Three guest-including coordination solids from a single crystallization: a discrete cage and open-channel networks...

A study of the coordination assemblies that result from the complexation of 1,3,5-tri(4-sulfophenyl)benzene, L3-, with copper(II) in the presence of pyridine is presented. The present results offer some insights into the subtleties of designing coordination polymers and open-channel solids. From an initial crystallization, three different single crystalline solids, 1-3, are obtained. Compounds 1 and 2 are Cu pyridyl complexes of the trianionic form of the ligand whereas compound 3 is a Cu pyridyl complex of the monoprotonated form, HL2-. Compound 1 is a discrete cage complex. Compound 2 is a 1-D ladder structure that has open channels, and compound 3 is a 1-D ribbon structure that assembles into open channels. All three complexes form from the same crystallization in a ratio of 90:9:1, and all three have the same Cu coordination sphere. The exact ratio of products can be altered by varying the Cu counterion or by the addition of methanol. Addition of hexamethylenetetramine results in the exclusive formation of a different network, 4, which is structurally almost identical to the minor product 3. Single-crystal structures of all four solids are presented along with thermal analysis and IR data for the major products. A number of insights into formation of coordination assemblies are obtained. Compound 3 is discussed as an intermediate to 2, and compounds 3 and 4 offer a design paradigm for the formation of open-channel solids from 1-D building blocks.