Luminescent homo- and hetero-metallic hybrid molecular materials constructed by covalent grafting

In this paper, 3-(triethoxysilyl)-propyl isocyanate (abbreviated as TESPIC) was modified by ethylparaben (EPB) to produce corresponding organic-inorganic monomers (EPB-TESPIC) with two components equipped with covalent bonds, which not only can coordinate to RE ions (Tb3+ and Eu3+) but also act as a sol-gel precursor. Luminescent hybrid materials consisting of terbium-europium complex, covalently bonded to silica-based network, have been obtained in situ via a sol-gel approach. Proton nuclear magnetic resonance spectroscopy (1HNMR) and Fourier transform infrared spectroscopy (FT-IR) were applied to characterize the structure of EPB-TESPIC. UV-visible, phosphorescence, and luminescence spectra were obtained to characterize the photophysical properties of the obtained hybrid material. Through co-hydrolysis and polycondensation, Tb3+ and Eu3+ can be introduced into the same organic-inorganic hybrid monomer, forming Si-O backbones. The experimental results show that the strong luminescence of rare-earth ions substantiates the optimum energy match and effective intramolecular energy transfer between the triplet state energy of coordination complex and the emissive energy level of the rare-earth ions. The hybrid material systems are expected to have potential applications in photophysical sensors.