Crystal structure and photophysical properties of a novel polyoxomolybdate porphyrin

A novel polyoxomolybdate with a diprotonated porphyrin as counter-cation, namely, 5,10,15,20-tetrakis(4-carboxyphenyl)-21H,22H,23H,24H-porphine(2+) hexamolybdate(VI) pentahydrate, (C48H32N4O8)[Mo6O19]·5H2O or (H2TCPP)[Mo6O19]·5H2O, I, was prepared via the hydrothermal reaction of MoCl5, 5,10,15,20-tetrakis(4-carboxyphenyl)-21H,23H-porphine (TCPP) and distilled water. The crystal structure of hydrated polyoxometalate (POM) salt I was characterized by single-crystal X-ray diffraction. The compound is characterized by an isolated (zero-dimensional, 0D) structure, because it cannot extend via covalent bonds. The structure contains one [Mo6O19]2− anion, one (H2TCPP)2+ cation and five lattice water molecules. Each of the Mo6+ ions is six-coordinated and displays a distorted octahedral motif. The (H2TCPP)2+ cation displays a distorted saddle motif. A three-dimensional (3D) supramolecular framework is formed via hydrogen-bonding interactions. The compound shows a red photoluminescence emission.