硝基多環(huán)芳烴及其衍生物激發(fā)態(tài)光物理、光化學反應研究
發(fā)布時間：2018-12-31 11:08
【摘要】：硝基多環(huán)芳烴屬于持久性有機污染物,形成于不完全燃燒過程以及多環(huán)芳烴在氣相中的反應,硝基多環(huán)芳烴的致癌性和致突變性比多環(huán)芳烴高十到十萬倍。光降解是硝基多環(huán)芳烴在自然界的主要衰減通道�；鶓B(tài)硝基多環(huán)芳烴受光激發(fā)后有兩條衰減路徑,其一為發(fā)生超快系間竄越到達激發(fā)三重態(tài),其二為發(fā)生光解離生成芳氧自由基。最低激發(fā)三重態(tài)的硝基多環(huán)芳烴有納秒至微秒量級的壽命,較長的壽命使其發(fā)生雙分子或多分子反應成為可能,常見的反應類型有能量傳遞、質子化、電子轉移反應、奪氫反應等。本論文利用納秒瞬態(tài)吸收光譜、納秒時間分辨共振拉曼光譜技術,輔以含時密度泛函理論、完全活化空間自洽場理論計算方法,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)的最低激發(fā)三重態(tài)在有機溶劑和含水溶劑中的性質以及能量傳遞、質子化、電子轉移反應、奪氫反應的反應活性,探究了光化學反應中間體的形成機理。獲得主要結論如下:(1)首次觀測到了三重態(tài)2Me1NN發(fā)生分子內氫轉移反應,捕捉到了反應中間體并指認其結構。觀測到2-甲基-1-萘氧自由基,動力學實驗結果證實其并非形成于T_1態(tài)2Me1NN。動力學實驗結果表明T_1態(tài)2Me1NN和H2O的反應是三級反應,因而推測反應機理為T_1態(tài)2Me1NN和H2O通過氫鍵形成復合物,發(fā)生質子轉移,然后電子轉移形成奪氫后的自由基,接著在另一個H2O分子的協(xié)助下脫質子形成自由基陰離子。(2)1Me4NN、MeONN屬于電子“推拉”結構的分子。甲氧基與甲基供電子能力強弱使MeONN的硝基電子密度更大,這影響了1Me4NN、MeONN的三重態(tài)在質子化、電子轉移反應、奪氫反應中的反應活性,動力學研究獲得了這些反應的速率常數(shù)。實驗結果顯示,三重態(tài)1Me4NN更容易發(fā)生電子轉移反應,而三重態(tài)MeONN更容易質子化。(3)三重態(tài)2NF在不同溶劑中展現(xiàn)了不同的性質。在非極性溶劑中主要存在T_1態(tài),并且T_1態(tài)勢能面與解離態(tài)存在交叉點,能沿著解離通道發(fā)生解離,使三重態(tài)壽命大大縮短。在極性非質子溶劑中,T_1態(tài)、T2態(tài)能同時存在。質子溶劑中,羥基的氫能與T2態(tài)2NF中硝基的氧形成氫鍵,使T2態(tài)長波長吸收帶的吸收強度增加、三重態(tài)壽命更長。
[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.
【學位授予單位】：浙江理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O644.1;O625.611
本文編號：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.
【學位授予單位】：浙江理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O644.1;O625.611
【共引文獻】
相關博士學位論文 前3條
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相關碩士學位論文 前1條
1 周強;針對復雜等截面芯軸的環(huán)形編織絲束軌跡預測算法及其實現(xiàn)[D];浙江理工大學;2017年
，本文編號：2396488
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