SELECTIVE CLATHRATION IN A CAGE-TYPE HOST LATTICE OF CYCLOPHOSPHAZENE

Tris(naphthalene-2,3-dioxy)cyclotriphosphazene (TNDOCTP) forms a chann el-type clathrate with benzene and also a cage-type one with p-xylene. X-Ray analysis of the p-xylene clathrate showed that the cavity size and form were adequate to accommodate para-disubstituted benzenes into the cage lattice. The extracts obtained from the clathrates which cry stallized from a mixture of disubstituted benzenes were analysed by ga s chromatography in order to examine the selectivity toward guests by the clathration. TNDOCTP selects most preferentially the para-disubsti tuted benzenes so that it can isolate para isomers from ortho, meta an d para mixtures. The guests that can be included in the cage-type cavi ty are limited to those having a size and shape similar to that of p-x ylene. Among para-substituted toluenes, the host does not recognise th e difference among methyl, chloro and bromo groups because of their si milarities in size and shape. The crystal grown from an equimolar mixt ure of p-xylene and benzene is a cage-type p-xylene clathrate and incl udes only p-xylene, which indicates that the cage-type crystal of TNDO CTP is chosen in preference to the channel-type one. The lattice stabi lity of the former might be preferable to the latter.