硝基多环芳烃及其衍生物激发态光物理、光化学反应研究
发布时间：2018-12-31 11:08
【摘要】：硝基多环芳烃属于持久性有机污染物,形成于不完全燃烧过程以及多环芳烃在气相中的反应,硝基多环芳烃的致癌性和致突变性比多环芳烃高十到十万倍。光降解是硝基多环芳烃在自然界的主要衰减通道。基态硝基多环芳烃受光激发后有两条衰减路径,其一为发生超快系间窜越到达激发三重态,其二为发生光解离生成芳氧自由基。最低激发三重态的硝基多环芳烃有纳秒至微秒量级的寿命,较长的寿命使其发生双分子或多分子反应成为可能,常见的反应类型有能量传递、质子化、电子转移反应、夺氢反应等。本论文利用纳秒瞬态吸收光谱、纳秒时间分辨共振拉曼光谱技术,辅以含时密度泛函理论、完全活化空间自洽场理论计算方法,研究了2-甲基-1-硝基萘(2Me1NN)、1-甲基-4-硝基萘(1Me4NN)、1-甲氧基-4-硝基萘(MeONN)、2-硝基芴(2NF)的最低激发三重态在有机溶剂和含水溶剂中的性质以及能量传递、质子化、电子转移反应、夺氢反应的反应活性,探究了光化学反应中间体的形成机理。获得主要结论如下:(1)首次观测到了三重态2Me1NN发生分子内氢转移反应,捕捉到了反应中间体并指认其结构。观测到2-甲基-1-萘氧自由基,动力学实验结果证实其并非形成于T_1态2Me1NN。动力学实验结果表明T_1态2Me1NN和H2O的反应是三级反应,因而推测反应机理为T_1态2Me1NN和H2O通过氢键形成复合物,发生质子转移,然后电子转移形成夺氢后的自由基,接着在另一个H2O分子的协助下脱质子形成自由基阴离子。(2)1Me4NN、MeONN属于电子“推拉”结构的分子。甲氧基与甲基供电子能力强弱使MeONN的硝基电子密度更大,这影响了1Me4NN、MeONN的三重态在质子化、电子转移反应、夺氢反应中的反应活性,动力学研究获得了这些反应的速率常数。实验结果显示,三重态1Me4NN更容易发生电子转移反应,而三重态MeONN更容易质子化。(3)三重态2NF在不同溶剂中展现了不同的性质。在非极性溶剂中主要存在T_1态,并且T_1态势能面与解离态存在交叉点,能沿着解离通道发生解离,使三重态寿命大大缩短。在极性非质子溶剂中,T_1态、T2态能同时存在。质子溶剂中,羟基的氢能与T2态2NF中硝基的氧形成氢键,使T2态长波长吸收带的吸收强度增加、三重态寿命更长。
[Abstract]:Nitro polycyclic aromatic hydrocarbons (NPAs) are persistent organic pollutants formed during incomplete combustion and the reactions of PAHs in gas phase. The carcinogenicity and mutagenicity of NPAs are 10 to 100 times higher than that of PAHs. Photodegradation is the main attenuation channel of nitropolycyclic aromatic hydrocarbons (NPAHs) in nature. Ground state nitro polycyclic aromatic hydrocarbons (NPAHs) have two decay paths after photoexcitation, one is the transition between ultrafast systems to the excited triplet, the other is the generation of aromatic oxygen radicals by photodissociation. The lowest excited triplet nitro polycyclic aromatic hydrocarbons have a lifetime of nanosecond to microsecond order of magnitude, and the long lifetime makes it possible for them to undergo bimolecular or multimolecular reactions. The common types of reactions are energy transfer, protonation, electron transfer reactions. A hydrogen capture reaction, etc. Using nanosecond transient absorption spectroscopy, nanosecond time-resolved resonance Raman spectroscopy, time-dependent density functional theory and fully activated space self-consistent field theory, 2-methyl-1-nitronaphthalene (2Me1NN) has been studied. The properties of the lowest excited triplet of 1-methyl-4-nitronaphthalene (1Me4NN), 1-methoxy-4-nitronaphthalene (MeONN), 2-nitrofluorene (2NF) in organic and aqueous solvents, as well as the energy transfer, protonation, electron transfer reactions, The reaction activity of hydrogen capture reaction and the formation mechanism of photochemical intermediates were investigated. The main conclusions are as follows: (1) the intramolecular hydrogen transfer reaction of triplet 2Me1NN was observed for the first time, the intermediate was captured and its structure was identified. The 2-methyl-1-naphthoxy radical was observed, and the kinetic results confirmed that it was not formed in the T-1 state 2Me1NN. The kinetic results show that the reaction of T _ 1 2Me1NN and H _ 2O is a third-order reaction. Therefore, the mechanism of the reaction is that 2Me1NN and H _ 2O in T _ (1) state form a complex by hydrogen bond, and then the electron transfer forms the free radical after hydrogen capture. Then, with the help of another H2O molecule, the free radical anions are formed. (2) 1Me4NNNNNMeONN belongs to the electronic "push-pull" structure of the molecule. The electron density of nitro group in MeONN is higher than that of methoxy group and methyl group, which affects the activity of triplet state of 1Me4NN MeONN in protonation, electron transfer reaction and hydrogen capture reaction. The rate constants of these reactions have been obtained by kinetic study. The experimental results show that triplet 1Me4NN is more prone to electron transfer reaction and triplet MeONN is easier to protonate. (3) triplet 2NF exhibits different properties in different solvents. In nonpolar solvents, there is mainly a T _ S _ 1 state, and there exists a crossing point between the T _ 1 potential energy surface and the dissociation state, which can be dissociated along the dissociation channel, thus shortening the triplet life greatly. In polar non-proton solvents, the T _ S _ 1 and T _ 2 states can exist at the same time. In proton solvent, the hydrogen energy of hydroxyl group forms a hydrogen bond with nitro oxygen in T2 state 2NF, which increases the absorption intensity of the long wavelength absorption band of T2 state and prolongs the triplet lifetime.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O644.1;O625.611
