几个荧光蛋白发色团双光子吸收性质的理论研究（英文）

实验测得的荧光蛋白的单、双光子吸收光谱在低频和高频区域都表现出明显不同的特征。为了揭示这些不同点的起源和研究荧光蛋白的构–效关系,我们详细研究了三种荧光蛋白发色团(一种增强型蓝绿色荧光蛋白的中性发色团和两种红色荧光蛋白的阴离子发色团)的单、双光子吸收特性,分别计算了纯的和振动分辨的电子谱。计算结果表明:光谱线形与计算采用的交换相关密度泛函及谱截面计算所采用的近似关系密切;如果在计算光谱截面时,我们利用长程修正的交换相关泛函CAM-B3LYP来计算几何和电子结构参数,然后把Franck-Condon(FC)效应和包含Herzberg-Teller(HT)效果的电-声耦合效应都考虑进去,理论计算的光谱与实验测定的光谱可以很好地符合;对于两种离子态的发色团,HT电-声耦合效应使得对应于基态到第一激发态跃迁的双光子吸收最强峰相对于单光子吸收的最强峰发生了蓝移,但HT电-声耦合效应对高频的双光子吸收谱没有太大的影响;分子内电荷转移是导致高频区的双光子吸收明显强于单光子吸收的主要原因。     

氢键对绿色荧光蛋白发色团类似物双光子吸收特性的影响（英文）

本文采用分子动力学模拟和量子化学计算相结合的方法,研究了氢键对一种新型供体-受体型绿色荧光蛋白发色团类似物的双光子吸收性质的影响.从分子动力学模拟中提取了氢键复合物的可能构型,并利用二次响应理论方法计算了发色团及其各种氢键复合物的双光子吸收性质,建立了氢键结构与双光子吸收性质之间的关系.结果表明,发色团与溶剂水分子可以通过O…H-O,N-H…O和N…H-O三种类型氢键相结合.O…H-O键的形成导致吸收波长发生红移,双光子吸收截面在一定程度上减小.N-H…O键可以在较长波长处显著增强双光子吸收,而N…H-O键会使吸收波长蓝移,并显著降低双光子吸收截面.应用两态模型,解释了氢键效应产生的原因,并绘制了相关分子轨道,分析了电荷转移特性.此外,通过统计各种氢键复合物的几率,获得了平均双光子吸收谱.本研究为利用氢键网络设计双光子吸收材料提供了良好的理论指导.     

含1,3,5-三嗪和三苯胺的二苯乙烯类双光子材料

合成了以三苯胺为电子给体、1,3,5-三嗪为电子受体的新型二苯乙烯类化合物．用吸收光谱、荧光光谱、飞行质谱、核磁共振氢谱和碳谱进行了表征。这些化合物具有大的双光子吸收截面和强的频率上转换荧光,其中,由三个D-π-A结构的发色团形成的三枝状八偶极分子具有最大的双光子吸收截面和最强的双光子荧光。     

多枝[1,3,4]-噁二唑衍生物的双光子吸收和光功率限幅特性

采用非线性透过率法测定了多枝[1,3,4]-噁二唑衍生物的双光子吸收性质. 测定了化合物的单光子荧光光谱和双光子荧光光谱, 在800 nm波长的激光激发下, 9-乙基-3,6-双{5-(4-叔丁基苯基)-[1,3,4] 噁二唑-2-苯乙烯基}-咔唑(3)和三-{5-(4-叔丁基苯基)-[1,3,4] 噁二唑-2-苯乙烯基-4-苯基}-胺(4)能够发出很强的蓝色和黄绿色双光子上转换荧光, 荧光峰分别位于485和547 nm. 这些多枝结构化合物的双光子吸收截面较大(数值超过104 GM), 并具有很强的光限幅效应. 多枝分子中重复单元的推拉电子结构和协同效应有效地增强了分子的双光子吸收性质.     

