Structural dynamics upon photoinduced charge transfer in N,N,N',N'-tetramethylmethylenediamine

Fengzi Ling; Yanmei Wang; Ling Cao; Jie Wei; Dejun Liu; Zhigao Luo; Jinyou Long; Pengfei Wang; Xinli Song; Song Zhang

doi:10.1016/j.saa.2023.122524

Structural dynamics upon photoinduced charge transfer in N,N,N',N'-tetramethylmethylenediamine

Spectrochim Acta A Mol Biomol Spectrosc. 2023 May 15:293:122524. doi: 10.1016/j.saa.2023.122524. Epub 2023 Feb 18.

Authors

Fengzi Ling¹, Yanmei Wang², Ling Cao², Jie Wei², Dejun Liu³, Zhigao Luo⁴, Jinyou Long², Pengfei Wang⁵, Xinli Song⁶, Song Zhang⁷

Affiliations

¹ School of Science, Shenzhen Campus of Sun Yat-sen University, Shenzhen 518107, China; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
² State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
³ Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
⁴ School of Science, Shenzhen Campus of Sun Yat-sen University, Shenzhen 518107, China.
⁵ Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China; Key Laboratory of In-Fiber Integrated Optics, Ministry Education of China, Harbin Engineering University, Harbin 150001, China. Electronic address: pengfei.wang@tudublin.ie.
⁶ State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China. Electronic address: xinli.song@wipm.ac.cn.
⁷ State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China. Electronic address: zhangsong@wipm.ac.cn.

PMID: 36821936
DOI: 10.1016/j.saa.2023.122524

Abstract

The ultrafast structural motion linked to the charge transfer process in Rydberg excited N,N,N',N'-tetramethylmethylenediamine (TMMDA) has been monitored in real time using femtosecond time-resolved photoelectron imaging coupled with quantum chemical calculations. Optical excitation to the 3 s Rydberg state initially populates the charge on one of the two amine groups, resulting in a charge-localized structure in the Franck-Condon (FC) region. As the wavepacket evolves on the 3 s potential surface, the molecular geometry changes with time, leading to the corresponding variation in the charge distribution. The ensuing structural evolution yields two distinct conformers GG⁺ and TT⁺ (see text for nomenclature), both with the charge delocalized between the two nitrogen atoms. By virtue of the sensitivity of the Rydberg electron binding energy (BE) on the nuclear geometry, the time-dependent BE spectrum offers an intuitive mapping of the charge transfer reaction that leads from the initially prepared charge-localized GG-FC structure to the fully charge-delocalized GG⁺ and TT⁺ structures. Complementary computations provide evidence that through-space interaction is responsible for the charge delocalization in the GG⁺ and TT⁺ structures.

Keywords: Charge delocalization; Rydberg state dynamics; Structural dynamics; Time-resolved photoelectron imaging.