本文選題：雙線態(tài) + 共軛效應(yīng)　； 參考：《吉林大學(xué)》2017年碩士論文

【摘要】：穩(wěn)定自由基因為其單電子的穩(wěn)定存而使得其具有很多獨特的性質(zhì),如順磁性,氧化還原電位低,能隙窄等特點。因此,自1900年第一例穩(wěn)定自由基報道以來,這類分子得到了廣泛研究。由于自由基單電子的存在,電子的躍遷在本質(zhì)上與閉殼分子有所區(qū)別,表現(xiàn)為無論是激發(fā)態(tài)還是基態(tài),自由基分子都表現(xiàn)出雙線態(tài)的特點。自由基單電子占據(jù)軌道(SOMO)上只有一個電子,所以無論是SOMO和最低未占據(jù)軌道(LUMO)還是雙電子最高占據(jù)軌道(HOMO)和SOMO之間的躍遷,都是完全自旋允許的。因此研究這種區(qū)別于普通熒光(來源于單線態(tài)激子的輻射躍遷)和磷光(源自三線態(tài)激子的輻射躍遷)的雙線態(tài)發(fā)光機制,不僅具有重要的科學(xué)意義,同時也為有機發(fā)光領(lǐng)域拓展了新的思路。然而,目前報道具有發(fā)光性質(zhì)的自由基非常罕見,此外自由基的發(fā)光效率低,穩(wěn)定性差。因此,如何提高自由基的穩(wěn)定性和發(fā)光效率這一問題亟待解決。一般來說,增加共軛能夠提高發(fā)光分子的穩(wěn)定性和發(fā)光效率。因此,本文中,我們通過給一種穩(wěn)定的發(fā)光中性自由基——全氯代三苯甲基自由基(PTM)——連接給、拉電子基團(tuán),研究這兩種方法增加共軛效應(yīng)對自由基的穩(wěn)定性和發(fā)光性質(zhì)的影響,并期待找到提高自由基的穩(wěn)定性和發(fā)光效率的途徑。首先,我們基于PTM合成了連接拉電子基團(tuán)二苯甲酮(DPK)和氰基二苯基乙烯(CPE)的自由基PTM-DPK,PTM-CPE,研究利用拉電子基團(tuán)增加共軛對自由基熒光和穩(wěn)定性的影響。通過DFT理論計算,我們發(fā)現(xiàn)連接拉電子基團(tuán)能夠增加共軛。通過溶劑化效應(yīng),我們發(fā)現(xiàn)PTM-DPK,PTM-CPE和PTM一樣,隨著溶劑極性的增強,光譜峰位置不變。說明連接拉電子基團(tuán)的自由基和PTM一樣屬于局域態(tài)發(fā)光,同時我們發(fā)現(xiàn)相較于PTM,PTM-DPK和PTM-CPE的熒光量子效率沒有顯著變化。說明通過連接拉電子基團(tuán)增加共軛不能提高自由基的熒光量子效率。但是,通過研究PTM-DPK,PTM-CPE的光穩(wěn)定性,我們發(fā)現(xiàn)PTM-DPK,PTM-CPE的穩(wěn)定性有較大的提高,說明拉電子基團(tuán)能夠增加自由基的光穩(wěn)定性。通過電化學(xué)研究并對比自由基380nm的特征吸收峰,我們發(fā)現(xiàn)PTM系列的氧化電位都很高,并且拉電子基團(tuán)對氧化和還原電位的影響不大,這是因為三苯甲基和氯原子引起的強的空間位阻效應(yīng)作用的結(jié)果。接著我們又研究了不同給電子能力的基團(tuán)對其熒光和穩(wěn)定性的影響。我們合成了連接給電子基團(tuán)甲硫基苯、咔唑萘、3,5-二咔唑苯基自由基PTM-PSM、PTM-Cz N、PTM-PDCz三個連接不同給電子能力基團(tuán)的自由基分子,通過DFT理論計算,我們發(fā)現(xiàn)給電子基團(tuán)沒有增加共軛效應(yīng),但是通過溶劑化效應(yīng)研究發(fā)現(xiàn)連接給電子基團(tuán)的自由基屬于電荷轉(zhuǎn)移發(fā)光,并且DFT計算表明電荷轉(zhuǎn)移是從給體的HOMO到三苯甲基自由基的SOMO的躍遷。相較于PTM,PTM-PSM,PTM-Cz N,PTM-PDCz的熒光量子效率明顯提高,比如PTM-Cz N在環(huán)己烷中的發(fā)光效率高達(dá)0.54,比PTM的0.016高了34倍。這說明連接電子給體能夠提高自由基的熒光量子效率。同時我們發(fā)現(xiàn)PTM-PSM,PTM-Cz N,PTM-PDCz的穩(wěn)定性也有巨大的提高,這說明連接給體不僅能有效提高自由基的熒光量子效率,而且也能提高自由基的穩(wěn)定性。因此給電子基團(tuán)是設(shè)計高穩(wěn)定性高熒光量子效率的一個策略。通過電化學(xué)和理論計算研究,我們發(fā)現(xiàn)連接給電子基團(tuán)的自由基表現(xiàn)出HOMO-SOMO反轉(zhuǎn)的奇特性質(zhì),表現(xiàn)為HOMO能級位于SOMO能級之上。由于空間位阻的原因,SOMO的電位變化很小,所以如果HOMO(來自于給電子基團(tuán))能量高,就可能位于SOMO之上,并且HOMO的能量越高,SOMO與HOMO的能量差越大。因此不同的給電子基團(tuán)使得SOMO的位置位于HOMO下面的程度不同,PTM-PSM在HOMO之下,PTM-Cz N在HOMO-1之下,PTM-PDCz在HOMO-3之下,同時對應(yīng)的穩(wěn)定性增加程度與SOMO位置對應(yīng),SOMO越往下,穩(wěn)定性越高。HOMO-SOMO的反轉(zhuǎn),使得自由基分子的電子排布違反了構(gòu)造原理(Aufbau Principle),出現(xiàn)了和部分過渡態(tài)金屬,量子點類似的結(jié)果,這在有機分子中非常少見。通過研究HOMO-SOMO的反轉(zhuǎn)必然能夠增加人們對自由基的進(jìn)一步理解。同時HOMO-SOMO的反轉(zhuǎn)的D-A自由基的熒光量子效率,穩(wěn)定性都大大提高。因此,這也是設(shè)計高熒光量子效率,高穩(wěn)定性的自由基分子一種可行的策略。
