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.