Crystalline Arrays of Pairs of Molecular Rotors: Correlated Motion, Rotational Barriers, and Space-Inversion Symmetry Breaking Due to Conformational Mutations
Crystalline Arrays of Pairs of Molecular Rotors: Correlated Motion, Rotational Barriers, and Space-Inversion Symmetry Breaking Due to Conformational Mutations
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DOI：
10.1021/ja4044517
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发表时间：
2013-06-26
影响因子：
15
通讯作者：
Batail, Patrick
中科院分区：
文献类型：
--
作者：
Lemouchi, Cyprien;Iliopoulos, Konstantinos;Batail, Patrick
棒状分子双4-（4-吡啶基）乙炔基）二环[2.2.2]辛-1-基）丁-1，3-二炔，1，含有两个由二炔片段连接的1，4-双（乙炔基）二环[2.2.2]辛（乙炔基）手性旋转体并以一维自组装，单斜C2/c中心对称结构，其中两个平衡位置具有大的占据不平衡（88%对12%）在单个转子现场确定（70-300 K）质子自旋-晶格弛豫，H-1 T-1（-1），在两个不同的H-1拉莫尔频率（55和210 MHz）和DFT计算的旋转障碍，我们能够指定两种类型的布朗旋转具有不同的活化能，1.85和6.1千卡摩尔（-1），的两个H-1自旋晶格弛豫过程的单转子网站。DFT计算的基础上，低能量的过程已被分配给相邻的转子在一个良好的相关同步运动，而高能量的过程是一个突然的变化，在他们的运动学的表现，一旦相邻转子的两个叶片被视为摩擦在一起。虽然1的晶体应该是二次谐波非活性的，但是当电场在平行于独特的转子轴导向器的方向上振荡时，记录了大的二阶光学响应。我们的结论是，通过BCO单元的三个叶片的扭转相互转换的构象突变在与所用光波长相当的纳米尺度上在晶体中的域中打破了处于动态平衡的突变体序列中的空间反转对称性。用类似的四炔分子1的晶体膜进行对照实验，4-双（3-（（三甲基硅基）乙炔基）双环[1.1.1]辛-1-基丁-1，3-二炔，其双环戊烷单元可以旋转，但是非手性的，不产生二阶光学响应。
The rod-like molecule bis 4-(4-pyridyl)ethynyl)bicyclo[2.2.2]oct-1-yl)buta-1,3-diyne, 1, contains two 1,4-bis(ethynyl)bicyclo[2.2.2]octane (ethynyl) chiral rotators linked by a diyne fragment and self assembles in a one-dimensional, monoclinic C2/c centrosymmetric structure where two equilibrium positions with large occupancy imbalance (88% versus 12%) are identified on a single rotor site Combining variable temperature (70-300 K) proton spin-lattice relaxation, H-1 T-1(-1), at two different H-1 Larmor frequencies (55 and 210 MHz) and DFT calculations of rotational barriers, we were able to assign two types of Brownian rotators with different activation energies, 1.85 and 6.1 kcal mol(-1), to the two H-1 spin-lattice relaxation processes on the single rotor site. On the basis of DFT calculations, the low-energy process has been assigned to adjacent rotors in a well-correlated synchronous motion, whereas the high-energy process is the manifestation of an abrupt change in their kinematics once two blades of adjacent rotors are seen to rub together. Although crystals of 1 should be second harmonic inactive, a large second-order optical response is recorded when the electric field oscillates in a direction parallel to the unique rotor axle director. We conclude that conformational mutations by torsional interconversion of the three blades of the BCO units break space-inversion symmetry in sequences of mutamers in dynamic equilibrium in the crystal in domains at a rnesoscopic scale comparable with the wavelength of light used A control experiment was performed with a crystalline film of a similar tetrayne molecule, 1,4-bis(3-((trimethylsilyl)ethynyl)bicyclo-[1.1.1]pent-1-yObuta-1,3-diyne, whose bic-ydopentane units can rotate but are achiral and produce no second-order optical response.