本文编号：2396488
[Abstract]:Nitro polycyclic aromatic hydrocarbons (NPAs) are persistent organic pollutants formed during incomplete combustion and the reactions of PAHs in gas phase. The carcinogenicity and mutagenicity of NPAs are 10 to 100 times higher than that of PAHs. Photodegradation is the main attenuation channel of nitropolycyclic aromatic hydrocarbons (NPAHs) in nature. Ground state nitro polycyclic aromatic hydrocarbons (NPAHs) have two decay paths after photoexcitation, one is the transition between ultrafast systems to the excited triplet, the other is the generation of aromatic oxygen radicals by photodissociation. The lowest excited triplet nitro polycyclic aromatic hydrocarbons have a lifetime of nanosecond to microsecond order of magnitude, and the long lifetime makes it possible for them to undergo bimolecular or multimolecular reactions. The common types of reactions are energy transfer, protonation, electron transfer reactions. A hydrogen capture reaction, etc. Using nanosecond transient absorption spectroscopy, nanosecond time-resolved resonance Raman spectroscopy, time-dependent density functional theory and fully activated space self-consistent field theory, 2-methyl-1-nitronaphthalene (2Me1NN) has been studied. The properties of the lowest excited triplet of 1-methyl-4-nitronaphthalene (1Me4NN), 1-methoxy-4-nitronaphthalene (MeONN), 2-nitrofluorene (2NF) in organic and aqueous solvents, as well as the energy transfer, protonation, electron transfer reactions, The reaction activity of hydrogen capture reaction and the formation mechanism of photochemical intermediates were investigated. The main conclusions are as follows: (1) the intramolecular hydrogen transfer reaction of triplet 2Me1NN was observed for the first time, the intermediate was captured and its structure was identified. The 2-methyl-1-naphthoxy radical was observed, and the kinetic results confirmed that it was not formed in the T-1 state 2Me1NN. The kinetic results show that the reaction of T _ 1 2Me1NN and H _ 2O is a third-order reaction. Therefore, the mechanism of the reaction is that 2Me1NN and H _ 2O in T _ (1) state form a complex by hydrogen bond, and then the electron transfer forms the free radical after hydrogen capture. Then, with the help of another H2O molecule, the free radical anions are formed. (2) 1Me4NNNNNMeONN belongs to the electronic "push-pull" structure of the molecule. The electron density of nitro group in MeONN is higher than that of methoxy group and methyl group, which affects the activity of triplet state of 1Me4NN MeONN in protonation, electron transfer reaction and hydrogen capture reaction. The rate constants of these reactions have been obtained by kinetic study. The experimental results show that triplet 1Me4NN is more prone to electron transfer reaction and triplet MeONN is easier to protonate. (3) triplet 2NF exhibits different properties in different solvents. In nonpolar solvents, there is mainly a T _ S _ 1 state, and there exists a crossing point between the T _ 1 potential energy surface and the dissociation state, which can be dissociated along the dissociation channel, thus shortening the triplet life greatly. In polar non-proton solvents, the T _ S _ 1 and T _ 2 states can exist at the same time. In proton solvent, the hydrogen energy of hydroxyl group forms a hydrogen bond with nitro oxygen in T2 state 2NF, which increases the absorption intensity of the long wavelength absorption band of T2 state and prolongs the triplet lifetime.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O644.1;O625.611
【共引文献】
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2 吴利伟;四步法三维编织复合材料弯曲疲劳性质及损伤演化有限元分析[D];东华大学;2014年
3 王睿;连续碳纤维表面金属化及其复合材料电磁屏蔽性能研究[D];天津大学;2012年
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