Al-Soliemy Amerah M, Osman Osman I, Hussein Mahmoud A, Asiri Abdullah M, El-Daly Samy A
Department of Chemistry, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah, 21589, Saudi Arabia.
Chemistry Department, Faculty of Science, Khartoum University, P.O. Box 321, 11111, Khartoum, Sudan.
J Fluoresc. 2016 Jul;26(4):1199-209. doi: 10.1007/s10895-016-1802-7. Epub 2016 Apr 15.
E,E-2,5-bis[2-(3-pyridyl)ethenyl]pyrazine (BPEP) has been prepared by aldol condensation between 2,5-dimethylpyrazine and pyridine-3-carboxaldehyde. It is characterized by IR, (1)H NMR, and (13)C NMR. The electronic absorption and emission properties of BPEP were studied in different solvents. BPEP displays a slight solvatochromic effect of the absorption and emission spectrum, indicating a small change in dipole moment of BPEP upon excitation. The dye solutions (1 × 10(-4) M) in CHCl3, EtOH and dioxane give laser emission in blue region upon excitation by a 337.1 nm nitrogen pulse (λ = 337 nm). The tuning range, gain coefficient (α) and emission cross - section (σe) have been determined. Ground and excited states electronic geometric optimizations were performed using density functional theory (DFT) and time-dependent density functional theory (TD-DFT), respectively. A DFT natural bond analysis complemented the ICT. The simulated maximum absorption and emission wavelengths are in line the observed ones in trend, and are proportionally red-shifted with the increase of the solvent polarity. The stability, hardness and electrophilicity of BPEP in different solvents were correlated with the polarity of the elected solvents. BPEP 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.
E,E-2,5-双[2-(3-吡啶基)乙烯基]吡嗪（BPEP）通过2,5-二甲基吡嗪与吡啶-3-甲醛之间的羟醛缩合反应制备而成。通过红外光谱、¹H核磁共振和¹³C核磁共振对其进行了表征。研究了BPEP在不同溶剂中的电子吸收和发射特性。BPEP在吸收和发射光谱上表现出轻微的溶剂化显色效应，表明激发时BPEP的偶极矩变化较小。在337.1 nm氮脉冲（λ = 337 nm）激发下，BPEP在氯仿、乙醇和二氧六环中的染料溶液（1×10⁻⁴ M）在蓝色区域产生激光发射。测定了调谐范围、增益系数（α）和发射截面（σe）。分别使用密度泛函理论（DFT）和含时密度泛函理论（TD-DFT）对基态和激发态电子几何结构进行了优化。DFT自然键分析对分子内电荷转移进行了补充。模拟的最大吸收和发射波长在趋势上与观测值一致，并且随着溶剂极性的增加成比例地红移。BPEP在不同溶剂中的稳定性、硬度和亲电性与所选溶剂的极性相关。BPEP染料表现出被胶体银纳米颗粒（AgNPs）荧光猝灭的现象。荧光数据表明，辐射和非辐射能量转移在荧光猝灭机制中起主要作用。