1,4-二(4'-N,N-二苯胺基苯乙烯基)苯衍生物单双光子吸收性质的理论研究

随着双光子显微技术的发展,获得性质优良的双光子荧光染料成为研究热点.因此,通过密度泛函理论(DFT)对一系列D-π-A-π-D型1,4-二(4'-N,N-二苯胺基苯乙烯基)苯(DPA-DSB)衍生物平衡几何结构、电子结构、单双光子吸收以及荧光发射性质进行了理论研究,对其结构和光学性质的分析表明,对A,π结构元进行修饰或更换可有效地调节光谱;向分子片段A引入杂原子可有效提高双光子吸收截面;和乙烯基团相比,π桥为乙炔基,若对分子平面性改变不大,则导致分子双光子吸收截面值减小,若乙炔桥很大程度改善分子平面性,则导致分子的TPA截面增大.本研究旨在理解DPA-DSB衍生物分子结构与双光子性质间的关系,为设计合成新型双光子材料提供重要信息.     

二吡唑铝化合物双光子吸收性质的理论研究

应用密度泛函理论(DFT)和半经验的ZINDO方法对二吡唑铝化合物的单、双光子吸收(OPA、TPA)性质进行了研究.结果表明,铝氮烷杂环化合物具有好的双光子吸收性质,其双光子最大吸收截面值(δmax)可达到2860.1 GM(1 GM=10-50 cm4·s·photon-1).在中心、共轭桥和末端引入强的吸电子基团可调谐单、双光子吸收光谱,实现在不同波长范围的双光子吸收;利用三态公式分析了分子的双光子吸收截面变化的内在原因;铝氮烷杂环化合物与其相应的硼化合物相比,表现出类似的单、双光子吸收性质,但一定程度上可增大双光子吸收截面.     

芳基取代咪唑衍生物的合成及其紫外、荧光性质研究

设计合成了两种新颖的三芳基咪唑类化合物5和6,研究了其反应机理,优化了环合加成反应的工艺条件,化合物经FT-IR、HMR和MS进行结构表征。研究了两个化合物在不同溶剂中的紫外与荧光光谱,发现官能苄基的引入,会使吸收峰和发射峰均有不同程度的蓝移,这些光谱性质为今后研究其双光子吸收、双光子荧光和非线性光学性质奠定了实验基础。     

新型卟啉-酞菁二元分子内光物理过程的研究

合成了以哌嗪连接的含卟啉－酞菁的双发色团分子，测定了它的吸收光谱，荧光光谱和荧光寿命。并计算了在不同溶剂中两发色团之间的能量传递效率ΦＥｎＴ和电子转移效率ΦＥＴ。结果表明：在非极性溶剂苯中，两发色团之间的光物理过程以激发态单线态能量传递为主（ΦＥｎＴ８０％）。而在极性溶剂ＤＭＦ中，则以电子转移为主（ΦＥＴ６９．８％）。该二元化合物在ＤＭＦ中，哌嗪以船式构象存在，我们以前合成的以氧或柔性链连接的二元     

红藻条斑紫菜R-藻红蛋白中的能量传递过程

本文通过对条斑紫菜R-PE(藻红蛋白)及其α-β-γ亚基的吸收光谱和荧光光谱进行计算机解叠,研究了R-PE内发色团之间的能量传递过程,并对R-PE及亚基内的各发色团进行了“s”和“f”型的指认。发现在亚基中为“f”型的发色团在R-pE(αβ)₆γ中起着“s”型发色团的作用,且将能量传递给最后的“f”型发色团。荧光激发偏振光谱进一步证明了R-PE内的能量转移过程与计算机解叠的结果一致。     

含三种不同π电子中心的几种双光子吸收材料的理论研究

用密度泛函理论及ZINDO方法,从理论上研究了含二苯乙炔、二苯乙烯和偶氮苯等3种不同π电子中心的几种非线性光学(NLO)材料的双光子吸收截面δ(ω)及三阶非线性光学系数(γ).同时以正确的分子几何构型及UV-Vis光谱为基础,系统地研究和对比了它们的单光子吸收(OPA)和双光子吸收(TPA)的吸收峰位置.     

