McLay James R W, Sutton Joshua J, Shillito Georgina E, Larsen Christopher B, Huff Gregory S, Lucas Nigel T, Gordon Keith C
Department of Chemistry, University of Otago, P.O. Box 56, Dunedin 9001, New Zealand.
Inorg Chem. 2021 Jan 4;60(1):130-139. doi: 10.1021/acs.inorgchem.0c02555. Epub 2020 Dec 21.
A series of electron donor-acceptor compounds are reported in which both the donor and acceptor strengths are systematically altered using mono-, bi-, and terthiophene as donors and benzo[][1,2,5]thiadiazole (btd), dipyrido[3,2-:2',3'-]phenazine (dppz), and the corresponding rhenium(I) complex, [ReCl(CO)(dppz)], as acceptors. The electronic properties of the compounds are characterized using electrochemistry, electronic absorbance and emission spectroscopies, and transient absorption spectroscopy. The effect of donor and acceptor strengths on frontier molecular orbital localization and on the charge-transfer (CT) character of optical transitions is modeled using density functional theory (DFT) calculations. The electronic absorption spectra of the compounds investigated are dominated by intraligand charge-transfer (ILCT) transitions, where the CT character is shown to increase across the series from mono- to bi- to terthiophene but not significantly across the acceptor series. Emission is shown to originate from the absorbing state. Long-lived nonemissive states have been observed using transient absorption spectroscopy and assigned using triplet-state DFT calculations, which indicate that the lowest energy excited state has more thiophene-localized π,π* character with an increasing number of appended thiophenes.
报道了一系列电子供体-受体化合物，其中使用单噻吩、双噻吩和三噻吩作为供体，苯并[][1,2,5]噻二唑（btd）、二吡啶并[3,2-:2',3'-]菲咯嗪（dppz）以及相应的铼（I）配合物[ReCl(CO)(dppz)]作为受体，系统地改变了供体和受体强度。使用电化学、电子吸收和发射光谱以及瞬态吸收光谱对这些化合物的电子性质进行了表征。利用密度泛函理论（DFT）计算对供体和受体强度对前沿分子轨道定位以及光跃迁的电荷转移（CT）特性的影响进行了建模。所研究化合物的电子吸收光谱主要由配体内电荷转移（ILCT）跃迁主导，其中CT特性显示从单噻吩到双噻吩再到三噻吩在整个系列中增加，但在受体系列中增加不显著。发射显示源自吸收态。使用瞬态吸收光谱观察到了长寿命的非发射态，并使用三重态DFT计算进行了归属，结果表明随着连接噻吩数量的增加，最低能量激发态具有更多噻吩定位的π,π*特性。
