Hong Kyeong-Im, Cho Kayoung, Park Hyunjun, Park JaeHong, Jang Woo-Dong
Department of Chemistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea.
Department of Chemistry and Nanoscience, Ewha Womans University, 52, Ewhayeodae-gil, Seodaemun-gu, Seoul 03760, Republic of Korea.
ACS Appl Mater Interfaces. 2024 Aug 28;16(34):45788-45797. doi: 10.1021/acsami.4c13228. Epub 2024 Aug 19.
A fluorescent dye, a dithiophene-conjugated benzothiazole derivative (), was prepared to have high fluorescence emission quantum yields (Φ) across various organic solvents. Its emission color modulation, from bright blue to deep red, was achieved through intramolecular charge transfer (ICT), acid-base equilibrium, and host-guest chemistry. Although it exhibits a weak solvatochromic effect, exhibited a bright fluorescence emission around 480 nm upon excitation at 390 nm in most solvents. In polar solvents, such as MeOH (methanol), EtOH (ethanol), DMF (-dimethylforamide), and DMSO (dimethyl sulfoxide), an additional ICT emission band emerged around 640 nm, notably intense in DMSO, resulting in a bright greenish-white emission (Φ = 0.67). The addition of 1,8-diazabicyclo[5,4.0]undec-7-ene (DBU) altered emission characteristics, reducing emission from the local excited (LE) state and enhancing ICT state emission. The degree of emission spectral change saturation with DBU addition varied with the solvent nature. Polar solvents with high dielectric constants, like DMSO and DMF, saw a complete disappearance of LE state emission with 5 equiv of DBU, resulting in a deep red emission (Φs of 0.53 and 0.48, respectively). Femtosecond transient absorption spectroscopy and time-resolved photoluminescence measurements elucidated the excited-state dynamics, revealing a long-lived excited state (τ = 10.3 ns) at a lower energy emission (640 nm), identified as *, supported by transient absorption spectra analysis. Further analysis, including time-resolved fluorescence decay measurements and time-dependent density-functional theory (TD-DFT) calculations, underscored the role of deprotonation of 's hydroxyl group in promoting the ICT process. The CIE coordination plot demonstrated wide linear emission color changes upon successive DBU additions in all solvents, while emission color precision was achieved through host-guest chemistry. Emission changes induced by DBU were reverted to the original state upon beta-cyclodextrin (β-CD) addition, with the H NMR study revealing the competition between acid-base equilibrium and host-guest complex formation as the cause of emission color change.
制备了一种荧光染料，即二噻吩共轭苯并噻唑衍生物（），使其在各种有机溶剂中具有较高的荧光发射量子产率（Φ）。通过分子内电荷转移（ICT）、酸碱平衡和主客体化学实现了其发射颜色从亮蓝色到深红色的调制。尽管它表现出较弱的溶剂化显色效应，但在大多数溶剂中，在390nm激发下，在480nm左右呈现明亮的荧光发射。在极性溶剂中，如甲醇（MeOH）、乙醇（EtOH）、N，N-二甲基甲酰胺（DMF）和二甲基亚砜（DMSO），在640nm左右出现了一个额外的ICT发射带，在DMSO中尤为强烈，产生亮绿白色发射（Φ = 0.67）。加入1,8-二氮杂双环[5,4.0]十一碳-7-烯（DBU）改变了发射特性，减少了来自局域激发（LE）态的发射并增强了ICT态发射。随着DBU的加入，发射光谱变化饱和程度随溶剂性质而变化。具有高介电常数的极性溶剂，如DMSO和DMF，在加入5当量DBU时LE态发射完全消失，产生深红色发射（Φs分别为0.53和0.48）。飞秒瞬态吸收光谱和时间分辨光致发光测量阐明了激发态动力学，揭示了在较低能量发射（640nm）处存在长寿命激发态（τ = 10.3ns），经瞬态吸收光谱分析确定为*。包括时间分辨荧光衰减测量和含时密度泛函理论（TD-DFT）计算在内的进一步分析强调了的羟基去质子化在促进ICT过程中的作用。CIE坐标图表明，在所有溶剂中连续加入DBU时发射颜色发生广泛的线性变化，而通过主客体化学实现了发射颜色的精确控制。加入β-环糊精（β-CD）后，DBU引起的发射变化恢复到原始状态，1H NMR研究表明酸碱平衡和主客体络合物形成之间的竞争是发射颜色变化的原因。
