共查询到18条相似文献,搜索用时 93 毫秒
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用AMl+INDO/SDCI方法对3-羟基吡啶酰胺的激发态质子转移反应进行了理论研究,求得基态和激发态反应位能面、势垒和过渡态.对有关化合物的吸收和荧光光谱进行了理论指认,所有理论计算结果均与实验结果吻合较好.在此基础上对光化学反应机理和应用前景进行了讨论. 相似文献
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3-羟基对氧萘酮分子内激发态质子转移反应位能面和机理的研究 总被引:1,自引:0,他引:1
封继康 《高等学校化学学报》1989,10(11):1114-1118
用MNDO和INDO-SCF-CI法研究了3-羟基对氧萘酮分子内激发态质子转移反应基态和激发态的位能面,求得相应能垒△E1、△E2和荧光移位,并对光化学反应机理进行了探讨. 相似文献
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9—羟基苯并萘酮的结构和激发态质子转移过程 总被引:1,自引:0,他引:1
用INDO系列方法对9-羟基苯并萘酮的结构和激发态质子转移过程进行了理论研究,求得基态和激发态反应的位能面、势垒和过渡态,对反应机理进行了探讨。 相似文献
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采用ab initio HF理论的组态相关CIS方法和连续溶剂模型PCM, 分别在6-311+G*和6-31G水平上研究了6-甲基-4-羟基嘧啶单体及二聚体激发态质子转移的异构化反应; 对其反应势能面的研究发现, 单体基态和激发态的异构化反应一起可以形成四能级的分子电子体系, 而二聚体的却不能, 由此解释了单体和二聚体的紫外吸收光谱和荧光发射光谱均对应于酮式构型的原因. 利用混合含时密度泛函TD/MPW1PW91理论方法在溶剂存在下计算了标题物质的紫外吸收光谱和荧光发射光谱. 相似文献
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使用量子化学中的Hartree-Fock方法和密度泛函理论中的B3LYP方法,分别在3-21G^*和6-31G(d)水平上,计算了尿酸分子从三羰基异构体向三羟基异构体的转化。结果表明,转化过程经历了单羟基和双羟基异构体2种中间物和3种过渡态时的分子内质子转移(IPT),转移中的H原邻近的N,O和C原子形成了具有四元环结构的过渡态。随着IPT的进行,N-H键逐渐被削弱和断裂,O-H键则逐渐生成。3个反应的活化能分别为190.3kJ/mol,181.4kJ/mol和249.9kJ/mol(B3LYP/6-31G(d))。较高的活化能表明在室温下,无催化剂的IPT难以进行。 相似文献
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Effect of Solvent Polarity on Excited-State Double Proton Transfer Process of 1, 5-Dihydroxyanthraquinone 下载免费PDF全文
Zheng-Ran Wang Li-Xia Zhu Xing-Lei Zhang Bo Li Yu-Liang Liu Yong-Feng Wan Qi Li Yu Wan Hang Yin Ying Shi 《化学物理学报(中文版)》2022,35(2):289-294
The excited-state double proton transfer (ESDPT) properties of 1, 5-dihydroxyanthraquinone (1, 5-DHAQ) in various solvents were investigated using femtosecond transient absorption spectroscopy and the DFT/TDDFT method. The steady-state fluorescence spectra in toluene, tetrahydrofuran (THF) and acetonitrile (ACN) solvents presented that the solvent polarity has an effect on the position of the ESDPT fluorescence emission peak for the 1, 5-DHAQ system. Transient absorption spectra show that the increasing polarity of the solvent accelerates the rate of excited state dynamics. Calculated potential energy curves analysis further verified the experimental results. The ESDPT barrier decreases gradually with the increase of solvent polarity from toluene, THF to ACN solvent. It is convinced that the increase of solvent polarity can promote the occurrence of the ESDPT dynamic processes for the 1, 5-DHAQ system. This work clarifies the mechanism of the influence of solvent polarity on the ESDPT process of 1, 5-DHAQ, which provides novel ideas for design and synthesis of new hydroxyanthraquinone derivatives. 相似文献
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Excited-state double proton transfer (ESDPT) has been studied in a variety of 1-azacarbazole (1AC) hosted hydrogen-bonded complexes. In 1 AC/carboxylic acids hydrogen bonded complexes, large association constants of > 1.0 × 104 M?1 are measured in the ground state and the rate of ESDPT is » 5.0 × 109 s?1, resulting in a dominant proton-transfer tautomer emission. In several 1 AC/lactam hydrogen bonded complexes, however, spectral and dynamic results show the existence of a fast excited-state equilibrium between normal and proton-transfer tautomer states. The result can be tentatively rationalized by a non-catalytic ESDPT mechanism incorporating tautomerization energy of the guest molecule. 相似文献