Differences in two-photon and one-photon absorption profiles induced by vibronic coupling: the case of dioxaborine heterocyclic dye

A theoretical study of a dioxaborine heterocyclic compound in solution provides a case study for an analysis of the effects induced by the so-called Herzberg-Teller (HT) vibronic coupling on the one-(OPA) and two-photon absorption (TPA) spectra. For TPA, the HT vibronic coupling induces differences in the shapes of the absorption band. The study highlights the importance of vibronic coupling as a potentially important mechanism in absorption spectroscopy, able to explain differences in the OPA/TPA spectra.     

2, 5-二氟苯酚分子之旋转异构物的质量分辨阈值电离光谱

利用共振双光子电离(R²PI)技术和质量分辨阈值电离(MATI)技术来研究2, 5-二氟苯酚分子。实验所测得的顺式、反式2, 5-二氟苯酚分子电子激发能E₁分别为36448和36743 cm^-1,绝热电离能分别为71164和71476 cm^-1。这两个顺反转动同素异构分子在电子激发S₁态与离子D₀态活性振动主要是由于面内环变形和与取代基相关的弯曲振动。分析2, 5-二氟苯酚分子的振动光谱、D₀态离子光谱以及理论计算均表明这两个转动异构体在D₀态的几何构型与S₁态的中性几何构型相当相似。     

Two photon absorption of extended substituted phenylenevinylene oligomers: A TDDFT study

Time dependent density functional theory has been applied to analyze the effect of substituent groups on one-photon (OPA) and two-photon (TPA) absorption properties of extended amine-terminated phenylenevinylene oligomers. All investigated molecules are characterized by increased TPA activity. Calculated TPA cross-sections for these compounds do not show TPA enhancements observed in experimental measurements. Stabilization of the TPA active excited state in these chromophores leads to the small (0.2 eV) energy separation between the OPA and TPA allowed excited states, which agrees well with experimental data and may lead to the enhancement of the TPA response due to the strong vibronic couplings.     

Electronic and vibronic contributions to two-photon absorption in donor-acceptor-donor squaraine chromophores

Many squaraines have been observed to exhibit two-photon absorption at transition energies close to those of the lowest energy one-photon electronic transitions. Here, the electronic and vibronic contributions to these low-energy two-photon absorptions are elucidated by performing correlated quantum-chemical calculations on model chromophores that differ in their terminal donor groups (diarylaminothienyl, indolenylidenemethyl, dimethylaminopolyenyl, or 4-(dimethylamino)phenylpolyenyl). For squaraines with diarylaminothienyl and dimethylaminopolyenyl donors and for the longer examples of 4-(dimethylamino)phenylpolyenyl donors, the calculated energies of the lowest two-photon active states approach those of the lowest energy one-photon active (1B(u)) states. This is consistent with the existence of purely electronic channels for low-energy two-photon absorption (TPA) in these types of chromophores. On the other hand, for all squaraines containing indolinylidenemethyl donors, the calculations indicate that there are no low-lying electronic states of appropriate symmetry for TPA. Actually, we find that the lowest energy TPA transitions can be explained through coupling of the one-photon absorption (OPA) active 1B(u) state with b(u) vibrational modes. Through implementation of Herzberg-Teller theory, we are able to identify the vibrational modes responsible for the low-energy TPA peak and to reproduce, at least qualitatively, the experimental TPA spectra of several squaraines of this type.     

Role of donor-acceptor strengths and separation on the two-photon absorption response of cytotoxic dyes: a TD-DFT study

Time-dependent density functional theory (TD-DFT) is applied to model one-photon (OPA) and two-photon (TPA) absorption spectra in a series of conjugated cytotoxic dyes. Good agreement with available experimental data is found for calculated excitation energies and cross sections. Calculations show that both OPA and TPA spectra in the molecules studied are typically dominated by two strong peaks corresponding to different electronic states. We find that donor-acceptor strengths and conjugated bridge length have a strong impact on the cross-section magnitudes of low- and high-frequency TPA maxima, respectively. These trends are analyzed in terms of the natural transition orbitals of the corresponding electronic states. Observed structure-property relationships may have useful implications on design of organic conjugated chromophores with tunable two-photon absorption properties for photodynamic therapy applications.     

