(M3L4 + M2L4): a unique example of a co-crystal containing M3L4 and M2L4 metallocages

Structural characterization of a Pd-3(bitmb)(4)Cl-6 center dot Pd-2(bitmb)(4)Cl-4 center dot 18H(2)O center dot 2CH(3)OH(1) (bitmb = 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene) complex shows that it is a unique example of a co-crystal that includes both a M3L4 metallocage, Pd-3(bitmb)(4)Cl-6, and a M2L4 metallocage, Pd-2(bitmb)(4)Cl-4, in a 1 : 1 ratio. Single crystal analysis indicates that the structures of M3L4 and M2L4 in co-crystal 1 are almost identical to those of the free metallocages. However, both the M3L4 and M2L4 metallocages are flexible and their sizes and shapes can be mediated in co-crystal 1 by strong pi center dot center dot center dot pi interactions between the M3L4 and M2L4 metallocages, CH center dot center dot center dot Cl H-bonds between the M3L4 metallocages and so on. Such a packing mode may govern the formation of the M2L4 and M3L4 co-crystal complex in a 1 : 1 ratio. Furthermore, the combined reaction procedures allow the formation of 1 + 1 M2L4 and M3L4 co-crystal complex 1 in the solid state.