Ultrafast Time-Resolved Fluorescence Studies of Intermolecular Charge Transfer Dynamics in Olefin-Tetracyanoethylene Complexes

• Main Authors: Cheng, Ting-Pu, 鄭亭菩
• Other Authors: Cheng, Po-Yuan
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/48juvh

碩士 === 國立清華大學 === 化學系所 === 106 === We studied the charge-transfer (CT) state relaxation dynamics of a series of electron donor-acceptor (EDA) complexes with broadband ultrafast time-resolved fluorescence spectroscopy implemented by optical Kerr gating and transient absorption spectroscopy. The EDA complexes studied here are those containing various olefins (1-hexene, 2-hexene, 1-methylcyclohexene, 2,3-dimethyl-2-butene) as the donor and tetracyanoethylene (TCNE) as the acceptor. In our experiments, the CT state of the EDA complexes are directly reached by femtosecond laser excitation in either CH2Cl2 or CCl4 solutions, and the subsequent temporal evolution of the fluorescence spectra were measured to explore the charge recombination (CR) dynamics. EDA complexes with various arenes, including methyl substituted and non-methyl substituted benzenes, as the donor have been studied previously in our laboratory. We used the total fluorescence intensity function P(t) to analyze CT state relaxation and CR dynamics of EDA complexes. We found two different decay behaviors in these olefin-TCNE complexes. The faster component (<1 ps) was assigned to vibrational relaxation and solvation , the slower component was attributed to CR. We concluded that the most important difference between the olefin-TCNE and arene-TCNE complexes was the electronic coupling strength. The greater electronic coupling strength in the olefin-TCNE complexes extremely accelerates CR reactions and result in a weak dependence of ET rate on the driving-force.