Vibronic intensity borrowing. Deuterium effect and emission—absorption asymmetry of the S1---S0 transition in pyrene

The intensities of the vibrationally induced bands in the S₁---S₀ emission and absorption spectra of pyrene-h₁₀ and -d₁₀ are measured and analysed. Several new expressions are reported which relate the deuterium effect and emission—absorption asymmetry of induced spectra to the vibronic coupling mechanism.     

噻吩基卟啉衍生物的单光子和双光子吸收性质的理论研究

本文理论上研究了两个系列的噻吩基卟啉衍生物,这种衍生物在可见光区具有大的双光子吸收截面。用密度泛函理论和ZINDO-SOS方法,计算了分子的几何构型、电子结构,单光子和双光子吸收性质。结果显示噻吩单元的数目影响分子的单光子和双光子吸收性质。具有两个或三个噻吩基团的噻吩基卟啉衍生物在较大范围内具有可用于实际应用中的双光子吸收响应,这一性质有利于这类分子在光限幅中的应用。插入乙炔基有利于扩大共轭范围,增加分子的双光子吸收截面。同时,乙炔基团的加入导致了单光子和双光子波长的红移。从高透明性和相对大的非线性光学响应考虑,噻吩基卟啉衍生物是一类有应用前景的双光子吸收材料。     

2,4-二硫代尿嘧啶的紫外吸收光谱和共振拉曼光谱

硫代嘧啶碱基是光动力疗法潜在的重要光敏剂,其最低单重激发态的光物理研究已有广泛报道。然而,其较高激发态的跃迁性质和反应动力学研究较为稀少。因此,本文采用共振拉曼光谱和密度泛函理论计算方法研究2,4-二硫代尿嘧啶的紫外光谱和几个较高单重激发态的短时结构动力学。首先,基于共振拉曼光谱强度与电子吸收带振子强度f的关系,将紫外光谱去卷积成四个吸收带,分别为358 nm(f=0.0336)中等强度吸收带(A带),338 nm(f=0.1491)、301 nm(f=0.1795)和278 nm(f=0.3532)强而宽的吸收带(B、C和D带)。这一结果既吻合密度泛函理论计算结果,又符合共振拉曼光谱强度模式对紫外光谱带的预期。据此,去卷积得到的四个吸收带被分别指认为S0→S2跃迁、S0→S6跃迁、S0→S7跃迁和S_0→S_8跃迁。同时,分别对B,C和D带共振拉曼光谱进行了详细的指认,获得了短时动力学信息。结果表明,S_8态短时动力学的显著特征是在Franck-Condon区域或附近发生了S8(ππ~*)/S(nπ~*)势能面交叉引发的、伴随超快结构扭转的非绝热过程。S7和S6态短时动力学的主要特征是反应坐标的多维性,它们分别沿C_5C_6/C_2S_8/C_4S_(10)/N_2C_3+C_4N_3H_9/N_1C_2N_3/C_2N_1C_6/C_6N_1H_7/C_5C_6H_(12)和C_5C_6/N_3C_2/C_4S_(10)/C_2S_8+C_6N_1H_7/C_5C_6H_(12)/C_5C_6N_1/C_5C_6H_(12)/C_2N_1C_6/N_1C_2N_3/C_4N_3H_9/N_1C_2N_3等内坐标演化。     

Illuminating the origins of two-photon absorption properties in fluorescent protein chromophores

We provide here a structural impact on two-photon absorption cross-section (σ^TPA) for 22 distinct fluorescent protein (FP) chromophores. By employing time-dependent density functional theory, we gain insight into two-photon absorption (TPA) process by investigating relationship between σ^TPA and one-photon electronic transition dipole moment and permanent dipole moment change (Δμ) upon transition. Our results reveal that for the S₁ excited state, σ^TPA is proportional to (Δμ)² in agreement with two-state model of TPA process. On the contrary, the TPA spectroscopy of higher excited states (S _n, n > 1) is much more complex. We do not find a main driving force of large σ^TPA that would be common for investigated chromophores. Instead, it seems that channel interference between one-photon transition dipole moment vectors is responsible for enhancement or diminishment of σ^TPA. Our in vacuo results may serve as a benchmark to investigate a role of chromophore-protein interaction in shaping TPA spectra of FPs.