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

基本信息

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

项目摘要

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，我们首先试图提高时间分辨红外系统的灵敏度，然后我们测量了以下所述的分子的瞬态红外光谱，并讨论了激发物种的分子和电子结构。作为具有对称结构的烃分子，我们已经在极性和非极性溶剂中研究了反苯甲酸和二苯基乙炔。作为用电子捐赠（例如氨基或吡咯基）的“推扣”分子，并接受（例如，氰基）组，由偶联的Pi-Electron Systems（苯环）链接在一起，我们已经在（Dimethylamino）苯甲酸（DMABN），Cyanobenobenbenzquincinucine（cbyanlipiney（Cyprrorey）（Cypyrrore）（cyprrorey（celanybabn）和cB）上（cenanylamino）（dimethylamino）（cenanylamino）（cyp）。在这种类型的分子上，已经讨论了在极性环境中电荷转移（CT）激发态的特征结构，氨基或吡咯群垂直于苯环平面扭曲。但是，该结构的实验证据很少，这个问题仍然是研究人员之间引起争议的问题。在本研究中，我们已经测量了DMABN和同位素取代物种的CT和局部激发（LE）的皮秒红外光谱，并根据可靠的振动分配进行了对CT分子结构的讨论，以及与与CBQ和CPP作为与相关结构的分子相比的CT分子结构。我们成功地建立了DMABN CT状态的红外带的振动分配，并揭示了CT状态的电子结构既包含二氨基含量和苯甲酸的贡献。但是，在当前阶段，不幸的是，我们没有关于分子结构的最终结论（平面或扭曲）。