吾人以時間相關單光子技術系統和密度泛函理論計算研究部分花青素的光物理性質，線性部分花青素L-Mero4之電子施體為吲哚，電子受體為茚滿二酮，施體與受體以一四碳共軛鏈當作橋樑，以S-trans構形較為穩定。苯基取代線性部分花青素P-L-Mero4因為有苯環取代基使得其因立體障礙而改以S-cis構形較為穩定。以515 nm之飛秒雷射當激發光源激發L-Mero4和P-L-Mero4，測得其螢光曲線並以兩個或三個自然指數衰減函數適解。L-Mero4溶於不同溶劑的第一個生命期約為30-150 ps，第二個生命期約為200-720 ps，在非極性溶液第一個生命期振幅百分比約為90 %，在高極性溶液則是第二個生命期振幅百分比約為90 %；P-L-Mero4溶於不同溶劑的第一個生命期約為15-150 ps且振幅百分比約為10 %，第二個生命期約為150-500 ps且振幅百分比約為90 %。理論計算結果發現L-Mero4和P-L-Mero4基態至 ππ^(* )能態為主要吸收，為HOMO → LUMO躍遷，而第二電子躍遷至CT能態之振子強度較小，為HOMO → LUMO +1躍遷。當L-Mero4溶於低極性溶劑和P-L-Mero4溶於各溶劑時，CT能態能量較 ππ^(* )能態低，兩激發態能態次序與吸收不同，光激發至 ππ^(* )能態後能量內部轉移至CT能態，造成量子產率較低；當L-Mero4溶於高極性溶劑時，CT能態能量較 ππ^(* )能態高，兩激發態次序翻轉使得其次序與吸收相同，量子產率較高。兩分子的基態都較激發態極性，造成不正常的Lippert-Mataga圖形，且吸收峰因溶劑極性改變其位移較放光峰明顯。根據所建立的動力學模型進行生命期指認，因能態翻轉導致緩解行為的不同，L-Mero4溶於低極性溶劑和P-L-Mero4溶於各溶劑時，指認第一個生命期為 ππ^(* )能態生命期，主要緩解至CT能態，第二個生命期為CT 能態生命期，主要緩解至基態；L-Mero4溶於高極性溶劑時，指認第一個生命期為CT能態生命期，主要緩解至 ππ^(* )能態，第二個生命期為 ππ^(* )能態生命期，主要緩解至基態。根據生命期與溶劑物理性質的關係，可以解釋兩分子的緩解行為，並與動力學模型之解釋和理論計算相符。

We have studied the photophysical properties of L-Mero4 and P-L-Mero4 using time-correlated single photon counting and density functional theory calculation. The donor of L-Mero4 is indole, indandione is the acceptor, and tetramethinine is the bridge. The most stable configuration of L-Mero4 is S-trans, but P-L-Mero4 is S-cis because of steric hindrance. The 515 nm femtosecond laser served as an excitation light source. The fluorescence curves were fitted with multi-exponential functions. The first lifetimes of L-Mero4 in different solvents are about 30-150 ps, and the second lifetimes are about 200-720 ps. The first lifetime amplitudes in the non-polar solutions are about 90 %, but in the polar solutions are about 90 %; The first lifetimes of P-L-Mero4 in the different solvents are about 15-150 ps, and the second lifetimes are about 150-500 ps. The first lifetime amplitudes in all solutions are about 90 %. According to the theoretical calculations, transition to ππ^(* )state has the most oscillator strength, and is assigned to the HOMO → LUMO conversion. Transition to the CT state is poor, which is the HOMO → LUMO +1 transition. When L-Mero4 is dissolved in a low-polar solvent and P-L-Mero4 is dissolved in each solvent, the energy of CT state is lower than that of ππ^(* )state. The sequence of two excited states is different in the absorption and emission. When the sample is excited to ππ^(* )state, the energy will transfer to the CT energy state, resulting in a low quantum yield. When L-Mero4 is dissolved in a highly polar solvent, the CT energy energy is higher than the ππ^(* )state energy state, and the two excited states are reversed. The sequence of two excited states is the same in the absorption and emission, and the quantum yield is high. The ground states of both molecules are more polar than the excited state, resulting in an abnormal Lippert-Mataga pattern, and the absorption peak shifts due to the change of solvent polarity is more obvious than the emission peak shifts. According to the kinetic model, the lifetimes can be assigned. When L-Mero4 is dissolved in a less polar solvents and P-L-Mero4 is dissolved in each solvent, the first lifetimes are assigned as ππ^(* )state, mainly decay to the CT state. The second lifetimes are assigned as CT state, mainly decay to the ground state; when L-Mero4 is dissolved in the high polar solvent, the first lifetimes are assigned as the CT energy, mainly decay to the ππ^(* )state. The second lifetimes are assigned as ππ^(* )state, mainly decay to the ground state. According to the relationship between the lifetimes and the photophysical properties of the solvent, the excited state relaxation of the two molecules can be explained and consistent with the theoretical calculation and the kinetic model.

