Rybczyński Patryk, Bousquet Manon H E, Kaczmarek-Kędziera Anna, Jędrzejewska Beata, Jacquemin Denis, Ośmiałowski Borys
Faculty of Chemistry, Nicolaus Copernicus University in Toruń Gagarina Street 7 87-100 Toruń Poland
Nantes Université, CNRS, CEISAM UMR 6230 F-44000 Nantes France
Chem Sci. 2022 Oct 24;13(45):13347-13360. doi: 10.1039/d2sc05044g. eCollection 2022 Nov 23.
Precise tuning of the fluorescence quantum yield, vital for countless applications of fluorophores, remains exceptionally challenging due to numerous factors affecting energy dissipation phenomena often leading to its counterintuitive behavior. In contrast to the absorption and emission wavelength which can be precisely shifted to the desired range by simple structural changes, no general strategy exists for controllable modification of the fluorescence quantum yield. The rigidification of the molecular skeleton is known to usually enhance the emission and can be practically realized the limiting molecular vibrations by aggregation. However, the subtle balance between the abundant possible radiative and non-radiative decay pathways makes the final picture exceptionally sophisticated. In the present study, a series of nine fluorophores obtained by peripheral substitution with two relatively mild electron donating and electron withdrawing groups are reported. The obtained fluorescence quantum yields range from dark to ultra-bright and the extreme values are obtained for the isomeric molecules. These severe changes in emission efficiency have been shown to arise from the complex relationship between the Franck-Condon excited state and conical intersection position. The experimental findings are rationalized by the advanced quantum chemical calculations delivering good correlation between the measured emission parameters and theoretical radiative and internal conversion rate constants. Therefore, the described substituent exchange provides a method to rigorously adjust the properties of molecular probes structurally similar to thioflavin T.
精确调节荧光量子产率对荧光团的无数应用至关重要，但由于影响能量耗散现象的众多因素常常导致其出现反直觉行为，因此仍然极具挑战性。与可通过简单结构变化精确地将吸收和发射波长转移到所需范围不同，目前不存在可控修改荧光量子产率的通用策略。已知分子骨架的刚性化通常会增强发射，并且可以通过聚集来实际限制分子振动。然而，大量可能的辐射和非辐射衰变途径之间的微妙平衡使得最终情况异常复杂。在本研究中，报道了通过用两个相对温和的供电子和吸电子基团进行外围取代而获得的一系列九个荧光团。所获得的荧光量子产率范围从暗到超亮，并且异构体分子获得了极值。发射效率的这些剧烈变化已被证明源于弗兰克 - 康登激发态与锥形交叉点位置之间的复杂关系。通过先进的量子化学计算使实验结果合理化，这些计算在测量的发射参数与理论辐射和内转换速率常数之间提供了良好的相关性。因此，所描述的取代基交换提供了一种严格调节与硫黄素T结构相似的分子探针性质的方法。
