Cavities packing coefficients

Definition of packing coefficients of host cavities (PCcavity)... 

However, packing coefficients of up to 0.70 can be accommodated if the resulting complex is stabilised by strong intermolecular forces such as hydrogen bonds. Interestingly, the above rule also applies when more than one guest molecule is encapsulated in the receptor s cavity. 

Nakano, K., Sada, K., Kurozumi, Y. and Miyata, M. (2001) Importance of packing coefficients of host cavities in the isomerization of open host frameworks guest-size-dependent isomerization in cholic acid inclusion crystals with monosubstituted benzenes. 

PCcavity is the packing coefficient of the guest components in the host cavity PCcavity = (molecular volume of guest molecule) X 2/Vcavity x 100. 

Considering all the isonitriles tested, the catalytic activity of the supramo-lecular capsule was highly dependent on the size, shape, and electronic properties of the substrates, once again underlining the importance of proper packing coefficient of the coencapsulated species in the cavity. The catalytic activity of the capsule was due both to its mild acidity [22] that favors the protonation of the C atom of the isonitrile unit, and the stabilizing effects of the electron-rich cavity through cation-n interactions, which facilitated the hydration reaction. 

After construction of the amorphous cell using the method of Theodorou-Suter ° and geometric free volume analysis of the cell several (four to six) penetrant molecules to improve sampling are inserted at the free volume positions. The cell is further relaxed by 100 ps of a NPT-MD (constant particle number, temperature and pressure) simulation at 1 bar and room temperature before starting a longer (nanoseconds) NVT dynamics. The recorded trajectories of each penetrant gas molecule are analyzed and the diffusion coefficient is determined by means of relation (eqn (1.5)). In Figures 1.2 and 1.3 the packed cell model of polydimethylsiloxane (PDMS) and the trajectory of N2 molecules in the PDMS matrix are reported. The MD simulations show two types of motions of the N2 molecules jumps between cavities and local motion inside cavities. 

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