1. Mayer, B.; Regler, A.; Sterzl, S.; Stettner, T.; Koblmüller, G.; Kaniber, M.; Lingnau, B.; Lüdge, K.; Finley, J. J., Long-Term Mutual Phase Locking of Picosecond Pulse Pairs Generated by a Semiconductor Nanowire Laser. Nat. Commun. 2017, 8, 15521.
2. Kulinich, A. V.; Ishchenko, A. A., Merocyanine Dyes: Synthesis, Structure, Properties and Applications. Russ. Chem. Rev. 2009, 78, 141.
3. Cai, J.; Li, X.; Yue, X.; Taylor, J. S., Nucleic Acid-Triggered Fluorescent Probe Activation by the Staudinger Reaction. J. Am. Chem. Soc. 2004, 126, 16324-16325.
4. Würthner, F.; Yao, S.; Debaerdemaeker, T.; Wortmann, R., Dimerization of Merocyanine Dyes. Structural and Energetic Characterization of Dipolar Dye Aggregates and Implications for Nonlinear Optical Materials. J. Am. Chem. Soc. 2002, 124, 9431-9447.
5. Zitzler-Kunkel, A.; Lenze, M. R.; Kronenberg, N. M.; Krause, A.-M.; Stolte, M.; Meerholz, K.; Würthner, F., Nir-Absorbing Merocyanine Dyes for Bhj Solar Cells. Chem. Mater. 2014, 26, 4856-4866.
6. Silvi, S.; Arduini, A.; Pochini, A.; Secchi, A.; Tomasulo, M.; Raymo, F. M.; Baroncini, M.; Credi, A., A Simple Molecular Machine Operated by Photoinduced Proton Transfer. J. Am. Chem. Soc. 2007, 129, 13378-13379.
7. Tomasi, J.; Mennucci, B.; Cammi, R., Quantum Mechanical Continuum Solvation Models. Chem. Rev. 2005, 105, 2999-3094.
8. Lakowicz, J. R., Principles of Fluorescence Spectroscopy: Springer, 2006.
9. Condon, E. U., Nuclear Motions Associated with Electron Transitions in Diatomic Molecules. Phys. Rev. 1928, 32, 858-872.
10. Born, M.; Oppenheimer, R., Zur Quantentheorie Der Molekeln. Annalen der physik 1927, 389, 457-484.
11. Pokorna, S.; Olżyńska, A.; Jurkiewicz, P.; Hof, M., Hydration and Mobility in Lipid Bilayers Probed by Time-Dependent Fluorescence Shift. In Fluorescent Methods to Study Biological Membranes, Springer: 2012; pp 141-159.
12. Yeh, S.-C. A.; Patterson, M. S.; Hayward, J. E.; Fang, Q. In Time-Resolved Fluorescence in Photodynamic Therapy, Photonics, Multidisciplinary Digital Publishing Institute: 2014; pp 530-564.
13. Murphy, C. B.; Zhang, Y.; Troxler, T.; Ferry, V.; Martin, J. J.; Jones, W. E., Probing Förster and Dexter Energy-Transfer Mechanisms in Fluorescent Conjugated Polymer Chemosensors. J. Phys. Chem. B 2004, 108, 1537-1543.
