Hydrothermal synthesis and characterization of molybdenum — porphyrin hybrid materials

Abstract

This project aims to fabricate porphyrin-intercalated transition metal oxides layered hybrid materials possessing unique structures and properties. The inorganic-organic hybrid materials are designed to exhibit controllable electronic and magnetic properties. The porphyrin molecules are anticipated to mediate the electronic interactions to promote correlated states between transition metal oxideslayers, because of their high polarizability. With the addition of functional groups at the periphery and coordination of a metal centre in the core, they could serve as both active electronic components and structural pillars covalently bonded to the metal oxides layers. Molybdenum oxides were investigated as inorganic host framework to make the intercalated hybrid materials. The porphyrins used were carboxyphenyl and pyridyl porphyrins (including H2(trans-DPyP), H2(p-TCPP), H2(m-TDCPP) and H2(o-TCPP)). The target of this project was to study the synthesis of porphyrin-metal oxides hybrid layered materials by hydrothermal reactions. Hydrothermal/solvothermal synthesis in Pyrex type borosilicate tubes were used to make hybrid materials. Bulk experiments at different pH and temperature conditions were done. Terephthalic acid and tetra(4-carboxyphenyl)porphyrin were widely used as testing samples to investigate coordination between molybdenum framework and carboxylate groups. However, no porphyrin intercalated layered structure materials were synthesized. Instead, a Keggin based porphyrin hybrid material (MoV(=O)(H2O)p-TCPP)2+{[MoV(=O)(H2O)p-TCPP]2[SiMoVI12O40]}2-was coincidently synthesized from tetra(4-carboxyphenyl)porphyrin and MoO3at pH=3.5, which contained one Keggin polyoxoanion coordinated with two bent MoV(=O)tetra(4-carboxyphenyl)porphyrin and two unlinked MoV(=O)(H2O)tetra(4-carboxyphenyl)porphyrin as counter ion. And, this compound was structurally characterized with single crystal X-ray diffraction. For the rest of porphyrins, there was no material synthesized in single crystal form, so the structure of them could not be confirmed. IR spectroscopy and powder X-ray diffraction were done for these products.