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Excitation and deexcitation processes of Eu(III) benzo-15-crown-5 complex studied on comparing with its first coordination sphere |
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| Authors: | Tomoo Yamamura Wataru Sugiyama Hiroyasu Hotokezaka Masayuki Harada Hiroshi Tomiyasu Yoshiyuki Nakamura |
| Institution: | a Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Okayama, Meguro, Tokyo 152-8550, Japan b Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313, Japan c Department of Chemistry and Material Engineering, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan d Chemical Resources Laboratory, Tokyo Institute of Technology, 4259, Nagatsuta, Midori, Yokohama, Kanagawa 226-8503, Japan |
| Abstract: | The coordination sphere and the deexcitation mechanism of the Eu(III) benzo-15-crown-5 complex, Eu(B15C5), were studied with references of the Eu(III) complexes with a similar coordination sphere; the dibenzo-18-crown-6 complex, Eu3(B218C6)2, and the cryptand2.2.1] complex, Eu(2.2.1]). NMR spectroscopy reveals that the Eu(B15C5) complex is quite stable in acetonitrile solution whereas only 40% of the Eu(III) ion forms the complex in the equimolar Eu(NO3)3 and B218C6 acetonitrile solution. The coordination sphere of the Eu(III) complexes in acetonitrile solutions were also discussed by the degenerate 7F0→5D0 transition energy levels. The Eu(B15C5) have a negative shift compared with the europium(III) nitrate in acetonitrile and it is explained by the coordination of both nitrate ions and the crown ether ligand. Energy transfer from the n–π* excited state located in the catechol structure to the central europium ion was first observed as the sensitized luminescence of 5D0→7FJ. The excited state lifetime of the Eu(B15C5) complex was first determined as 201 μs in the present study. |
| Keywords: | Europium(III) benzo-15-crown complexes Excited state lifetime Coordination sphere Deexcitation mechanism |
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