Crystallographic Study of Macrocyclic Cyclophane Inclusion Compounds

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X-Ray crystal analysis of macrocyclic heterocyclophane(N,N^1,N^<11>,N^<111> -tetramethyl-2,11,20,29-tetraaza-[3.3.3.3]paracyclophane[1]) inclusion compounds with benzene, pyridine, CHCl_3, CH_3CN, CO_2, CH_2Cl_2 and CH_2BrCl was undertaken. The crystals of these inclusion compounds show guest dependent polymorphism and are classified as follows: l:benzene(P2_l,Z=4),l:pyridine (Pl,Z=l), l:CHCl_3 (C2, Z=2), l:CH_3CN and l:CO_2 (C2/c, Z=4), and l:CH_2Cl_2 and l:CH_2BrCl (C2/c, Z=8). In these crystalline inclusion compounds,l exists as 'R'-conformer of 'S'-conformer since the macrocyclic conformation of l is frozen in solid state. l is ftacked along the b-axis to form the molecular column which accomodate guest molecules l:l ratio. One molecular column is chiral because the column consistes of all'R'-or all 'S'-conformers of l. The chiral crystals consist of all 'R'-or all 'S'-column, while racemic crystals consist of both 'R'- and 'S'-column. The five different crystal structures can be interpreted from the viewpoint of the packing mode of the columns. The column arrangement is greatly related to the tilt angle of benzene ring in l. This angle depends on the size and shape of the guest molecule. The macrocyclic conformation(C_<2v>) of the uncomplexed l is different from that (C_4 of the complexed l. The conformational analysis of l by nolecular mechanics calculation shows that l has six stable conformation including enantiomer(the difference between maximum and minimum steric energy is 2.3 kcal/mol), suggesting the free interconversion of l among these six conformers in solution. The guest exchange accompanying phase transition was observed when these inclusion compounds were exposed to other gaseous guest molecules. The first step of this process is slow guest exchange until 40-50% exchange is reached and the second step is phase transition with steep gas exchange(90%).