设计的 TICT 化合物：两种不同长度和基态几何形状的萘酰亚胺-π-二甲基苯胺共轭物的比较,Physical Chemistry Chemical Physics

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设计的 TICT 化合物：两种不同长度和基态几何形状的萘酰亚胺-π-二甲基苯胺共轭物的比较
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2022-12-07 , DOI: 10.1039/d2cp04250a
Justina Jovaišaitė ₁ , Paulius Baronas ₁ , Gediminas Jonusauskas ₂ , Dalius Gudeika ₃ , Alytis Gruodis ₄ , Juozas V Gražulevičius ₃ , Saulius Juršėnas ₁

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两种新的扭曲分子内电荷转移 (TICT) 供体-π-受体化合物是通过两种类型的不同刚性接头将众所周知的电子受体萘酰亚胺单元与经典的电子供体二甲基苯胺组合而成的。与不同极性的掺杂聚合物基质的固态溶剂化实验相比，不同极性溶剂中分子的稳态和时间分辨光谱相结合，可以区分溶剂化和构象确定的过程。光物理测量表明，非极性溶液具有高达 70% 的高荧光量子产率，这是处于激发电荷转移 (CT) 状态的预扭曲/平面分子的特性。^-1伴随着荧光量子产率三个数量级的下降。这是出现的 TICT 状态的结果，因为二甲基苯胺扭曲到与萘酰亚胺核心垂直的位置。分子的 TICT 反应启用了一个额外的非辐射激发衰变通道，如果在刚性聚合物基质中禁止扭曲，则该通道不存在。瞬态吸收光谱用于可视化激发态动力学并获得激发态反应常数，表明 TICT 可能发生在 Franck-Condon 区域和溶剂化预扭曲/平面 CT 状态。两种分子都经历相同的光物理过程，然而，更长的连接子和更高的激发态偶极矩决定了更快的激发态反应。

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TICT compounds by design: comparison of two naphthalimide-π-dimethylaniline conjugates of different lengths and ground state geometries

Two new twisted intramolecular charge transfer (TICT) donor-π-acceptor compounds were designed by combining a well-known electron acceptor naphthalimide unit with a classic electron donor dimethylaniline through two types of different rigid linkers. The combined steady-state and time-resolved spectroscopy of molecules in solvents of different polarities in comparison to solid-state solvation experiments of doped polymer matrixes of different polarities allowed distinguishing between solvation and conformation determined processes. The photophysical measurements revealed that non-polar solutions possess high fluorescence quantum yields of up to 70% which is a property of pre-twisted/planar molecules in the excited charge transfer (CT) states. The increase of polarity allows tuning the Stokes shift through all the visible wavelength range up to 8601 cm⁻¹ which is accompanied by a three orders of magnitude drop of fluorescence quantum yields. This is a result of the emerged TICT states as dimethylaniline twists to a perpendicular position against the naphthalimide core. The TICT reaction of molecules enables an additional non-radiative excitation decay channel, which is not present if the twisting is forbidden in a rigid polymer matrix. Transient absorption spectroscopy was employed to visualize the excited state dynamics and to obtain the excited state reaction constants, revealing that TICT may occur from both the Franck-Condon region and the solvated pre-twisted/planar CT states. Both molecules undergo the same photophysical processes, however, a longer linker and thus a higher excited state dipole moment determines the faster excited state reactions.

更新日期：2022-12-07

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