本文選題：液相 + 激發(fā)態(tài)�。� 參考：《吉林大學(xué)》2016年博士論文

【摘要】：分子激發(fā)態(tài)超快動(dòng)力學(xué)過(guò)程一直是原子與分子物理領(lǐng)域關(guān)注的熱點(diǎn)問(wèn)題。眾所周知,自然環(huán)境中大多數(shù)的化學(xué)現(xiàn)象和生命活動(dòng)都是在液相體系下進(jìn)行的,研究液相體系特別是液相中大分子復(fù)雜體系對(duì)于人們了解自然界中基本光物理、光化學(xué)過(guò)程的機(jī)制非常重要。值得注意的是,許多重要的光物理、光化學(xué)過(guò)程都涉及分子的激發(fā)態(tài),例如生物分子中廣泛存在的激發(fā)態(tài)質(zhì)子轉(zhuǎn)移、電荷轉(zhuǎn)移等,這就為研究液相中大分子復(fù)雜體系的激發(fā)態(tài)超快過(guò)程賦予了特殊的意義。在本文中,我們應(yīng)用飛秒瞬態(tài)吸收光譜實(shí)驗(yàn)技術(shù)結(jié)合含時(shí)密度泛函理論計(jì)算方法針對(duì)幾種液相體系的激發(fā)態(tài)分子內(nèi)超快動(dòng)力學(xué)過(guò)程進(jìn)行了研究。主要內(nèi)容概括如下:(1)應(yīng)用密度泛函/含時(shí)密度泛函(DFT/TDDFT)理論方法針對(duì)Salicylaldehyde(SA)分子的激發(fā)態(tài)分子內(nèi)質(zhì)子轉(zhuǎn)移過(guò)程(ESIPT)進(jìn)行了研究。結(jié)果表明,SA分子在被激發(fā)到第一電子激發(fā)態(tài)(S1)后會(huì)發(fā)生ESIPT現(xiàn)象,證實(shí)了Stock關(guān)于SA分子在環(huán)己烷(CHX)溶劑中超快實(shí)驗(yàn)的推測(cè)[1],并且揭示了SA分子特殊的單熒光特性來(lái)源于其S1態(tài)只有一個(gè)異構(gòu)化的穩(wěn)定結(jié)構(gòu),即只存在酮式(keto*)結(jié)構(gòu),烯醇式結(jié)構(gòu)(enol*)在S1態(tài)并不存在。此外,計(jì)算結(jié)果還說(shuō)明了由分子內(nèi)電荷再分布導(dǎo)致的羰基氧電負(fù)性變化是SA分子發(fā)生ESIPT現(xiàn)象的原因。(2)我們對(duì)1-hydroxypyrene-2-carbaldehyde(HP)分子及其衍生物1-methoxypyrene-2-carbaldehyde(MP)分子在環(huán)己烷(CHX)溶劑中的超快過(guò)程進(jìn)行了實(shí)驗(yàn)與理論研究。穩(wěn)態(tài)光譜實(shí)驗(yàn)表明,MP分子有明顯的熒光屬性而HP分子卻具有無(wú)熒光特性。應(yīng)用飛秒瞬態(tài)吸收光譜實(shí)驗(yàn)方法觀測(cè)了HP分子與MP分子的激發(fā)態(tài)超快動(dòng)力學(xué)過(guò)程。實(shí)驗(yàn)結(jié)果擬合表明,HP分子存在兩個(gè)超快過(guò)程,分別為激發(fā)態(tài)分子內(nèi)質(zhì)子轉(zhuǎn)移過(guò)程(ESIPT)與系間竄越過(guò)程(ISC);而MP分子只有一個(gè)溶質(zhì)—溶劑相互的超快過(guò)程。在此基礎(chǔ)上,采用DFT/TDDFT方法對(duì)HP分子進(jìn)行了理論計(jì)算,獲得了勢(shì)能曲線、紅外光譜等相關(guān)信息,證實(shí)了HP分子被激發(fā)到S1態(tài)后先經(jīng)歷ESIPT過(guò)程,隨后發(fā)生ISC過(guò)程。結(jié)合飛秒瞬態(tài)吸收光譜與TDDFT理論計(jì)算結(jié)果,發(fā)現(xiàn)ISC過(guò)程的發(fā)生是HP分子熒光猝滅的原因。(3)應(yīng)用高壓瞬態(tài)吸收光譜技術(shù)結(jié)合DFT/TDDFT理論方法,研究了高壓對(duì)香豆素510(C510)分子在乙腈(ACN)溶劑中激發(fā)態(tài)扭轉(zhuǎn)分子內(nèi)電荷轉(zhuǎn)移(TICT)過(guò)程的影響,壓力范圍是常壓到0.3 GPa。通過(guò)對(duì)C510體系常壓下的分子性質(zhì)進(jìn)行計(jì)算,我們獲得了基態(tài)、第一電子激發(fā)態(tài)(S1)態(tài)的幾何構(gòu)型以及電荷分布,證明了該分子被激發(fā)到S1態(tài)后會(huì)發(fā)生TICT過(guò)程。在此基礎(chǔ)上,應(yīng)用高壓瞬態(tài)吸收方法觀測(cè)了壓力對(duì)C510分子TICT過(guò)程的影響。結(jié)果表明,隨著壓力的提高相應(yīng)的溶劑粘度系數(shù)也增大,但是C510分子TICT過(guò)程卻反常地變快,并伴隨著熒光壽命的變短。通過(guò)實(shí)驗(yàn)與理論研究,本文把上述新穎現(xiàn)象產(chǎn)生的原因分別歸屬于C510分子被激發(fā)后基團(tuán)的反轉(zhuǎn)(使分子整體更加趨于平面)以及壓力導(dǎo)致的基態(tài)與激發(fā)態(tài)之間能隙變小。
[Abstract]:The ultrafast kinetic process of molecular excited states has always been a hot issue in the field of atomic and molecular physics. It is well known that most of the chemical phenomena and life activities in the natural environment are carried out under the liquid phase system. The study of the liquid phase system, especially the large molecular complex in the liquid phase, has been used to understand the basic optical physics in nature, The mechanism of photochemical process is very important. It is worth noting that many important photophysical and photochemical processes involve the excited state of molecules, such as the excited state proton transfer and charge transfer, which are widely existed in the biomolecules. This has given special significance to the study of the excite ultrafast process in the complex system of large molecules in the liquid phase. In this paper, we use femtosecond transient absorption spectroscopy (femtosecond transient absorption spectroscopy) technique and time-dependent density functional theory to study the intramolecular ultrafast dynamic processes of several liquid phase systems. The main contents are as follows: (1) the application of density functional / time density functional (DFT/TDDFT) theory to Salicylaldehyde (SA) molecules The intron transfer process (ESIPT) of the excited state molecules (ESIPT) has been studied. The results show that the ESIPT phenomenon occurs after the SA molecule is excited to the first electron excited state (S1), which confirms the Stock about the ultra fast experiment of the SA molecule in the cyclohexane (CHX) solvent and reveals that the special single fluorescence characteristic of the SA molecule comes from the only one of the S1 states. The stable structure of isomerization is only a ketone (keto*) structure and the enol structure (enol*) does not exist in the S1 state. In addition, the results also show that the negative changes in carbonyl oxygen caused by the redistribution of intramolecular charge redistribution are the reasons for the ESIPT phenomenon of the SA molecule. (2) we are on the 1-hydroxypyrene-2-carbaldehyde (HP) molecule and its derivatives. The ultrafast process of 1-methoxypyrene-2-carbaldehyde (MP) molecule in the solvent of cyclohexane (CHX) has been studied experimentally and theoretically. The steady-state spectral experiments show that the MP molecules have obvious fluorescence properties while the HP molecules have no fluorescence characteristics. The ultrafast dynamics of the excited states of HP and MP molecules are observed by the experimental method of femtosecond transient absorption spectroscopy. The experimental results show that there are two ultrafast processes in the HP molecule, which are the transition process of the excited state intramolecular endoplasmic reticulum (ESIPT) and intersystem channeling (ISC), and the MP molecule has only one solute solvent super fast process. On this basis, the DFT/TDDFT method is used to calculate the HP molecule, and the potential energy curve is obtained. The infrared spectrum and other related information confirmed that the HP molecule was excited to the S1 state after the ESIPT process and then the ISC process. Combining the femtosecond transient absorption spectrum and the TDDFT theoretical calculation, it was found that the occurrence of the ISC process was the cause of the fluorescence quenching of HP molecules. (3) the application of high pressure transient absorption spectroscopy combined with the DFT/TDDFT theoretical method. The effect of high pressure on the torsional intramolecular charge transfer (TICT) process of the excited state of coumarin 510 (C510) molecule in acetonitrile (ACN) solvent. The pressure range is calculated by the atmospheric pressure to 0.3 GPa. by the molecular properties under the atmospheric pressure of the C510 system. We have obtained the ground state, the geometry configuration of the first electron excited state (S1) state and the charge distribution. On the basis of the high pressure transient absorption method, the effect of pressure on the TICT process of C510 molecule is observed by high pressure transient absorption. The result shows that the corresponding viscosity coefficient of the solvent increases with the increase of pressure, but the TICT process of the C510 molecule becomes faster and faster, with the shorter fluorescence lifetime. Through real time, the C510 molecule has a short time of the C510. In the laboratory and theory study, the causes of the above novel phenomena are attributed to the reversal of the group after the C510 molecule is excited (making the whole molecule more flat) and the gap between the ground state and the excited state caused by the pressure is smaller.

【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：O561

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本文編號(hào)：1863321