Intercalation of a free-base porphyrin into layered tetratitanic acid

An intercalation compound of layered H₂Ti₄O₉ with 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin (H₂tmpyp⁴⁺) was synthesised by a guest-exchange method using the NPrH₃⁺-H_xTi₄O₉ intercalation compound as intermediate. The porphyrin is present as the free base without protonation. Its molecules are arranged with their planes inclined to the [Ti₄O₉]^2- layers because of the high charge density of the host layers. Whereas the fluorescence spectrum of the intercalated H₂tmpyp⁴⁺ indicated that the porphyrin is present as a monomer without stacked aggregation, the fluorescence decayed as rapidly as that of solid powders of H₂tmpyp⁴⁺ 4I^-, suggesting the porphyrin molecules interact with one another in the interlayer space.