A group of novel 2-aryl imidazole derivatives were synthesized and characterized by NMR spectra, X-ray, mass and CHN analysis. An excited state intramolecular proton transfer (ESIPT) process in hydroxy imidazoles (dmip and dmtip) have been studied using emission spectroscopy and it was detected that the two distinct ground state rotamers of I and II are responsible for the normal and the tautomer emission respectively. In hydrocarbon solvent, the tautomer emission predominates over the normal emission for both dmip and dmtip. This reveal that rotamer II is responsible for the tautomer emission and it is stabler than rotamer I which causes the normal emission. In alcoholic solvent like ethanol, a dramatic enhancement of normal emission is observed which was due to increased solvation, the more polar rotamer I become stabler than rotamer II. In dioxane—water mixtures it is observed that the addition of water inhibits the ESIPT process due to the formation of the intermolecular hydrogen bonding involving water. DFT calculations on energy, dipole moment, charge distribution of the rotamers in the ground and excited states of the imidazole derivatives were performed and discussed. PES calculation indicates that the energy barrier for the interconversion of two rotamers is too high in the excited state than the ground state.
合成了一组新型2-芳基
咪唑衍
生物,并通过NMR谱、X射线、质量和CHN分析进行了表征。使用发射光谱研究了羟基
咪唑(dmip 和 dmtip)中的激发态分子内质子转移(ESI
PT)过程,并检测到 I 和 II 两种不同的基态旋转异构体分别负责正常和互变异构体发射。在烃溶剂中,对于 dmip 和 dmtip,互变异构体发射比正常发射占主导地位。这表明旋转异构体 II 负责互变异构体发射,并且它比导致正常发射的旋转异构体 I 更稳定。在
乙醇等醇溶剂中,观察到正常发射的显着增强,这是由于溶剂化增加,极性更强的旋转异构体 I 变得比旋转异构体 II 更稳定。在
二恶烷-
水混合物中,观察到添加
水会抑制 ESI
PT 过程,因为涉及
水的分子间氢键的形成。对
咪唑衍
生物的能量、偶极矩、基态和激发态旋转异构体的电荷分布进行了DFT计算并进行了讨论。 PES计算表明,激发态下两个旋转异构体相互转化的能垒比基态高。