Conformational preferences and isomerization upon excitation/ionization of 2-methoxypyridine and 2-N-methylaminopyridine

doi:10.1039/c7cp07854d

CORC > 化学研究所 > 中国科学院化学研究所

	Conformational preferences and isomerization upon excitation/ionization of 2-methoxypyridine and 2-N-methylaminopyridine
	Dai, Wenshuai 1,2; Liu, Sheng 1,2; Zhang, Zhe 1,2; Chi, Xiaoping 1,2; Cheng, Min 1; Du, Yikui 1; Zhu, Qihe 1
刊名	PHYSICAL CHEMISTRY CHEMICAL PHYSICS
	2018-03-07
卷号	20 期号:9 页码:6211-6226
ISSN号	1463-9076
DOI	10.1039/c7cp07854d
英文摘要	Conformers from the rotations of the methyl group and the methoxy or methylamino group, namely staggered (s)/eclipsed (e)-cis/trans 2-methoxypyridine (2MOP) and 2-N-methylaminopyridine (2NMP), are studied using theoretical calculations in combination with one-color resonance-enhanced two-photon ionization (1C-R2PI) and mass-analyzed threshold ionization (MATI) spectroscopies. The calculations predict that, for cis 2MOP, trans 2MOP and trans 2NMP, only the s conformers are stable in the S-0, S-1 and D-0 states. However, for cis 2NMP, the stable conformer is staggered in the S-0 state but eclipsed in the S-1 and D-0 states, indicating an isomerization upon the excitation or ionization from the S-0 state. This is experimentally supported by the 1C-R2PI and MATI spectra of 2NMP. Due to the relative instability, the number density of trans 2MOP is too low in the sample to be detected. All the bands in the 1C-R2PI and MATI spectra of 2MOP are assigned to s-cis 2MOP. The energy differences between cis and trans conformers are derived from excitation and ionization energies, indicating another conformational isomerization: stable trans 2NMP in the S-0 and S-1 states but stable cis 2NMP in the D-0 state. For 2MOP, the so-called syn preference previously found for the S-0 state is also observed in the S-1 and D-0 states. The conformational preference and isomerization are discussed with natural bond orbital calculations and reduced density gradient analysis. For 2MOP, the syn preferences are mainly caused by the exchange repulsion among several s-orbitals of the OCH3 group and the pyridine ring. While the relative stabilities of the s and e conformers of cis 2MOP and cis 2NMP are simultaneously influenced by steric repulsion and orbital interactions.
语种	英语
出版者	ROYAL SOC CHEMISTRY
WOS记录号	WOS:000429280100022
内容类型	期刊论文
源URL	[http://ir.iccas.ac.cn/handle/121111/46191]
专题	中国科学院化学研究所
通讯作者	Du, Yikui
作者单位	1.Chinese Acad Sci, Inst Chem, State Key Lab Mol React Dynam, Beijing Natl Lab Mol Sci, Beijing 100190, Peoples R China 2.Univ Chinese Acad Sci, Beijing 100049, Peoples R China
推荐引用方式 GB/T 7714	Dai, Wenshuai,Liu, Sheng,Zhang, Zhe,et al. Conformational preferences and isomerization upon excitation/ionization of 2-methoxypyridine and 2-N-methylaminopyridine[J]. PHYSICAL CHEMISTRY CHEMICAL PHYSICS,2018,20(9):6211-6226.
APA	Dai, Wenshuai.,Liu, Sheng.,Zhang, Zhe.,Chi, Xiaoping.,Cheng, Min.,...&Zhu, Qihe.(2018).Conformational preferences and isomerization upon excitation/ionization of 2-methoxypyridine and 2-N-methylaminopyridine.PHYSICAL CHEMISTRY CHEMICAL PHYSICS,20(9),6211-6226.
MLA	Dai, Wenshuai,et al."Conformational preferences and isomerization upon excitation/ionization of 2-methoxypyridine and 2-N-methylaminopyridine".PHYSICAL CHEMISTRY CHEMICAL PHYSICS 20.9(2018):6211-6226.