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几类有机双光子吸收材料的理论研究
Theoretical Investigation on Several Organic Two-photon Absorption Materials
【作者】 赵杨；
【导师】 任爱民；
【作者基本信息】 吉林大学 ， 物理化学， 2010， 博士
【摘要】 双光子吸收是非线性光学现象的一种,是指一个原子或分子同时吸收两个光子向高能级跃迁的过程。在过去的几十年里双光子吸收材料在化学、物理等科学领域都有很重要的应用,近些年来它在生命科学领域的应用也越来越受到人们的关注。因此从理论上设计研究具有优良双光子吸收性质的材料是这一科学领域的重要基础。本论文主要对几类有机双光子吸收材料进行了系统的理论研究。首先用密度泛函方法(DFT)进行分子的几何构型优化,然后在优化得到的平衡几何构型基础上采用半经验的ZINDO方法、完全态求和公式(SOS)及我们自己编制的FTRNLO程序计算得到了与分子的单光子和双光子吸收性质相关的信息。并进一步揭示了分子结构与单、双光子吸收性质的内在联系,为理论设计和实验合成具有优良双光子吸收性质的材料提供了有价值的理论依据。本论文主要内容如下:1.研究了一系列四羧酸二萘嵌苯衍生物分子,揭示了四羧酸二萘嵌苯是一种分子刚性很好的主体结构,加强分子末端取代基的给电子能力或扩大分子长轴方向上共轭长度都可以有效的改良此类衍生物分子的双光子吸收性质。2.研究了一系列芘衍生物分子,揭示了向芘分子主体引入取代基数目、位置的变化和形成环状共轭二聚体对其双光子吸收性质的影响,并阐明了双光子吸收过程中振子强度变化与双光子吸收截面大小的内在联系。3.研究了一系列星型DCM衍生物分子,揭示了溶剂效应对分子几何结构和单、双光子吸收性质的影响及溶剂介电常数与分子内电荷转移情况、双光子吸收截面之间的内在联系。4.设计研究了一系列以苯并[h]苯并呋喃为基础的二价镁离子双光子荧光探针分子。揭示了增强此类探针分子对镁离子的双光子荧光响应的有效途径及其本质原因。为生物活体内的镁离子探测提供了重要的理论依据。
【Abstract】 Novel two-photon absorption (TPA) materials have attracted increasing interest in recent years due to their potential applications in many different fields such as chemistry, physics and biology. Up to now, the practical TPA materials are still limited, further exploring and researching on new materials with potential TPA properties are urgent. In this thesis, several organic TPA materials have been systematic theoretical investigated. The density functional theory has been used to optimize the geometrical structure. On the basis of the equilibrium geometries, the one- and two-photon absorption properties have been calculated by ZINDO program combine SOS equation and self-compiled FTRNLO program. Then, the internal relations between molecular structure and one- and two-photon absorption properties have been revealed. These investigations will provide some useful and valuable information for designing and synthesizing novel TPA materials with large TPA cross-section values.1. The investigation on the perylene tetracarboxylic derivatives (PTCDs) reveal that increasing the number of naphthalene nucleus, extending the conjugated length on long axis, increasing the strength of donor group on lateral side, and keeping the conjugation effect and inductive effect along the same molecular axis are the efficient ways to enlarge TPA cross-section of PTCDs.The formula of predicting the maximum TPA cross-section of PTCDs compounds are obtained by the relationship between the maximum TPA cross-section and the number of naphthalene nucleus on long axis or number of biphenyl on short axis. PTCDs exibit extremly large TPA cross-section and they are promising TPA materials. 2. A series of pyrene derivatives have been theoretically studied. Results show that pyrene derivatives exhibit extremely large TPA cross-sections and present strong OPA around 400 nm, which indicate that introducing donor groups to pyrene molecule, increasing the number of donor groups, extending the conjugated length, or forming circular conjugated dimmer are all efficient ways to enlarge TPA cross-sections. All these results give us some basic principles to design pyrene derivatives with large TPA cross-sections. This shed light into the significance of the pyrene derivatives as promising fluorescent probes in biochemistry when it was linked to some special recognizing groups.3. The solvent effect on DCM derivatives have been studied. Results show that increasing the number of branches in DCM molecules and introducing stronger electron withdrawing groups are efficient ways to enhance the TPA cross-sections. Investigations on the solvent effects reveal that TPA cross-section increases as the polarity of the solvents increases and it reaches the maximum when the dielectric constantεequal to 20.7. ICT show regular changes which are in agreement with the changing trend of the TPA cross sections, and the products of transition dipole moments andΔQ are all linearly proportional to the TPA cross-sections.4. A series of magnesium ion (Mg2+) selective fluorescent probes based on benzo[h]chromene derivatives have been theoretically studied. Results show that all the studied probe molecules exhibit large TPA cross-sections in response to Mg2+ in 700-1200 nm range. The TPA cross-sections can be greatly enhanced by introducing acceptor groups to the lateral side of benzo[h]chromene, and that probes with stronger acceptor group show larger TPA cross-sections and result in 70-fold enhancing when coordinate with Mg2+. These results shed light into the design strategy of efficient TP fluorescent probes with large TPA cross-sections for Mg2+ sensing in living systems.