Syntheses of novel 1,3-diazaazulene derivatives and their nonlinear optical characterization
作者:Yun-Ji Zhu、An-Jun Qin、Li-Min Fu、Xi-Cheng Ai、Zhi-Xin Guo、Jian-Ping Zhang、Cheng Ye
DOI:10.1039/b617810c
日期:——
We have synthesized three new 1,3-diazaazulene derivatives, namely, 2-(4′-N,N-dimethylaminophenyl)-6-nitro-1,3-diazaazulene (18, DMAPNA), 2-(4′-aminophenyl)-6-nitro-1,3-diazaazulene (19, APNA) and 2-[4′-N-(2-hydroxyethyl)aminophenyl]-6-nitro-1,3-diazaazulene (20, HEAPNA), each of them contains an amino substitute as the electron donor (D), 2-phenyl-1,3-diazaazulene as the π-conjugated bridge and a nitro as the electron acceptor (A). Our theoretical results have predicted that these D–π–A type chromophores possess low ground-state dipole moment (μg) and large first-order hyperpolarizability (β), which may facilitate a low degree of aggregation for the chromophores dispersed in a polymeric matrix as well as a large nonlinear optical (NLO) response. The expected NLO performance has been confirmed by the experimental β and μg values, e.g., for 18, 407.8 × 10−30 esu and 4.7 D, respectively. The origins of large β and low μg are explained in terms of a two-state quantum model. The DMAPNA (18)-doped and poled polymethylmethacrylate film exhibits a large second harmonic generation (SHG) coefficient of d33 = 10.9 pm V−1 with excellent thermal stability (above 70% of the maximal SHG coefficient remains at ∼100 °C).
我们合成了三种新的1,3-二氮杂蒽衍生物,分别是2-(4'-N,N-二甲氨基苯基)-6-硝基-1,3-二氮杂蒽(18,DMAPNA)、2-(4'-氨基苯基)-6-硝基-1,3-二氮杂蒽(19,APNA)和2-[4'-N-(2-羟乙基)氨基苯基]-6-硝基-1,3-二氮杂蒽(20,HEAPNA),它们每个都包含作为电子给体(D)的氨基取代基,作为π共轭桥的2-苯基-1,3-二氮杂蒽和作为电子受体(A)的硝基。我们的理论结果预测,这些D–π–A型发色团具有低的基态偶极矩(μg)和大的一级超极化率(β),这可能有助于在聚合物基质中分散的发色团保持低聚集度,以及具有大的非线性光学(NLO)响应。预期的NLO性能已通过实验得到证实,例如,化合物18的β和μg值分别为407.8 × 10^-30 esu和4.7 D。利用两态量子模型解释了大β值和低μg值的起源。掺杂DMAPNA(18)并取向的聚甲基丙烯酸甲酯薄膜表现出大的二次谐波产生(SHG)系数d33 = 10.9 pm V^-1,并且具有优异的热稳定性(在约100°C时维持最大SHG系数的70%以上)。