Reinvestigation of hybrid organic–inorganic materials based on molybdate and piperazininum cations: Influence of the synthesis conditions on the chemical composition and characterizations of the photochromic properties

The reactivity of the [Mo7O24]6− anion towards the structure directing-reagent piperazine (pipz) has been investigated and new synthetic routes to achieve the known (H2pipz)3[Mo8O27] 1, (H2pipz)[Mo3O10]·H2O 2, and (H2pipz)[Mo5O16] 3 molybdenum(VI) containing compounds are proposed. The role of the pH on the stabilization of the different compounds and their interconversion pathways is discussed. Compounds 1 and 2 show photochromic behavior under UV excitation, related to the particular organization of the organic component around the mineral framework. Their optical properties are reported and commented.