Ab initio investigation on the structures and spectra of the firefly luciferin |
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Authors: | Liu YaJun and Fang WeiHai |
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Affiliation: | (1) College of Chemistry, Beijing Normal University, Beijing, 100875, China |
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Abstract: | The ground state (S0) geometry of the firefly luciferin (LH2) was optimized by both DFT B3LYP and CASSCF methods. The vertical excitation energies (T v) of three low-lying states (S1, S2, and S3) were calculated by TD-DFT B3LYP//CASSCF method. The S1 geometry was optimized by CASSCF method. Its T v and the transition energy (T e) were calculated by MS-CASPT2//CASSCF method. Both the TD-DFT and MS-CASPT2 calculated S1 state T v values agree with the experimental one. The IPEA shift greatly affects the MS-CASPT2 calculated T v values. Some important excited states of LH2 and oxyluciferin (oxyLH2) are charge-transfer states and have more than one dominant configuration, so for deeply researching the firefly bioluminescence, the multireference calculations are desired. Supported by the National Natural Science Foundation of China (Grant No. 20673012) and the Major State Basic Research Development Programs (Grant No. 2004CB719903) |
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Keywords: | firefly luciferin TD-DFT CASSCF CASPT2 |
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