Three Isomeric Zn(II)-Sn(IV)-Zn(II) Porphyrin-Triad-Based Supramolecular Nanoarchitectures for the Morphology-Dependent Photocatalytic Degradation of Methyl Orange

Abstract

Three isomeric Zn(II)-Sn(IV)-Zn(II) porphyrin-based triads (T2, T3, and T4) were synthesized by the reaction of common Zn( II) porphyrins (ZnL) with different Sn(IV) porphyrins (SnPn). The Sn(IV) porphyrin precursors differ with respect to the position of the pyridyl-N atoms. All compounds were characterized by H-1 NMR, UV-vis, fluorescence spectroscopy, electrospray ionization-mass spectrometry, and field-emission scanning electron microscopy measurements. In these structures, the intramolecular cooperative metal-ligand co-ordination of the 3-pyridyl nitrogen in SnP3 with axial ZnL and the pi-pi interactions between the adjacent porphyrin triad are the determining factors affecting the nanostructures of T3. Owing to the geometrical constraints of the SnP2 center, this type of interaction is not possible for T2. Therefore, only the pi-pi interactions affect the self-assembly process. In the case of SnP4, intermolecular coordinative interactions and then pi-pi interactions are responsible for the nanostructure of T4. The morphology-dependent photocatalytic degradation of methyl orange (MO) dye in aqueous solution under visible light irradiation was observed for these photocatalysts, and the degradation ratio of MO varied from 76 to 94% within 100 min. Nanorod-shaped T3 exhibited higher performance compared to nanosphere T2 and nanoflake T4.