Yang Yue-Ju, Li Shi-Xiong, Chen De-Liang, Long Zheng-Wen
School of Physics and Electronic Science, Guizhou Education University, Guiyang 550018, China.
College of Physics, Guizhou University, Guiyang 550025, China.
ACS Omega. 2022 Nov 1;7(45):41266-41274. doi: 10.1021/acsomega.2c04941. eCollection 2022 Nov 15.
Here, the ground-state structures, electronic structures, polarizability, and spectral properties of metal-free phthalocyanine (HPc) under different external electric fields (EEFs) are investigated. The results show that EEF has an ultrastrong regulation effect on various aspects of HPc; the geometric structures, electronic properties, polarizability, and spectral properties are strongly sensitive to the EEF. In particular, an EEF of 0.025 a.u. is an important control point: an EEF of 0.025 a.u. will bend the benzene ring subunits to the positive and negative directions of the planar molecule. Flipping the EEF from positive (0.025 a.u.) to negative (-0.025 a.u.) flips also the bending direction of benzene ring subunits. The HPc shows different dipole moments projecting an opposite direction along the direction (-84 and 84 Debye for EEFs of -0.025 and 0.025 a.u., respectively) under negative and positive EEF, revealing a significant dipole moment transformation. Furthermore, when the EEF is removed, the molecule can be restored to the planar structure. The transformation of the HPc structure can be induced by the EEF, which has potential applications in the molecular devices such as molecular switches or molecular forceps. EEF lowers total energy and reduces highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap; especially, an EEF of 0.025 a.u. can reduce the HOMO-LUMO gap from 2.1 eV (in the absence of EEF) to 0.37 eV, and thus, it can enhance the molecular conductivity. The first hyperpolarizability of HPc is 0 in the absence of EEF; remarkably, an EEF of 0.025 a.u. can enhance the first hyperpolarizability up to 15,578 a.u. Therefore, HPc under the EEF could be introduced as a promising innovative nonlinear optical (NLO) nanomaterial such as NLO switches. The strong EEF (0.025 a.u.) causes a large number of new absorption peaks in IR and Raman spectra and causes the redshift of electronic absorption spectra. The changes of EEF can be used to regulate the structure transformation and properties of HPc, which can promote the application of HPc in nanometer fields such as molecular devices.
在此，研究了不同外部电场（EEF）下无金属酞菁（HPc）的基态结构、电子结构、极化率和光谱性质。结果表明，EEF对HPc的各个方面具有超强的调控作用；几何结构、电子性质、极化率和光谱性质对EEF高度敏感。特别地，0.025原子单位的EEF是一个重要的控制点：0.025原子单位的EEF会使苯环亚基向平面分子的正负方向弯曲。将EEF从正（0.025原子单位）翻转到负（-0.025原子单位）也会使苯环亚基的弯曲方向翻转。在负EEF和正EEF下，HPc沿方向显示出不同的偶极矩，方向相反（EEF为-0.025和0.025原子单位时分别为-84和84德拜），揭示了显著的偶极矩转变。此外，当去除EEF时，分子可恢复到平面结构。EEF可诱导HPc结构的转变，这在分子开关或分子镊子等分子器件中具有潜在应用。EEF降低了总能量并减小了最高占据分子轨道-最低未占据分子轨道（HOMO-LUMO）能隙；特别是，0.025原子单位的EEF可将HOMO-LUMO能隙从2.1电子伏特（无EEF时）降低到0.37电子伏特，因此，它可增强分子导电性。在无EEF时，HPc的第一超极化率为0；值得注意的是，0.025原子单位的EEF可将第一超极化率提高到15578原子单位。因此，EEF作用下的HPc可作为一种有前景的创新非线性光学（NLO）纳米材料，如NLO开关。强EEF（0.025原子单位）在红外和拉曼光谱中产生大量新的吸收峰，并导致电子吸收光谱的红移。EEF的变化可用于调控HPc的结构转变和性质，这可促进HPc在分子器件等纳米领域的应用。
