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Similarities and differences between Mn(II) and Zn(II) coordination polymers supported by porphyrin-based ligands: synthesis, structures and nonlinear optical properties.
Dalton Transactions ( IF 3.5 ) Pub Date : 2020-08-24 , DOI: 10.1039/d0dt02450c
Bo-Wei Xu 1 , Ru-Jie Niu 1 , Quan Liu 2 , Jun-Yi Yang 3 , Wen-Hua Zhang 1 , David J Young 4
Affiliation  

Four coordination polymers (CPs) Mn-TMPP (1), Zn-TMPP (2), Mn-THPP (3), and Zn-THPP (4) have been synthesized and characterized (H2TMPP = meso-tetrakis (6-methylpyridin-3-yl) porphyrin; H2THPP = meso-tetrakis (6-(hydroxymethyl) pyridin-3-yl) porphyrin). The one-dimensional (1D) chain compound 1 is formed via a head-to-tail connection of the Mn-TMPP unit, wherein the central Mn2+ features a square pyramidal geometry coordinated by four N atoms from the porphyrin skeleton and one additional N atom from an adjacent Mn-TMPP unit. Compound 2 features an octahedral Zn2+ center associated with four N atoms from the porphyrin skeleton to define the equatorial plane and two additional N donors at the axial positions to give a two-dimensional (2D) CP. The 1D chain of 1 and the 2D layer of 2 possess distinctive molecular structures but nearly identical molecular arrangements in their unit cells viewed along all three crystallographic axes. By contrast, Mn- and Zn-based CPs 3 and 4 supported by the THPP ligand share both identical molecular connectivities and crystal packing. In 3/4, each Mn/Zn center is chelated by four N donors of the porphyrin interior to define the equatorial plane of an octahedron, whose axial sites are occupied by two alcoholic OH groups from a pair of trans-located pyridinemethanol moieties. The third-order nonlinear optical properties of 1–4 investigated using the Z-scan technique at 532 nm revealed reverse saturable absorption and self-focusing effects for all four CPs, with hyperpolarizability values (γ) in the range 1.42 × 10−28 esu to 7.64 × 10−28 esu. These high γ values are comparable to the best porphyrin-based molecular assemblies, demonstrating potential for these materials in optical limiting applications.

中文翻译:

卟啉基配体支持的Mn(II)和Zn(II)配位聚合物之间的异同:合成,结构和非线性光学性质。

合成并表征了四种配位聚合物(CP)Mn-TMPP(1),Zn-TMPP(2),Mn-THPP(3)和Zn-THPP(4)(H 2 TMPP = meso -tetrakis(6-甲基吡啶-3-基卟啉; H 2 THPP =内消旋四(6-(羟甲基)吡啶-3-基)卟啉。一维(1D)链状化合物1通过Mn-TMPP单元的头尾连接形成的,其中中心Mn 2+具有正方形的金字塔形几何结构,该结构由来自卟啉骨架的四个N原子和一个附加的来自相邻的Mn-TMPP单元的N原子。化合物2其特征是一个八面体Zn 2+中心,该中心与来自卟啉骨架的四个N原子相关联以定义赤道平面,并在轴向位置处具有两个附加的N供体以提供二维(2D)CP。从所有三个晶体学轴上看,1的1D链和2的2D层具有独特的分子结构,但它们的晶胞中的分子排列几乎相同。相比之下,由THPP配体支撑的基于Mn和Zn的CP 34具有相同的分子连接性和晶体堆积。在3 / 4,每个Mn / Zn中心被卟啉内部的四个N供体螯合,以定义八面体的赤道面,其八面体的轴向位点被一对位的吡啶甲醇部分中的两个醇羟基占据。使用Z扫描技术在532 nm处研究的1-4的三阶非线性光学性质显示了所有四个CP的反向饱和吸收和自聚焦效应,超极化率值(γ)在1.42×10 -28 esu范围内至7.64×10 -28 esu。这些高γ 该值可与基于卟啉的最佳分子组装相媲美,证明了这些材料在光学限制应用中的潜力。
更新日期:2020-09-22
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