Lanthanide-Titanium Oxo Clusters as the Luminescence Sensor for Nitrobenzene Detection

Abstract

A luminescent lanthanide-titanium oxo cluster of Eu₂Ti₄(μ₂-O)₂(μ₃-O)₄(phen)₂(tbza)₁₀·4CH₃CN (<b>1</b>, Eu₂Ti₄-phen-tbza, phen = 1,10-phenanthroline, Htbza = 4-<i>tert</i>-butylbenzoic acid) was prepared through the reaction of phen, Htbza, Eu(Ac)₃·<i>x</i>H₂O, and Ti(O^<i>i</i>Pr)₄ in acetonitrile. Its overall absolute quantum yield is 65.4% in solid state and 30.2% in CH₂Cl₂, and the detection limit of <b>1</b> for the nitrobenzene (NB) is 10.5 ppb. When the concentration of NB is 40 ppm, the luminescence quenching of <b>1</b> can be observed with the naked eye. Time-resolved excited-state decay measurements indicate that the static quenching process is dominated across the NB concentration of 0-9 ppm. The distinguishable shifts in ¹H NMR spectra of NB together with <b>1</b> confirm the presence of π···π stacking interactions between the organic ligands in <b>1</b> and the NB, which plays a key contribution for the quenching of luminescence.