Spectroscopic Investigation and Photophysics of a D-π-A-π-D Type Styryl Pyrazine Derivative
作者:Samy A. El-Daly、Khalid A. Alamry
DOI:10.1007/s10895-015-1698-7
日期:2016.1
E,E-2,5-bis(3,4-dimethoxystyryl)pyrazine (BDSP) has been prepared by aldol condensation between 2,5-dimethypyrazine and 3,4-dimthoxybenzaldehyde and characterized by IR, 1H NMR, 13C NMR and X-ray crystallography. The electronic absorption and emission properties of BDSP were studied in different solvents. BDSP displays a strong solvatochromic effect of the emission spectrum that is reflected by large red shifts of its fluorescence emission maximum on increasing the solvent polarity, indicating a large change in dipole moment of BDSP upon excitation due to photoinduced intramolecular charge transfer (PICT). Excited state intermolecular hydrogen bonding affects the energy of emission spectrum and fluorescence quantum yield of BDSP dye. The dye solutions (1 × 10−4 M) in DMSO, DMF, CH3CN and dioxane give laser emission in green region upon excitation by a 337.1 nm nitrogen pulse (λ = 337 nm). The tuning range, gain coefficient (α), emission cross – section (σe) and half-life energy (E1/2) has been determined. Ground and electronic excited states geometric optimization were performed using density functional theory (DFT) and time-dependent density functional theory (TD-DFT), respectively. A DFT natural bond analysis complemented the ICT. BDSP dye displays fluorescence quenching by colloidal silver nanoparticles (AgNPs). The fluorescence data reveal that radiative and non-radiative energy transfer play a major role in the fluorescence quenching mechanism.
2,5 二甲基吡嗪和 3,4 二甲基苯甲醛通过醛醇缩合反应制备了 E,E-2,5-双(3,4-二甲氧基苯乙烯基)吡嗪(BDSP),并通过红外光谱、1H NMR、13C NMR 和 X 射线晶体学对其进行了表征。研究了 BDSP 在不同溶剂中的电子吸收和发射特性。BDSP 的发射光谱具有很强的溶解变色效应,这体现在溶剂极性增加时,其荧光发射最大值发生了很大的红移,这表明由于光诱导分子内电荷转移(PICT),BDSP 在激发时偶极矩发生了很大变化。激发态分子间氢键影响 BDSP 染料的发射光谱能量和荧光量子产率。在 DMSO、DMF、CH3CN 和二噁烷中的染料溶液(1 × 10-4 M)在 337.1 nm 氮脉冲(λ = 337 nm )的激发下发出绿色区域的激光。已确定了调谐范围、增益系数(α)、发射截面(σe)和半衰期能量(E1/2)。分别使用密度泛函理论(DFT)和时间相关密度泛函理论(TD-DFT)对基态和电子激发态进行了几何优化。DFT 自然键分析对 ICT 进行了补充。胶体银纳米粒子(AgNPs)可淬灭 BDSP 染料的荧光。荧光数据揭示了辐射和非辐射能量转移在荧光淬灭机制中的主要作用。