Figueira João, Rodrigues João, Russo Luca, Rissanen Kari
Centro de Química da Madeira, LQCMM/MMRG, Departamento de Química da Universidade da Madeira, 9000-390 Funchal, Portugal.
Acta Crystallogr C. 2008 Feb;64(Pt 2):o33-6. doi: 10.1107/S0108270107065523. Epub 2008 Jan 12.
2,5-Diethoxy-1,4-bis[(trimethylsilyl)ethynyl]benzene, C(20)H(30)O(2)Si(2), (I), constitutes one of the first structurally characterized examples of a family of compounds, viz. the 2,5-dialkoxy-1,4-bis[(trimethylsilyl)ethynyl]benzene derivatives, used in the preparation of oligo(phenyleneethynylene)s via Pd/Cu-catalysed cross-coupling. 2,5-Diethoxy-1,4-diethynylbenzene, C(14)H(14)O(2), (II), results from protodesilylation of (I). 1,4-Diethynyl-2,5-bis(heptyloxy)benzene, C(24)H(34)O(2), (III), is a long alkyloxy chain analogue of (II). The molecules of compounds (I)-(III) are located on sites with crystallographic inversion symmetry. The large substituents either in the alkynyl group or in the benzene ring have a marked effect on the packing and intermolecular interactions of adjacent molecules. All the compounds exhibit weak intermolecular interactions that are only slightly shorter than the sum of the van der Waals radii of the interacting atoms. Compound (I) displays C-H...pi interactions between the methylene H atoms and the acetylenic C atom. Compound (II) shows pi-pi interactions between the acetylenic C atoms, complemented by C-H...pi interactions between the methyl H atoms and the acetylenic C atoms. Unlike (I) or (II), compound (III) has weak nonclassical hydrogen-bond-type interactions between the acetylenic H atoms and the ether O atoms.
2,5 - 二乙氧基 - 1,4 - 双[（三甲基硅基）乙炔基]苯，C₂₀H₃₀O₂Si₂，（I），是一类化合物中最早在结构上得到表征的实例之一，即2,5 - 二烷氧基 - 1,4 - 双[（三甲基硅基）乙炔基]苯衍生物，用于通过钯/铜催化的交叉偶联制备聚（亚苯基乙炔）。2,5 - 二乙氧基 - 1,4 - 二乙炔基苯，C₁₄H₁₄O₂，（II），由（I）的去硅烷基化反应生成。1,4 - 二乙炔基 - 2,5 - 双（庚氧基）苯，C₂₄H₃₄O₂，（III），是（II）的长烷氧基链类似物。化合物（I） - （III）的分子位于具有晶体学反演对称性的位点上。炔基或苯环中的大取代基对相邻分子的堆积和分子间相互作用有显著影响。所有化合物都表现出弱的分子间相互作用，其距离仅略短于相互作用原子的范德华半径之和。化合物（I）在亚甲基H原子和炔基C原子之间表现出C - H...π相互作用。化合物（II）在炔基C原子之间表现出π - π相互作用，并由甲基H原子和炔基C原子之间的C - H...π相互作用补充。与（I）或（II）不同，化合物（III）在炔基H原子和醚O原子之间具有弱的非经典氢键型相互作用。