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Regulation of Excited-State Intramolecular Proton Transfer Process and Photophysical Properties for Benzoxazole Isothiocyanate Fluorescent Dyes by Changing Atomic Electronegativity 下载免费PDF全文
Excited-state intramolecular proton transfer (ESIPT) is favored by researchers because of its unique optical properties. However, there are relatively few systematic studies on the effects of changing the electronegativity of atoms on the ESIPT process and photophysical properties. Therefore, we selected a series of benzoxazole isothiocyanate fluorescent dyes (2-HOB, 2-HSB, and 2-HSeB) by theoretical methods, and systematically studied the ESIPT process and photophysical properties by changing the electronegativity of chalcogen atoms. The calculated bond angle, bond length, energy gap, and infrared spectrum analysis show that the order of the strength of intramolecular hydrogen bonding of the three molecules is 2-HOB < 2-HSB < 2-HSeB. Correspondingly, the magnitude of the energy barrier of the potential energy curve is 2-HOB > 2-HSB > 2-HSeB. In addition, the calculated electronic spectrum shows that as the atomic electronegativity decreases, the emission spectrum has a redshift. Therefore, this work will offer certain theoretical guidance for the synthesis and application of new dyes based on ESIPT properties. 相似文献
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Excited-State Double Proton Transfer of 1, 8-Dihydroxy-2-Naphthaldehyde: a MS-CASPT2//CASSCF Study 下载免费PDF全文
Excited-state double proton transfer (ESDPT) is a controversial issue which has long been plagued with theoretical and experimental communities. Herein, we took 1, 8-dihydroxy-2-naphthaldehyde (DHNA) as a prototype and used combined complete active space self-consistent field (CASSCF) and multi-state complete active-space second-order perturbation (MS-CASPT2) methods to investigate ESDPT and excited-state deactivation pathways of DHNA. Three different tautomer minima of S1-ENOL, S1-KETO-1, and S1-KETO-2 and two crucial conical intersections of S1S0-KETO-1 and S1S0-KETO-2 in and between the S0 and S1 states were obtained. S1-KETO-1 and S1-KETO-2 should take responsibility for experimentally observing dual-emission bands. In addition, two-dimensional potential energy surfaces (2D-PESs) and linear interpolated internal coordinate paths connecting relevant structures were calculated at the MS-CASPT2//CASSCF level and confirmed a stepwise ESDPT mechanism. Specifically, the first proton transfer from S1-ENOL to S1-KETO-1 is barrierless, whereas the second one from S1-KETO-1 to S1-KETO-2 demands a barrier of ca. 6.0 kcal/mol. The linear interpolated internal coordinate path connecting S1-KETO-1 (S1-KETO-2) and S1S0-KETO-1 (S1S0-KETO-2) is uphill with a barrier of ca. 12.0 kcal/mol, which will trap DHNA in the S1 state while therefore enabling dual-emission bands. On the other hand, the S1/S0 conical intersections would also prompt the S1 system to decay to the S0 state, which could be to certain extent suppressed by locking the rotation of the C5$-$C8$-$C9$-$O10 dihedral angle. These mechanistic insights are not only helpful for understanding ESDPT but also useful for designing novel molecular materials with excellent photoluminescent performances. 相似文献
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The equilibrium constants, K
