Enhanced two-photon absorption of hypersensitive transitions induced by coordination field in europium(III) complex

The photoluminescence properties of novel europium(III) complex of the form [Eu(L1)(Antipy)3(ClO4)3] are presented in this manuscript. Under the coordination field of C3 symmetry in Eu(L1)(Antipy)3(ClO4)3, the oscillator strength of 7F0→5D2 and 7F1→5D1 hypersensitive transitions enhances two orders of magnitude compared with pseudo-Oh symmetry in Eu(L2)2(ClO4)3. The red fluorescence emission of Eu(L1)(Antipy)3(ClO4)3 can be efficiently induced by the one- and two-photon absorption of 7F0→5D2 and 7F1→5D1. Furthermore, the two-photon excitation band at 929 nm corresponding to TPA of 7F0→5D2 is 8 nm, which makes it sensitive to excitation wavelength and distinguished from other excitation sources.