| Popis: |
This study compares thermodynamic stability of clathrate compounds belonging to three isomorphous series: (MPy4(NCO)2) ∗ 2Py (M = M(II) = Mn, Fe, Co, Ni), (MPy4(NO3)2) ∗ 2Py (M = Mn, Co, Ni, Cu, Zn), and (CuPy4(NO3)2) ∗ 2G (G = pyridine, benzene, THF, chloroform). Thermodynamic parameters (�H av, �S 0 av andG 0 ) of the dissociation of the clathrates were determined from the dependences of the guest equilibrium pressure over the clathrates versus temperature (tensimetric method). Clathrate phases, when different only in the host formula, demonstrated the same order of thermody- namic stability as one expected for the host complexes in solution: Mn Zn for M and NCO > NO3 for X. The influence of the host complex formulation was comparable to the effect of guest template, the effect observed in the third series with the variation of the guest component. This study illustrates a dramatic impact of the stability of the host molecule on the overall stability of the clathrate phases, the impact being comparable to a contribution arising from the host-guest complementarity. |
