双环金属铱(Ⅲ)异腈配合物的二阶非线性光学性质

采用密度泛函理论(DFT)方法对双环金属Ir(III)异腈配合物的非线性光学(NLO)性质进行计算研究。用B3PW91(UB3PW91)(金属原子采用LANL2DZ基组，非金属原子采用6-31G*基组)方法对配合物进行几何结构优化。在优化构型基础上，采用B3PW91(UB3PW91)和B3LYP(UB3LYP)方法计算了配合物的第一超极化率(βtot)，并用CAM-B3LYP(UCAM-B3LYP)(金属原子采用LANL2DZ基组，非金属原子采用6-31G**基组)方法模拟配合物的吸收光谱。结果表明，主配体的取代基(R1)和副配体的取代基(R2)对第一超极化率值贡献不大。配合物发生氧化还原反应，电荷转移方式增多，电荷转移程度增大，使βtot值显著增加，其中1a+((C∧N)2Ir(CNR)2]+(R=CH3))发生氧化反应和还原反应的βtot值分别增大了75倍和144倍。因此，这类双环金属铱(III)异腈配合物的氧化还原反应可以有效地调节其二阶NLO性质。

Second-Order Nonlinear Optical Properties of Bis-Cyclometalated Iridium(III) Isocyanide Complexes

The second-order nonlinear optical (NLO) properties of bis-cyclometalated iridium(Ⅲ) isocyanide complexes were investigated by density functional theory (DFT). In this work, the geometries of the complexes were optimized using the B3PW91(UB3PW91) functional and they were found to be in good agreement with experimental data. The 6-31G^* basis set was used for the non-metal elements while the LANL2DZ basis set was used for iridium. From the optimized geometries the total first hyperpolarizabilities (β_tot) of the complexes were calculated by the B3PW91(UB3PW91) and B3LYP(UB3LYP) functionals. Because the polarization and diffuse function may have a nontrivial effect on the calculation of the first hyperpolarizabiliy the more flexible and polarized 6-31+G^* non-metal atom basis sets and the LANL2DZ basis set for iridium were used. The absorption spectra of all the complexes were calculated at the CAM-B3LYP(UCAM-B3LYP)/6-31+G^** (LANL2DZ iridium atom) level in acetonitrile to obtain a deeper insight into the second-order NLO properties of these complexes. The results indicate that the second-order NLO response is not strongly affected by different substituents, while the redox reaction plays an important role in improving the second-order NLO response and this comes from a change in the charge transfer pattern and an increase in the degree of charge transfer. The β_tot values of the one-electron oxidized/reduced species (1a²⁺/1a)(complexes cyclometalated with N-arylazolesand alkyl isocyanides, (C^∧N)₂Ir(CNR)₂]⁺ (R=CH₃)) are 75 and 144 times larger than that of the eigenstate complex (1a⁺), respectively. Therefore, the redox reaction of the cationic bis-cyclometalated iridium isocyanide complexes can effectively tune the second-order NLO properties.