Synthesis and characterization of two new TiO(2)-containing benzothiazole-based imine composites for organic device applications

The effect of the presence of titanium dioxide in two new imines, (E,E)-(butane-1,4-diyl)bis(oxybutane-4,1-diyl) bis(4-{[(benzo[d][1,3]thiazol-2-yl)methylidene]amino}benzoate) (SP1) and (E)-N-[(benzo[d][1,3]thiazol-2-yl)methylidene]-4-dodecylaniline (SP2), on the properties and stability of imine:TiO(2) composites for organic device applications were examined. The investigated titanium dioxide (in anatase form, obtained via the sol–gel method) exhibited a surface area of 59.5 m(2)/g according to Brunauer–Emmett–Teller theory, and its structure is a combination of both meso- and microporous. The average pore diameter calculated by the Barrett–Joyner–Halenda method was 6.2 nm and the cumulative volume of pores was 0.117 m(3)/g. The imine SP1 exhibited columnar organization (Col), while SP2 revealed a hexagonal columnar crystalline phase (Col(hk)). The imine:TiO(2) mixtures in various weight ratio (3:0, 3:1, 3:2, 3:3) showed a lower energy gap and HOMO–LUMO energy levels compared to pure TiO(2). This implies that TiO(2) provides not only a larger surface area for sensitizer adsorption and good electron collection, but also causes a shift of the imine energy levels resulting from intermolecular interaction. Also the temperature of the phase transition was slightly affected with the increase of TiO(2) concentration in imine-based composites. The changes observed in the Fourier transform middle-infrared absorption (FT-MIR) spectra confirmed the significant influence of TiO(2) on structural properties of both investigated imines. Similar interactions of oxygen vacancies existing on the TiO(2) surface with SP1 and SP2 were observed. The imine:TiO(2) mixtures showed good air stability and reusability, which demonstrates its potential for organic device applications.