Effective expansion of the subporphyrin chromophore through conjugation with meso-oligo(1,4-phenyleneethynylene) substituents:: Octupolar effect on two-photon absorption
Effective expansion of the subporphyrin chromophore through conjugation with meso-oligo(1,4-phenyleneethynylene) substituents:: Octupolar effect on two-photon absorption
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DOI：
10.1002/anie.200801192
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Osuka, Atsuhiro
中科院分区：
文献类型：
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作者：
Inokuma, Yasuhide;Easwaramoorthi, Shanmugam;Osuka, Atsuhiro
亚卟啉是一种具有碗状结构的环收缩的卟啉，由于其强烈的吸收和14P-共轭芳环产生的明亮的绿色荧光，已成为一种有前途的功能颜料。[1-3]与自1972年Meller和Ossko首次报道以来广泛研究的亚酞菁3的化学相比，亚卟啉1和2的化学仍处于起步阶段。[5]在卟啉化学中，4中的中位芳基取代基是控制金属卟啉反应的功能单元共价键的关键合成手柄，用于向中心金属中心提供空间位阻，从而保护金属卟啉不受分子间干扰等。[6]因此，在大多数情况下，中位芳基取代基的作用仅限于通过提供相对于卟啉平面具有明确定义的几何构型的位置来进行功能制备。换句话说，中位芳基取代基对卟啉p-体系的电子影响很小，这主要是由于它们限制了与卟啉平面的垂直排列。这一边际影响与卟啉氧化还原电位Hammett图上较小的1值是一致的(在E_1/2，红色或E_1/2图中，1=0.073和0.065 V，OX对4 S)。[7]相反，我们最近发现，亚卟啉的1值很大(0.124和0.105 V)，[1b]，这表明中位芳基取代基的电子影响很大。这一有趣的性质得益于介孔芳基取代基的自由旋转和HOMO和LUMO中介观位置的大轨道系数。在这里，我们报道了5，10，15-三低聚(1，4-苯乙叉)取代的亚卟啉10-13(见方案1)的合成和非线性光学(NLO)性质，其中亚卟啉的p电子体系在包括低聚(1，4-苯乙叉)[8]臂的整个分子中有效地离域。方案1概述了10-13的合成路线。4-溴苯基取代亚卟啉5与三甲基硅基乙炔(6)、苯乙炔(7)和4-苯乙炔(8)进行Sonogashira偶联反应，分别以96%、96%和95%的产率得到10-12。值得注意的是，亚卟啉10-12很容易溶于CH2Cl2、CHCl3和甲苯，尽管存在三个没有任何大体积取代基的低聚(1，4-苯乙叉)单元。13的产率仅为58%，这可能是由于乙炔前体9的溶解性较差所致。亚卟啉10-13具有类似的1H核磁共振谱，其特征是外围b质子在d=8.12-8.17ppm范围内有一个单重态，对于1，4-亚苯乙炔基团，在2，6-或3，5-位没有区分两个亚苯质子。这些1H核磁共振数据表明亚卟啉10-13的C3对称性和中位芳基取代基的自由旋光。
Subporphyrin, a ring-contracted porphyrin with a bowlshaped structure, has emerged as a promising functional pigment because of its intense absorption and bright green fluorescence which arise from its 14p-conjugated aromatic circuit.[1–3] The chemistry of subporphyrins 1 and 2 has remained in its infancy, compared to the chemistry of subphthalocyanines 3 that has been extensively studied [4] since the first report by Meller and Ossko in 1972.[5] In porphyrin chemistry, the meso-aryl substituents in 4 have served as key synthetic handles for the covalent linkage of functional units, the anchoring of chelating units for controlling the reactivity of metalloporphyrins, for providing steric hindrance to the central metal center thus protecting metalloporphyrins from intermolecular interference, and so forth.[6] As such, the roles of meso-aryl substituents are in most cases limited to being structural through providing sites for functional fabrications with well-defined geometries with respect to the porphyrin plane. In other words, the electronic impact of meso-aryl substituents on the porphyrin p-system is only marginal, this is due mainly to their restricted perpendicular arrangements to the porphyrin plane. This marginal influence is consistent with small 1 values for Hammett plots of the redox potentials of porphyrins (1= 0.073 and 0.065 V in the plot of E1/2, red or E1/2, ox vs. 4 s).[7] In contrast, we have recently revealed that the 1 values are large (0.124 and 0.105 V) for subporphyrins,[1b] which indicates a large electronic influence of the meso-aryl substituents. This interesting property is aided by the free rotation of the meso-aryl substituents and the large orbital coefficients at the meso-position in the HOMO and LUMO. Herein, we report the synthesis and nonlinear optical (NLO) properties of 5, 10, 15-tris-oligo (1, 4-phenyleneethynylene) substituted subporphyrins 10–13 (see Scheme 1), in which the p-electron system of the subporphyrins is effectively delocalized over the whole molecule including the oligo (1, 4-phenyleneethynylene)[8] arms. Scheme 1 outlines the synthetic routes to 10–13. Sonogashira coupling reactions of 4-bromophenyl-substituted subporphyrin 5 with trimethylsilylacetylene (6), phenylacetylene (7), and 4-(phenylethynyl) phenylacetylene (8) proceeded quantitatively to give 10–12 in 96, 96, and 95%, yields respectively. It is worth noting that subporphyrins 10–12 are readily soluble in CH2Cl2, CHCl3, and toluene despite the presence of three oligo (1, 4-phenyleneethynylene) units without any bulky substituents. The yield of 13 was only 58%, probably because of the poor solubility of the acetylene precursor 9. Subporphyrins 10–13 exhibit similar 1H NMR spectral patterns, featuring a singlet in the range of d= 8.12–8.17 ppm for the peripheral b-protons and a single set of signals without discrimination of the two phenylene protons at the 2, 6-or 3, 5-positions for the 1, 4-phenyleneethynylene groups. These 1H NMR data indicate the C3-symmetry for the subporphyrins 10–13 and free rotation of the meso-aryl substituents.