Structures and Dynamics of Charge-Separated Excited States Studied by Picosecond Infrared Spectroscopy

皮秒红外光谱研究电荷分离激发态的结构和动力学

• 批准号: 11440171
• 负责人: OKAMOTO Hiromi
• 金额: $ 5.89万
• 依托单位: Okazaki National Research Institutes (2000)The University of Tokyo (1999)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B).
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11440171/
• 关键词: Ultrafast Spectroscopy; Transient Infrared Spectroscopy; Electronically Excited; Charge Transfer; Picosecond; Molecular Structure; (Dimethylamino) benzonitrile

In this project, we have first tried to improve the sensitivity of the time-resolved infrared system, and then we have measured transient infrared spectra of molecules described in the following, and have discussed molecular and electronic structures of the excited species. As hydrocarbon molecules with symmetric structures, we have studied on trans-stilbene and diphenylacetylene in polar and non-polar solvents. As"push-pull"molecules with electron donating (ex. amino or pyrrolyl) and accepting (ex. cyano) groups linked by conjugated pi-electron systems (benzene rings), we have studied on (dimethylamino)benzonitrile (DMABN), cyanobenzquinuclidine (CBQ), and (cyanophenyl)pyrrole (CPP). On molecules of this type, characteristic structures of charge-transfer (CT) excited states in polar environments, with the amino or pyrrolyl groups twisted perpendicularly to the benzene ring plane, have been discussed. However, experimental evidence for the structure is scant and this problem is still a matter of controversy among researchers. In the present study, we have measured picosecond infrared spectra of CT and locally excited (LE) states of DMABN and the isotope-substituted species, and have discussed on the CT molecular structure based on the reliable vibrational assignments, as well as from the comparison with CBQ and CPP as molecules with related structures. We have succeeded in establishing vibrational assignments of infrared bands of the CT state of DMABN, and have revealed that the electronic structure of the CT state contains both quinoidal and benzenoidal contributions. However, in the present stage, we do not have the final conclusion (planar or twisted) about the molecular structure, unfortunately.

在这个项目中，我们首先尝试提高时间分辨红外系统的灵敏度，然后测量了下面描述的分子的瞬态红外光谱，并讨论了激发态物质的分子和电子结构。作为具有对称结构的烃分子，我们研究了极性和非极性溶剂中的反式二苯乙烯和二苯乙炔。作为具有通过共轭π电子系统（苯环）连接的给电子基团（例如氨基或吡咯基）和受电子基团（例如氰基）的“推拉”分子，我们研究了（二甲氨基）苯甲腈（DMABN）、氰基苯奎宁环（CBQ）和（氰基苯基）吡咯（CPP）。对于此类分子，我们讨论了极性环境中氨基或吡咯基垂直于苯环平面扭曲的电荷转移（CT）激发态的特征结构。然而，该结构的实验证据很少，这个问题仍然是研究人员之间存在争议的问题。在本研究中，我们测量了DMABN和同位素取代物质的CT和局部激发（LE）态的皮秒红外光谱，并基于可靠的振动分配讨论了CT分子结构，以及与CBQ和CPP作为具有相关结构的分子的比较。我们成功地建立了 DMABN CT 态红外波段的振动分配，并揭示了 CT 态的电子结构同时包含醌型和苯型贡献。然而，不幸的是，在现阶段，我们还没有关于分子结构（平面或扭曲）的最终结论。

项目成果

Hiromi Okamoto: "Picosecond infrared spectroscopy of electronically excited trans-stilbene in solution in the fingerprint region"Journal of Physical Chemistry A. 103. 5852-5857 (1999)

Hiromi Okamoto：“指纹区域溶液中电子激发反式二苯乙烯的皮秒红外光谱”物理化学杂志 A. 103. 5852-5857 (1999)

H.Okamoto: "Picosecond infrared spectroscopy of electronically excited trans-stilbene in solution in the fingerprint region"J.Phys.Chem.A. 103. 5852-5857 (1999)

H.Okamoto：“指纹区域溶液中电子激发反式二苯乙烯的皮秒红外光谱”J.Phys.Chem.A。

Takaaki Ishibashi: "Picosecond transient infrared spectra and structure of S1 diphenylacetylene in solution"Chemical Physics Letters. 325. 212-218 (2000)

Takaaki Ishibashi：“溶液中S1二苯乙炔的皮秒瞬态红外光谱和结构”化学物理快报。

H.Okamoto: "Picosecond transient infrared spectrum of 4-(dimethylamino) benzonitrile in the fingerprint region."J.Phys.Chem.A. 104. 4182-4187 (2000)

H.Okamoto：“指纹区域中 4-（二甲氨基）苯甲腈的皮秒瞬态红外光谱。”J.Phys.Chem.A.

Hiromi Okamoto: "Infrared and Raman spectra of 4-(dimethylamino) benzonitrile and isotopomers in the ground state and vibrational analysis"Chemical Physics. 260. 193-214 (2000)

Hiromi Okamoto：“4-（二甲氨基）苯甲腈和同位素在基态下的红外和拉曼光谱以及振动分析”化学物理。