Geng Kangshuai, Yang Xiaoqian, Zhao Yujie, Cui Yang, Ding Jie, Hou Hongwei
College of Chemistry and Green Catalysis Center, Zhengzhou University, Zhengzhou, Henan 450001, P. R. China.
Inorg Chem. 2022 Aug 8;61(31):12386-12395. doi: 10.1021/acs.inorgchem.2c01785. Epub 2022 Jul 27.
The investigation of third-order nonlinear optical (NLO) properties of coordination polymers (CPs) based on solid samples is very difficult but is crucial for practical applications. Herein, we show a method for preparing high optical quality CP films in a polymer matrix to study the third-order NLO performance of solid-state CPs. Two novel azobenzene-based CPs, [CdL(DMAc)(HO)] () and {[CuL(4,4'-azobpy)]·3HO} () (HL = 5-((4-(phenyldiazenyl)phenoxy)methyl)isophthalic acid), were selected as study subjects. The corresponding microcrystals with a grain size of around 3 μm were doped into poly(vinyl alcohol) (PVA), forming CP films (/PVA and /PVA). /PVA and /PVA exhibit NLO absorption switching behavior from saturable absorption (SA) to reverse saturable absorption (RSA) with increasing pulse energy. Moreover, their NLO properties can also be efficiently modulated by photostimulation energy due to the trans → cis isomerization of an azobenzene moiety. The density functional theory (DFT) results show that the narrower the band gap between the conduction band minimum and the valence band maximum, the denser the electron density distribution in the central mental and coordination atoms, which is beneficial to exhibit better third-order NLO performance. This work provides a feasible method for the wider practical application of solid materials with excellent third-order NLO performance.
基于固体样品研究配位聚合物（CPs）的三阶非线性光学（NLO）性质非常困难，但对于实际应用至关重要。在此，我们展示了一种在聚合物基质中制备高光学质量CP薄膜的方法，以研究固态CPs的三阶NLO性能。选择了两种新型的基于偶氮苯的CPs，[CdL(DMAc)(HO)] () 和 {[CuL(4,4'-azobpy)]·3HO} () （HL = 5-((4-(苯基二氮烯基)苯氧基)甲基)间苯二甲酸）作为研究对象。将相应的粒径约为3μm的微晶掺杂到聚乙烯醇（PVA）中，形成CP薄膜（/PVA和/PVA）。随着脉冲能量增加，/PVA和/PVA呈现出从饱和吸收（SA）到反饱和吸收（RSA）的NLO吸收开关行为。此外，由于偶氮苯部分的反式→顺式异构化，它们的NLO性质也可以通过光刺激能量有效地调节。密度泛函理论（DFT）结果表明，导带最小值和价带最大值之间的带隙越窄，中心金属和配位原子中的电子密度分布越密集，这有利于表现出更好的三阶NLO性能。这项工作为具有优异三阶NLO性能的固体材料的更广泛实际应用提供了一种可行的方法。
