平面型卟啉类衍生物吸收光谱的密度泛函计算  

DFT Calculation of Absorption Spectra for Planar Porphyrin Derivatives

作　　者：周彩华[1] 丁晓 ZHOU Cai-hua;DING Xiao(College of Chemistry and Chemical Engineering,Xianyang Normal University,Xianyang 712000,China)

机构地区：[1]咸阳师范学院化学与化工学院,陕西咸阳712000

出　　处：《光谱学与光谱分析》2022年第6期1769-1773,共5页Spectroscopy and Spectral Analysis

基　　金：陕西省自然科学基础研究计划项目(2021JQ-820);陕西省教育厅项目(18JK0836)资助。

摘　　要：用于光动力疗法(PDT)中的光敏剂是一类吸收一定波长的光后达到激发三重态,然后将三重态能量转移给生物体内的氧分子使得基态氧激发为单线态氧的一类物质。目前,临床应用的光敏剂大部分是以卟啉为主的平面型分子。平面分子一般具有较大的共轭键,被光激发后系间窜跃小,三重态寿命较长,因此可以获得高产率的单线态氧。然而临床使用的这类光敏剂吸收波长位于紫外区域,照射光会对人体组织造成光损伤,因此改善临床光敏剂光毒性特征,合成具有可见光区域吸收波段的光敏剂是光动力疗法研究的重要内容之一。该研究依据密度泛函(DFT)及其含时理论(TD-DFT),对三类平面型卟啉衍生物[耳坠型卟啉(a),三磺酸基酞菁(b),三磺酸基酞菁合Ni(Ⅱ)(c)]的基态和激发态性质进行了严格的密度泛函计算。几何优化计算显示:分子(a)的最稳定构型中,所有原子都处于一个平面,分子直径大约是7,分子空穴达到5。分子(b)所有的原子也处于同一平面,分子直径达到8,但是分子空穴只有4。分子(c)的最稳定构型与平面结构发生了偏离,这是由于金属Ni的四配位倾向形成变形四面体,分子的空穴变得更小。几何优化结果说明耳坠型卟啉分子大的空穴有助于其捕获更多的基态氧并进行能量传递。前线轨道能量和轨道布局计算显示:耳坠型分子(a)最高占据能量是最高的,即电子更易被激发。三类分子的最高占据轨道与最低空轨道的能级间隔分别为0.072,0.076和0.075 a.u.,可以看出耳坠型分子(a)有最低的能级间隙。从轨道布局来看,三类分子中所有原子的p轨道参与了共轭大π键的形成,其中分子(c)中金属d轨道也参与了大π键的形成。对三类分子的吸收光谱进行了模拟,三类分子都具有卟啉特有的Soret带和Q带。(a)分子Q带位于450~900 nm,(b)分子和(c)分子的Q带位于400~800 nm,其中(a)分子的最大吸收�The photosensitizer was applied photodynamic therapy(PDT), a molecule that can absorb light with a certain wavelength. And the photosensitizer can transfer excited energy to ground state oxygen. As a result, the ground state oxygen gets the energy and becomes the singlet oxygen. Currently, those applied photosensitizers are almost planar molecules containing porphyrin ring, and those planar molecules have a big delocalized π bonds. Simultaneously, there is a slight inter-system crossing and a long triplet lifetime after the planar molecules are excited by light. So those planar molecules have a high yield of singlet oxygen. However, the absorption bands of the applied photosensitizers always lie in the UV regions, which easily damage the body issue. Due to the photo-damage character is not beneficial for the therapy, so the study on photosensitizers with Vis-IR absorption bands were widely concerned. Based on the above reason, we investigate three photosensitizers(earing-porphyrin(a), trisulfo-phthalocyanine(b) and trisulfo-phthalocyanine Ni(Ⅱ)(c)) using the DFT and TD-DFT. The optimized results show that all atoms of(a) are in a plane, the radius of(a) is almost 7A, and the cavity radius is 5A. All atoms of(b) are also in a plane, the radius of trisulfo-phthalocyanine is 8A, and the radius of the cavity is 4A. But(c) is a distorted plane due to the coordinated mode of Ni(Ⅱ). Therefore, the earing-porphyrin(a) in a big cave can capture more ground-state oxygen. The orbital energies and populations show that the HOMO energy of(a) is the biggest among them. That is, the electrons of the earing-porphyrin(a) were excited to higher energy levels easily. The energy gaps(E_(homo-lumo)) of three molecules are 0.072, 0.076 and 0.075 a.u. The earing-porphyrin(a) has the lowest energy gap. The orbital populations show that the atomic p orbitals constitute the big delocalized bond, and the d orbitals of Ni also join in the delocalized bond in the molecule(c). At last, the absorption spectra of three molecules were simul

关 键 词：光敏剂 卟啉 密度泛函 吸收光谱 

分 类 号：O641[理学—物理化学]