[Abstract]:The stable free gene has many unique properties, such as paramagnetic, low oxidation-reduction potential, narrow energy gap, and so on. Therefore, since the first case of stable free radicals in 1900, this kind of molecule has been widely studied. Because of the existence of free radical mono electrons, the transition of electrons is essentially closed to the shell. The molecules are different, showing that both the excited state and the ground state show the characteristics of the double state. The free radical mono electrons occupy only one electron on the orbit (SOMO), so the transition between the SOMO and the lowest unoccupied orbit (LUMO) or the double electron highest occupying orbit (HOMO) and SOMO is fully spin allowed. Therefore, it is not only of great scientific significance but also a new way of thinking for the field of organic luminescence. However, it is reported that the free radicals with the properties of luminescence are very important. In addition, the luminescence efficiency of the free radicals is low and the stability is poor. Therefore, the problem of how to improve the stability and luminous efficiency of the free radicals is urgent. In general, the addition of conjugation can improve the stability and luminous efficiency of the luminescent molecules. Therefore, in this paper, we give a stable luminescent neutral free radical - Total chlorination three Benzyl free radical (PTM) - connect to, pull electron group, study these two methods to increase the effect of conjugation effect on the stability and luminescence properties of free radicals, and expect to find ways to improve the stability and luminescence efficiency of free radicals. First, we synthesized two benzophenone (DPK) and two cyanyl benzene based on PTM. The free radical PTM-DPK, PTM-CPE of ethylene (CPE) is used to study the effect of increasing conjugation on free radical fluorescence and stability. Through the calculation of DFT theory, we find that the connecting pull electron group can increase the conjugation. Through the solvent effect, we find that PTM-DPK, PTM-CPE and PTM are the same as the polarity of the solvent, the peak position of the spectrum. It is shown that the free radicals connected to the electron group are the same as the local state luminescence, and we found that the fluorescence quantum efficiency of the PTM-DPK and PTM-CPE has no significant change in the phase of the PTM, PTM-DPK and PTM-CPE. It is indicated that the fluorescence quantum efficiency of the free radical can not be enhanced by the addition of the electron group to the electron group. However, the optical stability of the PTM-DPK, PTM-CPE is studied. Qualitatively, we found that the stability of PTM-DPK and PTM-CPE has been greatly improved, indicating that the electron group can increase the photostability of the free radical. Through the electrochemical study and comparison of the characteristic absorption peaks of the free radical 380nm, we found that the oxidation potential of the PTM series is very high and the effect of the pullant group on the oxidation and reducing potential is little. Because of the strong steric hindrance effect of three benzyl methyl and chlorine atoms, we then studied the effects of groups with different electron giving capacity on