Mesoporous Materials Incorporating a Zinc(II) Complex: Synthesis and Direct Luminescence Quantum Yield Determination

New luminescent inorganic-organic hybrid materials incorporating the luminescent zinc(II) complex ZnL(2) lambda(em) = 457nm and (Phi(em) = 4.4% reference values for ZnL(2); HL = chelating ligand resulting from the reaction between salicylaldehyde and 3-aminopropyltriethoxysilane), covalently bonded to different types of mesoporous silica hosts (namely MCM-41, MCM-48 and SBA-15), were prepared via both the methods of grafting post-synthesis (GPS) and one-pot synthesis (OPS). The products obtained, which form the GPS [(GPS)(Zn/MCM-41), (GPS)(Zn/MCM-48), (GPS)(Zn/SBA-15)] and the OPS [(OPS)(Zn/MCM-41), (OPS)(Zn/MCM-48), (OPS)(Zn/SBA-15)] series, contain the ZnL(2) guest covalently bonded to the silica framework through silicon-oxygen bonds formed when the silane group is placed at the periphery of the Zn(II) coordination sphere. CPS and OPS materials were characterized by powder X-ray diffraction. N(2) adsorption/desorption, thermogravimetric analysis (TGA) and UV/vis spectroscopy. For the new mesoporous materials the emission quantum yield (EQY) was measured by means of an integrating sphere combined with a spectrofluorimeter. The ZnL(2) loading (measured by the ZnL(2)/SiO(2) ratio calculated from TGA data) for MCM-41 appears to be independent of the synthesis procedure, whereas, for both MCM-48 and SBA-15, the ZnL(2)/SiO(2) ratio of the materials obtained via OPS is about four times higher than prodcuts obtained from CPS. The ZnL(2) loaded CPS and OPS series show lambda(em) maxima at about 485 and 455 nm. respectively. Moreover, with reference to EQY (GPS)(Zn/SBA-15) and (OPS)(Zn/SBA-15), although featuring ZnL(2)/SiO(2) ratios of 0.13 and 0.45, respectively, they showed similar EQY values: 2% and 5%. On the contrary, (GPS)(Zn/MCM-41) and (OPS)(Zn/MCM-41) which give similar ZnL(2)/SiO(2) ratios (0.09 and 0.14) exhibit very different EQY, i.e. 2% and 22%, respectively.