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A Europium Complex With Excellent Two‐Photon‐Sensitized Luminescence Properties
Author(s) -
Hao R.,
Li M.,
Wang Y.,
Zhang J.,
Ma Y.,
Fu L.,
Wen X.,
Wu Y.,
Ai X.,
Zhang S.,
Wei Y.
Publication year - 2007
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200700413
Subject(s) - luminescence , excited state , materials science , lone pair , photochemistry , lanthanide , europium , moiety , two photon absorption , triazine , fluorescence , molecule , stereochemistry , chemistry , atomic physics , laser , organic chemistry , optoelectronics , optics , polymer chemistry , ion , physics
We report the synthesis and excellent two‐photon‐sensitized luminescence properties of a new complex [Eu(tta) 3 dmbpt] (tta = henoyltrifluoroacetonate; dmbpt = 2‐( N,N ‐diethyl‐2,6‐dimethylanilin‐4‐yl)‐4,6‐bis(3,5‐dimethylpyrazol‐1‐yl)‐1,3,5‐triazine) that exhibits the highest efficiency of lanthanide luminescence when excited by near‐infrared (NIR) laser pulses (action cross section of two‐photon‐excited fluorescence δ × Φ F : 85 GM at 812 nm and 56 GM at 842 nm; 1 GM = 10 –50 cm 4 s photon –1 molecule –1 ). Compared to a previously reported [Eu(tta) 3 dpbt] complex, (dpbt = 2‐( N,N ‐diethylanilin‐4‐yl)‐4,6‐bis(3,5‐dimethylpyrazol‐1‐yl)‐1,3,5‐triazine), [Eu(tta) 3 dmbpt] has two excess methyl groups at the 2,6‐positions of the phenyl ring. Crystallographic data of dmbpt show that the 2,6‐dimethyl substitutes bring about a significant twist in the conformation of the diethylamino group compared to that in dpbt, which severely influences the conjugation in the ground state between the electron lone pair of N in the –N(CH 2 –) 2 moiety and the aromatic electron system in dmbpt. The large two‐photon absorption (TPA) cross section of dmbpt is mainly derived from its large static dipole moment difference between the S 0 and the S 1 states, which is partly responsible for the high capability of two‐photon‐sensitized luminescence of [Eu(tta) 3 dmbpt]. The broader two‐ and single‐photon excitation windows and the superior two‐photon‐sensitized luminescent properties in the long‐wavelength NIR region of [Eu(tta) 3 dmbpt] compared to [Eu(tta) 3 dpbt] are also explained according to the calculated results and twisted structure.