Hybrid Silsesquioxane Films Doped with Rhenium Complexes as Oxygen Sensors

M. L. GOMEZ; R. E. PALACIOS; N. A. PIZARRO URZUA; A. VEGA

Mar del Plata

Simposio; SLAP 2018 ? XVI Simposio latinoamericano de Polímeros ? XIV Congreso Iberoamericano de Polímeros; 2018

INTEMA

INTRODUCTIONSilsesquioxanes are polymeric hybrid organic-inorganic materials of structural formula (RSiO1.5)n, where R groups are organic bridges between Si-O-Si bonds. The inorganic nature of these materials makes them inert, resistant to temperature, chemical agents, etc. Meanwhile organic domains promote dispersion of certain compounds within the organic nanodomains to improve the resulting material's properties.1 In this work, two distinct Rhenium complexes with phenanthroline ligands were dispersed within two different silsesquioxane matrices. The first matrix containing a phenyl group and the second one containing a pendant dodecyl chain. The photo emission of these materials in the presence or absence of molecular oxygen (O2) was characterized and the results show a potential use as ratiometric O2 sensors.EXPERIMENTAL METHODSFilms were obtained from hydrolysis and polycondensation of SSO1 and SSO2 precursors in the presence of two rhenium complexes, ReNN-NH2Br or ReNNBr (Chemical Structures in Scheme 1). The films were characterized by FTIR, photoluminescence spectra, photoluminiscence quantum yields and singlet oxygen emission lifetimes. In addition, the potential use of these materials as O2 sensors was evaluated from emission tests, carried out introducing an optical fiber in contact with the films, in a sealed round flask filled with different mixtures of N2 and O2.RESULTS AND DISCUSSIONRhenium complexes were successfully dispersed in silsesquioxane films obtaining optically homogeneous materials. SSO1 and SSO2 undoped films have high intrinsic emission quantum yields; the emission of rhenium complexes was increased when incorporated within the polymer matrix as compared to pure solid rhenium complexes. It was found that both Re complexes were able to generate singlet oxygen.Finally, an increase in the emission of MLCT band was observed with decreasing O2 concentration, whereas the polymeric matrix emission band was practically independent of the O2 concentration. CONCLUSIONNew inert polymeric materials based on silsesquioxanes were tested for their ability to ratiometrically sense O2. The sensing capability depends on both the structure of the Re complex and the structure of the dispersing matrix.