Twisted Intramolecular Charge Transfer (TICT) Controlled by Dimerization: An Overlooked Piece of the TICT Puzzle.
Twisted Intramolecular Charge Transfer (TICT) Controlled by Dimerization: An Overlooked Piece of the TICT Puzzle.
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由二聚化控制的扭曲分子内电荷转移（TICT）：一个被忽视的TICT难题。
DOI：
10.1021/acs.jpca.1c00629
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发表时间：
2021-04-15
期刊：
影响因子：
--
通讯作者：
Zietz B
中科院分区：
文献类型：
--
作者：
El-Zohry AM;Orabi EA;Karlsson M;Zietz B
有机染料在太阳能电池中表现出了很高的效率，这主要归功于这种染料在连接到半导体表面时存在的推挽策略。我们深入研究了氰基丙烯酸酯类染料，主要是L1染料的基本光物理性质，发现了独特的发射性质，这些性质依赖于许多因素，如溶剂的极性和染料的浓度，可以呈现出这一类染料的完整发射图像。L1染料在低浓度下(约纳摩尔级)表现为分子内电荷转移(ICT)发射态，当浓度增加到微摩尔量级时，在特定溶剂中表现出扭曲的分子内电荷转移(TICT)发射态。此外，L1染料ICT和TICT状态的相关发射寿命取决于溶剂的碱性，突出了氢键形成在控制这些状态方面的作用。密度泛函理论计算深入了解了染料的光物理性质，揭示了在低浓度下，羧基之间的氢键触发了二聚反应。利用飞秒瞬时吸收，我们确定了TICT的形成速率在(160-650fs)−1的范围内，这取决于所研究的氰基丙烯酸染料的大小。因此，除了溶剂极性和受主强度参数之外，我们在这里增加了一个新的维度来控制TICT状态的形成。这些发现并不局限于所研究的染料，我们预计许多有机羧酸染料也显示出类似的特性。
Organic dyes have shown high efficiencies in solar cells, which is mainly attributed to the push–pull strategy present in such dyes upon attaching to the semiconductor surfaces. We deeply studied the fundamental photophysical properties of cyanoacrylic dyes, mostly the L1 dye, and found unique emission properties that depend on many factors such as the solvent polarity and the concentration of the dye and could present a complete emission picture about this family of dyes. The L1 dye shows an intramolecular charge transfer (ICT) emission state at low concentrations (approximately nanomolar scale) and shows a twisted intramolecular charge transfer (TICT) emission state in specific solvents upon increasing the concentration to the micromolar scale. Moreover, the associated emission lifetimes of the ICT and TICT states of the L1 dye depend on solvent basicity, highlighting the role of hydrogen bond formation on controlling such states. Density functional theory calculations are performed to gain insight into the photophysical properties of the dye and revealed that H-bonding between the carboxylic groups triggers the dimerization at low concentrations. Using femtosecond transient absorption, we assigned the rate of TICT formation to be in the range (160–650 fs)−1, depending on the size of the studied cyanoacrylic dye. Therefore, we add herein a new dimension for controlling the formation of the TICT state, in addition to the solvent polarity and acceptor strength parameters. These findings are not limited to the studied dyes, and we expect that numerous organic carboxylic acids dyes show similar properties.
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