| Project/Area Number |
11440210
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
物質変換
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| Research Institution | Tohoku University |
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Principal Investigator |
TERO Shozo Tohoku University, Institute of Multidisciplinary Research for Advance Materials, Professor, 多元物質科学研究所, 教授 (80111318)
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| Co-Investigator(Kenkyū-buntansha) |
IKOMA Tadaaki Tohoku University, Institute of Multidisciplinary Research for Advance Materials, Associate Research, 多元物質科学研究所, 助手 (10212804)
AKIYAMA Kimio Tohoku University, Institute of Multidisciplinary Research for Advance Materials, Associate Prof., 多元物質科学研究所, 助教授 (10167851)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Triple-bond conjugated molecules / Diphenylpolyynes / Triplet states / Zero-field splitting constants / Spin-orbit interaction |
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| Research Abstract |
The following are the main results obtained in the present study.
(1) Diphenylpolyynes (DPY) have a linear planar structure belonging to the D_<2h> point group in the T_1 states, which were assigned to ^3B_<1u> (π_xπ_x^*) in character.
(2) The T_1 (π_xπ_x^*) states of DPY have unusually large negative D values for the ZFS parameters that increase with increasing the molecular size.
(3) The large negative D value was interpreted in terms of the spin-orbit interaction between the T_1(^3π_xπ_x^*) state and the upper-lying ^3Au (π_xπ_y^*) state.
(4) The energy gap between these two states was determined from the observed D values and the calculation of the spin-orbit matrix, indicating that the value decreases with increasing the number of triple bonds.
(5) The rapid radiationless transition was also found in the decay from the T_1 state to the S_0 state. The k_<nr> value increases with the decrease in the energy separation between the T_1 and S_0 states, indicating the importance of the Franck-Condon factor between them for the nonradiative deactivation.
(6) The appearance of the satellites due to the b_<1g> vibronic bands in the phosphorescence spectra of DPY suggests that the potential surface in the T_1 states would be shallow along the b_<1g> coordinate by the vibronic coupling between the T_1 (π_xπ_x^*) and the ^3π_xπ_y states promoted by the ring twisting motion.
(7) Therefore, it is concluded that the energy proximity between the T_1 (^3B_<1u>:π_xπ_y^*) and Tu(^3Au:π_xπ_y^*) states in DPY not only increases the negative D values of the ZFS parameters by the spin-orbit interaction but also accelerates the nonradiative decay from the T_1 state by the vibronic interaction.
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