Ligand-assisted J-type aggregates of zinc porphyrin: anticooperative molecular organization in self-assembled bolaamphiphile.

Bolaamphiphilic zinc porphyrins bearing a 2-pyridylethynyl or 4-methoxyphenylethynyl group, Zn(PyPor) or Zn(ArPor), respectively, were newly synthesized in order to explore the molecular organizing behaviours within the interior hydrophobic layer of aqueous self-assemblies. Well-ordered J-type aggregates of Zn(PyPor) were formed in aqueous self-assembled bolaamphiphile, whereas J-type aggregates of Zn(ArPor) were disordered. The titration experiments suggest that axial coordination bond improves the structural uniformity of the J-type aggregates of Zn(PyPor). In a homogeneous isotropic media, on the other hand, Zn(PyPor) formed an antiparallel dimer through self-complementary coordination. Unprecedented molecular organization of ligand-assisted J-type aggregates is described in the term of anticooperative effect under the bulk conditions.