Porphyrin sieves. Designing open networks of tetra(carboxyphenyl)porphyrins by extended coordination through sodium ion auxiliaries

The structural features of two- and three-dimensional multiporphyrin coordi nation polymers in which the free base and zinc-metallated tetra(4-carboxyp henyl)porphyrin (TCPP and ZnTCPP, respectively) building blocks are tessell ated by sodium ion auxiliaries have been evaluated. These network arrays ar e stabilized primarily by ion-pairing forces, exhibiting diverse sodium-pol y(carboxylic/carboxylate) interaction synthons. The observed structures rev eal a common basic motif of a layered organization of the porphyrin species with void spaces between them. In order to optimize multiple coordination of the carboxyphenylporphyrins to the sodium ions these layers stack one on top of the other in a parallel fashion, with the ions located between them . The resulting lattices thus resemble molecular sieve materials, as they a ll contain spacious channels (their van der Waals cross-section varying fro m 3 to 6 Angstrom) which propagate through the stacked layers and entrap ot her molecules. Structures involving the non-metallated TCPP building blocks contain additional channel cavities that extend between the porphyrin laye rs. The channel voids of both types account for 28-40% of the crystal volum e (the upper range referring to the TCPP-based materials), depending on the structural and compositional modifications incorporated into the component species and reaction mixtures. The results provide new insights into the d esigned formulation of structurally rigid multiporphyrin arrays.