2, have been determined for the proton-transfer reactions of 1-phenacylquinolinium ion, PHQ+, with several amines {triethylamine (TEA), N,N,N′,N′-tetramethylethylenediamine (ED), N,N,N′, N′-tetramethylpropanediamine (PD), N,N,N′,N′-tetramethylbutanediamine (BD), and 1,8-bis(dimethylamino-naphthalene (DMAN)} in acetonitrile (AN), AN-tetrahydrofuran (THF)
and AN-ethanol (EtOH) mixtures. The reaction was followed spectrophotometrically using a stopped-flow technique. The K
2 value decreased for DMAN and increased for TEA with increasing vol-% of THF in AN-THF mixtures. The changes in the K
2 value for ED, PD and BD changed in the order: ED, PD and BD from a pattern similar to TEA to a pattern similar to DMAN. The
change in the K
2 value for DMAN with increasing vol-% of THF in AN-THF mixtures was explained by the effect of polarity on the stability of
P−Q+ (the deprotonated product of PHQ+). The effect of THF on the K
2 value is consistent with that of the peak wavelength of the absorption spectrum of P−Q+. The change in the K
2 value for TEA, ED, PD and BD depended on the structures of the protonated bases, one of the products for this reaction. The
effect of EtOH on the K
2 value for DMAN was examined in ternary EtOH-THF-AN mixtures that contain different amounts of EtOH and whose relative permittivities
were adjusted to that of EtOH. The K
2 value increased with increasing vol-% of EtOH because of the stabilization of P−Q+ upon the formation of the hydrogen-bonded complex with EtOH. The absorption spectrum of P−Q+ demonstrated a blue shift as the vol-% of EtOH increased. 相似文献
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In this short review, we attempt to unfold various aspects of excited-state intramolecular proton transfer (ESIPT) from the studies that are available up to date. Since Weller’s discovery of ESIPT in salicylic acid (SA) and its derivative methyl salicylate (MS), numerous studies have emerged on the topic and it has become an attractive field of research because of its manifold applications. Here, we discuss some critical aspects of ESIPT and tautomerization from the mechanistic viewpoint. We address excitation wavelength dependence, anti-Kasha ESIPT, fast and slow ESIPT, reversibility and irreversibility of ESIPT, hydrogen bonding and geometrical factors, excited-state double proton transfer (ESDPT), concerted and stepwise ESDPT. 相似文献
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The excited state intramolecular proton transfer (ESIPT) processes in 3‐methylsalicyclic acid (3‐MeSA) and 3‐methoxysalicyclic acid (3‐MeOSA) have been investigated in cyclohexane medium by emission spectroscopic techniques. The ESIPT process was characterized in 3‐MeSA from the large Stokes fluorescent band (455 nm), but it was suppressed by 3‐MeOSA in cyclohexane. The ESIPT process was found to be accelerated both in 3‐MeSA and 3‐MeOSA in the presence of a hydrogen bond accepting agent, triethylamine (TEA). Further, theoretical calculations were carried out at the ground and excited states to complement the experimental evidences. 相似文献
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Perylenequinoidsarephotosensitive.BecausetheycaneffectivelykilltumorcellsandinhibitHIVviruses,peoplehavepaidmuchattentiontotheminrecentyearsandexpectedthemtobecomeanewkindofmedicinefortreatmentoftumorandAIDSI.ThereasonwhyitispossibletousePerylenequinoidsasmedicineisthattheypossessexcellentphotosensitivepropertiessuchasgoodthermalstability,highlevelof'O,quantumyield,andeastnessofpurification,etc2-4.Theseperformancesaredeterminedbytheiruniquemolecularstructure(Figurel).Theymayhaveintramolec… 相似文献