Design strategies for solid-state supramolecular arrays containing both mixed-metalated and freebase porphyrins

The design of predictable multichromophoric supramolecular arrays of freeba se and metallo porphyrins constitutes an essential first step toward the sy nthesis of light-harvesting complexes. We now report crystal engineering st rategies to achieve the synthesis of controllable and predictable porphyrin ic multichromophores in the solid state. The coordination complexes of meta l halides, MX2 (M = Cd, Hg, Pb; X = Br, I), with freebase tetrapyridylporph yrin (TPyP) form either 1D, [(HgX2)(2)TPyP].2TCE, 1, or 2D, [(MX2)TPyP].4TC E, (M = Pb, 2; Cd, 3) polymeric networks. The porphyrin cavities in these c rystalline networks can be selectively populated with various metal cations to generate ordered multiporphyrinic supramolecular arrays without distort ing the coordination networks, either by (a) crystallizing the metal halide s and TPyP in the presence of suitable metal salts or by (b) reacting metal halides with a mixture of freebase and metallo porphyrins in specific stoi chiometric ratios. A design limit has been reached following approach b, sy nthesis of the complexes using 100% metalated TPyP results in a change in s tructure due to intermolecular MTPyP coordination. The UV/vis and fluoresce nce spectra recorded on partially metalated complexes indicate the presence of the expected absorption and emission bands. Additionally, complex 1 rev eals an unusual clathration behavior, wherein the stacking features perpend icular to the porphyrin plane adjust to allow inclusion of variable amounts of identical guest solvent molecules without modification of the layered s tructure.