Coordination Polymers as Template for Mesoporous Silica Films: A Novel Composite Material Fe(Htrz) 3 @SiO 2 with Remarkable Electrochemical Properties

While attempting to confine Fe(Htrz)3 (Htrz = 1,2,4,-1H-triazole) into a mesoporous silica matrix during its formation by electrochemically assisted self-assembly (EASA), we have discovered that such spin crossover complex is likely to act as the template (in place of the surfactant species) to form in one step a composite mesoporous material (Fe(Htrz)3@SiO2). The EASA method usually leads to the vertical growth of mesoporous silica thin films owing to the electroinduced condensation of silica precursors (i.e., tetraethoxysilane, TEOS) around tubular micelles (i.e., made of cetyltrimethylammonium bromide, CTAB) oriented orthogonally to the underlying support. In the presence of Fe(Htrz)3 in the starting sol (in addition to TEOS and CTAB), two distinct situations can be reached. At low Fe(Htrz)3 concentration (≤3 mM), the vertically aligned mesostructure is formed and Fe(Htrz)3 complexes are incorporated along with the surfactant phase, but most of them are released upon surfactant removal. At high Fe(Htrz...