X-shaped 1,4-phenyleneethynylenes containing a combination of two main group element moieties of B, Si, or P as part of the side chain have been synthesized. The halogen–lithium exchange of 2-bromo-5-dimethylphenylsilyl-1,4-bis(phenylethynyl)benzene followed by addition of fluorodimesitylborane or chlorodiphenylphosphine gave the “X-shaped” B/Si and Si/P, respectively. The P-containing molecule was oxidized to afford a P(═O) derivative. The B/PO moieties were introduced to the 1,4-phenyleneethynylene unit by 3 steps, i.e., the halogen–lithium exchange of 2,5-dibromo-1,4-bis(trimethylsilylethynyl)benzene followed by sequential addition of fluorodimesitylborane and chlorodiphenylphosphine oxide, desilylation, and the Sonogashira coupling with aryl iodides. Then, the reduction of the B/PO gave “X-shaped” B/P derivative. The absorption and fluorescence spectra of the “X-shaped” molecules showed the molecules have two-dimensional conjugation systems, i.e., the π-conjugation of the original π-conjugation backbone and p(B)π–π* conjugation of B, σ*−π* conjugation of Si, and n−π and σ*−π* conjugation of P, extended from the π-core. The highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy levels are significantly altered because of a lowering of the LUMO level due to p−π* conjugation for B and σ*−π* conjugation for Si and P compared with the parent phenyleneethynylene, which are also supported by density functional theory calculations.

中文翻译：

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侧链上含B，Si或P两个主族元素部分的苯撑乙炔撑的合成及光物理性质

合成了包含B，Si或P的两个主族元素部分的组合作为侧链一部分的X形1，4-亚苯基亚乙炔基。2-溴-5-二甲基苯基甲硅烷基-1,4-双（苯基乙炔基）苯的卤素-锂交换，然后添加氟代二甲基异戊烷或氯代二苯基膦，分别得到“ X形” B / Si和Si / P。含P的分子被氧化以提供P（＝ O）衍生物。通过3个步骤将B / PO部分引入1,4-亚苯基亚乙炔基单元，即2,5-二溴-1,4-双（三甲基甲硅烷基乙炔基）苯的卤素-锂交换，然后依次添加氟代二甲基三茂硼烷和氯代二苯基膦氧化，去甲硅烷基化和Sonogashira与芳基碘化物偶联。然后，B / PO的还原得到“ X形” B / P衍生物。“ X形”分子的吸收和荧光光谱表明，该分子具有二维共轭体系，即原始π共轭骨架的π共轭和B（σ）的p（B）π–π *共轭Si的*-π*共轭，P的n-π和σ*-π*共轭，从π核扩展。由于B的p-π*共轭和Si和P的σ*-π*共轭，导致LUMO能级降低，因此最高占据分子轨道（HOMO）-最低未占据分子轨道（LUMO）能级发生了显着变化。母体亚苯基亚乙炔基，这也得到密度泛函理论计算的支持。Si的σ*-π*共轭，P的n-π和σ*-π*共轭，从π核扩展。由于B的p-π*共轭和Si和P的σ*-π*共轭，导致LUMO能级降低，因此最高占据的分子轨道（HOMO）-最低的未占据分子轨道（LUMO）能级发生了显着变化。母体亚苯基亚乙炔基，这也得到密度泛函理论计算的支持。Si的σ*-π*共轭，P的n-π和σ*-π*共轭，从π核扩展。由于B的p-π*共轭和Si和P的σ*-π*共轭，导致LUMO能级降低，因此最高占据的分子轨道（HOMO）-最低的未占据分子轨道（LUMO）能级发生了显着变化。母体亚苯基亚乙炔基，这也得到密度泛函理论计算的支持。