Chameleon water:: assemblies confined in nanocapsules

The structures adopted by nanodroplets of water trapped into {Pentagon(12)Linker(30)} type perforated nanocapsules displaying approximate I-h point-group symmetry is studied both from a metric (O-H center dot center dot center dot O bond lengths and H-O center dot center dot center dot O bond angles) and energetic (hydrogen bond strengths) point of view by one of the authors (M.H.). The sizes of the following water assemblies were found to depend on the kind of linker (L) used between the pentagonal {Mo(Mo-5)} type units (P): amorphous aggregates >{H2O}(59) (L=[(Mo2O4)-O-v(HCOO)]), {H2O}(40+1) (L=[(MoO)-O-v(H2O)]), {H2O}(80) (L=[(Mo2O4)-O-V(H2PO2)]), [(NH4+)(n) subset of {H2O}(81-n)] (L=[Mo(2)(V)O4(SO4)]) and {H2O}(100) (L=[(Mo2O4)-O-v(SO4/H2PO2)]) according to earlier studies in Bielefeld. Two main structure types, i.e., amorphous water systems (AW) with no rings or loops extracted/ modeled from the real/observed peak situation and Platonic and/or Archimedean shapes (PW), were identified. These findings are tentatively/ preliminarily discussed with reference to some X-ray diffraction results and infrared as well as H-1 NMR spectroscopy studies on the liquid state. The type of linker influences not only the size of the capsule and pores but also the internal surface with the possibility to change its functionality. How larger assemblies of water molecules react to physical change (in volume) or chemical perturbations (hydrophobic/ hydrophilic internal surface, inclusion of cations) is currently a subject of remarkable interest. (c) 2004 Elsevier B.V. All rights reserved.