Abstract
A series of Ln3+-metal centered complexes, Ln(TTA)3(DPPI) (Ln = La, 1; Ln = Eu, 2; Ln = Tb, 3; or Ln = Gd, 4) [(DPPI = N-(4-(1H-imidazo [4,5-f][1,10]phenanthrolin-2-yl)phenyl)-N-phenylbenzenamine) and (TTA = 2-Thenoyltrifluoroacetone)] have been synthesized and characterized. Among which, the Eu3+-complex shows efficient purity red luminescence in dimethylsulfoxide (DMSO) solution, with a Commission International De L’ Eclairage (CIE) coordinate at x = 0.638, y = 0.323 and ΦEuL = 38.9%. Interestingly, increasing the amounts of triethylamine (TEA) in the solution regulates the energy transfer between the ligand and the Eu3+-metal center, which further leads to the luminescence color changing from red to white, and then bluish-green depending on the different excitation wavelengths. Based on this, we have designed the IMPLICATION logic gate for TEA recognition by applying the amounts of TEA and the excitation wavelengths as the dual input signal, which makes this Eu3+-complex a promising candidate for TEA-sensing optical sensors.
Highlights
Stimulus-response materials, which are new types of intelligent materials, have received widespread attention [1,2,3,4]
Lanthanide-based complexes are of particular interest owing to their specific luminescent properties, which can be applied in various areas, such as pure red organic light-emitting diodes [8], cellular recognition [5], fluorescence sensors [9,10,11], magnetic materials and catalysis [12]
By regulating the energy of the ligand and the outer stimulations, the energy transfer between the ligands and the Ln-metal centers can be controlled, leading the emission to be “Off-On”, or leading to a change in color and intensity [20], which leads to the emission becoming a favorable and promising candidate for visual detection [21,22]
Summary
Stimulus-response materials, which are new types of intelligent materials, have received widespread attention [1,2,3,4]. As shown in the emission spectra of complex 2 at different excitations without TEA (Figure S13), basically only the Eu3+-centered emissions were observed, manifesting that the emission of the DPPI ligand itself in complex 2 was hampered due to the total energy transfer to the metal center. The alternative intensity between the Eu3+-centered and residual fluorescence of the 5DoPfP11I ligand can be tuned by applying different excitation wavelengths in complex 2 after the addition of TEA, accompanying with various color emissions as a whole (Figure 3). TEA provides active hydrogen protons that result in acid-base interactions; on the other hand, it causes the electronic distribution and energy state changes in the ILCT-structured DPPI ligand due to molecular interactions [47], and leads to the color emission variations and the TEA detecting capabilities of the Eu3+complex [48,49]
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