Sildenafil saccharinate (
SS) for
ms solvates with a large nu
mber of solvents, which are included in distorted hexagonalcavities constituted with N
(+)-H···N
(-) and C-H···O interactions. All these solvates, except the
methanolate, are isostructural andcontain various host-guest O-H···O and C-H···O interactions and also an intra
molecular N-H···O hydrogen bond in the sildenafilentity. The C-H···O bonds, in particular, are strong and nu
merous and play an i
mportant role in stabilizing the crystal packing atseveral levels. The solute-solvent ratio varies a
mong the isostructural solvates because of differences in guest size. Solvents withs
maller volu
me occupy the peripheries of the cavity, while larger solvents are located within the cavity. All the solvates are convertedeasily to the apohost upon heating, and this transfor
mation is associated with a rearrange
ment of several C-H···O interactions inthe structure. The apohost could also be prepared by grinding the two co
mponents, and this procedure led to
mixtures of crystallineand a
morphous for
ms. When this ground sa
mple was heated at 120
mages/entities/deg.gif">C, it was converted into the crystalline
SS apohost. In thisfa
mily of host-guest co
mpounds the host fra
mework is largely invariant and robust, and the guest
molecules only play a bystanderrole in the packing. The totally different crystal structure of the
methanol solvate argues in favor of using the ter
m pseudopolymorphto describe
modulations in the structural landscape of a host-guest syste
m.