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 (H(2)pipz)(3)[Mo8O27] 1, (H(2)pipz)[Mo3O10]center dot H2O2, and (H(2)pipz)[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. (C) 2008 Elsevier Inc. All rights reserved.