14. Weidemaier, K.; Tavernier, H.; Swallen, S.; Fayer, M., Photoinduced Electron Transfer and Geminate Recombination in Liquids. J. Phys. Chem. A 1997, 101, 1887-1902.
15. de Silva, A. P.; de Silva, S. A., Fluorescent Signalling Crown Ethers;‘Switching On’of Fluorescence by Alkali Metal Ion Recognition and Binding in Situ. J. Chem. Soc., Chem. Commun. 1986, 1709-1710.
16. Fabbrizzi, L.; Poggi, A., Sensors and Switches from Supramolecular Chemistry. Chem. Soc. Rev. 1995, 24, 197-202.
17. Klymchenko, A. S., Solvatochromic and Fluorogenic Dyes as Environment-Sensitive Probes: Design and Biological Applications. Acc. Chem. Res. 2017, 50, 366-375.
18. Uchiyama, S.; Takehira, K.; Yoshihara, T.; Tobita, S.; Ohwada, T., Environment-Sensitive Fluorophore Emitting in Protic Environments. Org. Lett. 2006, 8, 5869-5872.
19. Slama-Schwok, A.; Blanchard-Desce, M.; Lehn, J. M., Intramolecular Charge Transfer in Donor-Acceptor Molecules. J. Phys. Chem. 1990, 94, 3894-3902.
20. Petrič, A.; Jacobson, A. F.; Barrio, J. R., Functionalization of a Viscosity-Sensitive Fluorophore for Probing of Biological Systems. Bioorg. Med. Chem. Lett. 1998, 8, 1455-1460.
21. Blatt, E.; Treloar, F. E.; Ghiggino, K. P.; Gilbert, R. G., Viscosity and Temperature Dependence of Fluorescence Lifetimes of Anthracene and 9-Methylanthracene. J. Phys. Chem. 1981, 85, 2810-2816.
22. Sasaki, S.; Drummen, G. P. C.; Konishi, G.-i., Recent Advances in Twisted Intramolecular Charge Transfer (TICT) Fluorescence and Related Phenomena in Materials Chemistry. J. Mater. Chem. C 2016, 4, 2731-2743.
23. Yang, J.-S.; Lin, C.-J., Fate of Photoexcited Trans-Aminostilbenes. J Photochem. Photobiol. A: Chemistry 2015, 312, 107-120.
24. Ito, A.; Ishizaka, S.; Kitamura, N., A Ratiometric TICT-Type Dual Fluorescent Sensor for an Amino Acid. Phys. Chem. Chem. Phys. 2010, 12, 6641-6649.
25. Reddy, T. S.; Reddy, A. R., Synthesis and Fluorescence Study of 6, 7-Diaminocoumarin and Its Imidazolo Derivatives. Dyes Pigments 2013, 96, 525-534.
26. Sıdır, İ.; Sıdır, Y. G., Estimation of Ground and Excited State Dipole Moments of Oil Red O by Solvatochromic Shift Methods. Spectrochim. Acta A 2015, 135, 560-567.
27. Woodward, R. B., Structure and the Absorption Spectra of Α,Β-Unsaturated Ketones. J. Am. Chem. Soc. 1941, 63, 1123-1126.
28. Chen, H.-J., et al., S-Cis Diene Conformation: A New Bathochromic Shift Strategy for near-Infrared Fluorescence Switchable Dye and the Imaging Applications. J. Am. Chem. Soc. 2018, 140, 5224-5234.
29. Van Mourik, T.; Gdanitz, R. J., A Critical Note on Density Functional Theory Studies on Rare-Gas Dimers. J. Chem. Phys. 2002, 116, 9620-9623.
30. Becke, A. D., Density-Functional Exchange-Energy Approximation with Correct Asymptotic Behavior. Phys. Rev. A 1988, 38, 3098.
31. https://sites.google.com/site/miller00828/in/solvent-polarity-table.
32. https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Aldrich/General_Information/labbasics_pg144.pdf.
33. Turro, N. J., Modern Molecular Photochemistry; University Science Books: Sausalito, California, 1991.