Axial vs equatorial: Capturing the intramolecular charge transfer state geometry in conformational polymorphic crystals of a donor-bridge-acceptor dyad in nanosecond-time-scale.
Axial vs equatorial: Capturing the intramolecular charge transfer state geometry in conformational polymorphic crystals of a donor-bridge-acceptor dyad in nanosecond-time-scale.
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DOI：
10.1063/5.0134792
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发表时间：
2023-02-07
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研究了供体-桥-受体 (D-B-A) 二元体 p-(CH3)2N-C6H4-(CH2)2-(1-芘基)/PyCHDMA 的两种构象多晶型物，其中电子供体 (D) 部分 p-(CH3)2N-C6H4/DMA 通过桥连基团 (B)、-CH2-CH2- 连接到电子受体 (A)芘部分。尽管像 PyCHDMA 这样的分子二元体有潜力通过光诱导分子内电荷转移 (ICT) 过程将太阳能转化为电流，但主要挑战是晶体中光诱导 ICT 过程的实时研究，这是设计固态光电材料所必需的。单晶的时间相关单光子计数 (TCSPC) 测量表明，热力学形式 PyCHDMA1（芘和 DMA：轴向）的 ICT 态寿命为 ∼3 ns，而对于动力学形式 PyCHDMA20（芘和 DMA：赤道），ICT 态寿命为 ∼7 ns，而用 375 nm 辐射光激发。多晶型晶体被光激发，随后在时间分辨 X 射线衍射 (TRXRD) 测量中用粉红色劳厄 X 射线束进行探测。 TRXRD 结果表明，在 ICT 状态下，由于电子从 DMA 部分中的叔 N 原子转移到桥连基团和芘部分，N 原子上的孤对电子和键对之间的排斥力降低，导致两种多晶型物中 C–N–(CH3)2 部分的平面性。自然键轨道计算和赫什菲尔德分配的部分原子电荷分析也证实了这一点。尽管使用 TDDFT 结果进行的片段间电荷转移 (IFCT) 分析表明，对于两种构象异构体中的电荷转移激发，电子从 DMA 部分转移到大部分芘部分，但桥连基团在其中几乎没有发挥作用。
Two conformational polymorphs of a donor–bridge–acceptor (D-B-A) dyad, p-(CH3)2N-C6H4-(CH2)2-(1-pyrenyl)/PyCHDMA, were studied, where the electron donor (D) moiety p-(CH3)2N-C6H4/DMA is connected through a bridging group (B), –CH2–CH2–, to the electron acceptor (A) moiety pyrene. Though molecular dyads like PyCHDMA have the potential to change solar energy into electrical current through the process of photoinduced intramolecular charge transfer (ICT), the major challenge is the real-time investigation of the photoinduced ICT process in crystals, necessary to design solid-state optoelectronic materials. The time-correlated single photon counting (TCSPC) measurements with the single crystals showed that the ICT state lifetime of the thermodynamic form, PyCHDMA1 (pyrene and DMA: axial), is ∼3 ns, whereas, for the kinetic form, PyCHDMA20 (pyrene and DMA: equatorial), it is ∼7 ns, while photoexcited with 375 nm radiation. The polymorphic crystals were photo-excited and subsequently probed with a pink Laue x-ray beam in time-resolved x-ray diffraction (TRXRD) measurements. The TRXRD results suggest that in the ICT state, due to electron transfer from the tertiary N-atom in DMA moiety to the bridging group and pyrene moiety, a decreased repulsion between the lone-pair and the bond-pair at N-atom induces planarity in the C–N–(CH3)2 moiety, in both polymorphs. The Natural Bond Orbital calculations and partial atomic charge analysis by Hirshfeld partitioning also corroborated the same. Although the interfragment charge transfer (IFCT) analysis using the TDDFT results showed that for the charge transfer excitation in both conformers, the electrons were transferred from the DMA moiety to mostly the pyrene moiety, the bridging group has little role to play in that.
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DOI：
10.1039/a708604k
发表时间：
1998-03-21
期刊：
JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS
影响因子：
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作者：
Coppens, P;Fomitchev, DV;Culp, K
通讯作者：
Culp, K
DOI：
10.1039/jr9640001996
发表时间：
1964-01-01
期刊：
JOURNAL OF THE CHEMICAL SOCIETY
影响因子：
--
作者：
COHEN, MD;SCHMIDT, GMJ
通讯作者：
SCHMIDT, GMJ
DOI：
10.1063/1.4978240
发表时间：
2017-03
期刊：
Structural dynamics (Melville, N.Y.)
影响因子：
--
作者：
Basuroy K;Chen Y;Sarkar S;Benedict J;Coppens P
通讯作者：
Coppens P
影响因子：
4.4
作者：
BECKE, AD
通讯作者：
BECKE, AD
影响因子：
56.9
作者：
Collet, E;Lemée-Cailleau, MH;Techert, S
通讯作者：
Techert, S