Syntheses, structures and properties of two new organic-inorganic hybrid materials based on ε-Zn Keggin units {ε-PMo^V₈Mo^VI₄O_40-x(OH)_xZn₄}

Two novel organic-inorganic hybrids, Na[PMo^V₈Mo^VI₄O₃₈(OH)₂Zn₄][pyim]₂·1.5H₂O [ε(pyim)₂] (pyim = 2-(2-pyridyl)-imidazole) and [PMo^V₈Mo^VI₄O₃₇(OH)₃Zn₄]₂[pyim]₆·4H₂O [ε₂(pyim)₆], based on ε-Zn Keggin units {ε-PMo^V₈Mo^VI₄O_40-x(OH)_xZn₄}, have been successfully synthesized under hydrothermal conditions by controlling the pH values. Structural analysis indicates that the framework of ε(pyim)₂ is a 1D chain constructed by monomeric ε-Zn units modified by pyim ligands, while ε₂(pyim)₆ is an isolated structural compound with dimeric ε-Zn units modified by pyim ligands. This is the first isolated structure of the ε-Keggin POMs system. The luminescent and electrochemical properties of ε(pyim)₂ and ε₂(pyim)₆ were investigated. ε₂(pyim)₆ also shows high catalytic activity for the esterification of phosphoric acid with equimolar lauryl alcohol to monoalkyl phosphate ester (MAP).