their fluorescence and stability. We synthesized three connections that are connected to the electron group methionyl benzene, carbazole naphthalene, 3,5- two carbazole phenyl free radical PTM-PSM, PTM-Cz N, PTM-PDCz. The free radical molecules for the electronic group are calculated by the DFT theory. We find that the electron group does not increase the conjugation effect, but the free radical connected to the electronic group is attributed to the charge transfer luminescence through the solvation effect, and the DFT calculation shows that the charge transfer is from the HOMO of the donor to the SOMO of the three benzyl radical. Compared to PTM, PTM-PSM, PTM-Cz N, PTM-PDCz, the fluorescence quantum efficiency is obviously improved, for example, the luminous efficiency of PTM-Cz N in cyclohexane is up to 0.54, which is 34 times higher than that of PTM's 0.016. This indicates that the connecting electron donor can improve the fluorescence quantum efficiency of the free radical. Meanwhile, we present PTM-PSM, PTM-Cz N, and the PTM-PDCz stability is also huge. This shows that the connecting donor can not only effectively improve the fluorescence quantum efficiency of the free radicals, but also improve the stability of the free radicals. Therefore, the electronic group is a strategy for designing high stability and high fluorescence quantum efficiency. By electrochemical and theoretical calculation, we present the free radical of the group that is connected to the electronic group to show HOMO-S The peculiar property of OMO inversion shows that the HOMO level is above the SOMO level. Because of the space hindrance, the potential of SOMO changes very little, so if HOMO (from the electron group) has high energy, it may be located on the SOMO, and the higher the energy of HOMO, the greater the energy difference between SOMO and HOMO. Therefore, the different donor groups make SOMO The degree of location under HOMO is different. Under HOMO, PTM-PSM is under HOMO, PTM-Cz N is under HOMO-1, PTM-PDCz is under HOMO-3, and the corresponding stability increase corresponds to the SOMO position. The higher the SOMO goes down, the higher the stability is, the higher the.HOMO-SOMO inversion, which makes the electric subdistribution of the free radical molecules violating the principle of structure (Aufbau). A similar result with a partial transition metal, quantum dots, is very rare in organic molecules. By studying the reversal of HOMO-SOMO, it is necessary to increase people's further understanding of the free radicals. At the same time, the fluorescence quantum efficiency of the reverse D-A radical of HOMO-SOMO is greatly improved. Therefore, this is also the design of high fluorescence quantum efficiency, A feasible strategy for highly stable free radicals.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O621.22

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