slippage (slipping distance r and deviation angle alpha), and rotational angle theta suggested that the extent of slippage played an important role in magnetic interactions. Therefore, the abrupt modulation of the extent of slippage in the [Ni(mnt)(2)](-) complexes by external perturbations provided new possibilities for the design of molecular magnetic switching devices.