Guests anionic

In the present study low temperature (373 K) hydrothermal technique has been employed for the synthesis of Na8[GaSi04]6(C104)2, containing perchlorate as a guest anion. The product obtained was characterized by x-ray powder diffraction, IR and Raman spectroscopy. The product crystallizes with the cubic sodalite in the space... 

As a result of the relatively rigid layers, strong forces are exterted on the interlayer guests in LDHs. From the magnitude of the red shift in the photoluminescence observed on intercalation of [SmWio036] in LDHs, it has been estimated that the layers exert a uniaxial stress of about 14 GPa on the guest anion [96,97]. 

The alignment of 4 -chloro-4-stilbenecarboxylic acid (CSC) intercalated in Mg/Al LDHs has been investigated [197] by electric linear dichroism, which indicated that the guest anions were intercalated as a double layer, with the tilt of the molecular plane being 40°. 

The X-ray crystal structures of the F", Cl , and Br" cryptates of 19-6H demonstrate the inclusion of one of the halide anions in an unsymmetrical fashion. In the case of the small fluoride ion complex a tetrahedral coordination environment is observed for the guest anion with a mean N(H) - P hydrogen-bonding distance of 2.72(8) A. The CP and Br" cryptates exhibit octahedrally coordinated halide ions situated more centrally within the host framework with N(H) - X" distances in the ranges 3.19-3.39 A (X = CP) and 3.33-3.47 A (X = Br ). It is noteworthy that the hydrogen-bonded distances for the anion within the cryptand host are longer by up to ca 0.15 A than those for the other anions in the lattice, suggesting a particularly... 

Earlier discussion [12] of the structures of protonated cryptand/oxoanion assemblies was based on consideration of H-bonds between the encapsulated anion and the NH+ donors of the ciyptand. These interactions are assumed to be responsible for retention of the guest anion in the host ciyptand cavity, both in the sohd state and in solution. We have shown that, in all cases, anion cryptates exhibit at least three, and often more, direct H-bond NH+-Oanion contacts tethering the included oxoanion within the crypt. 

Based on the fundamental charge-dipole interaction, hydrogen bonding need not necessarily mandate the presence of lone electron pairs in the guest anion. If present, this electronic feature dominates the supramolecular behaviour of anions. As a corollary, it is the most prominent aspect to be removed in the construction of so-called non-coordinative anions (BPhj, BHj, closo-CBnHf2 etc.) that are required in the isolation and study of reactive cationic... 

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