The chemical composition of claim 1, wherein Z is one bridge such that the chemical compound has a general structure (IVa): wherein at least one R3 is a methyl group, wherein at least one R3 is a C5-C7 alkyl group or a C5-C7 substituted alkyl group; wherein at least one R4 is an aryl group or a substituted aryl group; and wherein M comprises one or more guest molecules associated with one or more