X-ray diffraction study on the aggregate structure of 5,10,15,20-tetra(4-sulfophenyl)porphinatopalladium(II)(4-) in aqueous solution
Abstract
The aggregate structure of 5,10,15,20-tetra(4-sulfophenyl)porphinatopalladium(II) ion (PdTPPS4–) in aqueous solution has been investigated in terms of the distance between the porphyrin monomers, by use of absorption spectroscopy, paramagnetic relaxation of NMR signals, and an isomorphic substitution method for X-ray diffraction of the solution. From absorption spectroscopy results it was concluded that the aggregate was regarded as a dimer arising from hydrophobic attraction between the porphyrin rings. Paramagnetic effects on the longitudinal relaxation time (T1) for 13C NMR of PdTPPS4– by the addition of 5,10,15,20-tetra(4-sulfophenyl)porphinatocopper(II)(CuTPPS4–) suggested that the paramagnetic centre was located along a C4-axis of PdTPPS4– in a PdTPPS4––CuTPPS4– dimer. The dimer of PdTPPS4– was determined to have a twisted face-to-face stacked structure (D4d) at a distance of 4.1 Å by the isomorphic substituted X-ray diffraction study on PdTPPS4– and CuTPPS4– solutions.