State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical Chemistry, Jilin University, Changchun, PR China 130012; College of Physics, Jilin University, Changchun 130012, PR China.
State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical Chemistry, Jilin University, Changchun, PR China 130012.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Sep 5;202:70-75. doi: 10.1016/j.saa.2018.05.014. Epub 2018 May 4.
The luminescence and structural changes of 4, 4'-bipyridine in the crystal and powder forms under the effect of high pressure applied by a diamond anvil cell has been investigated through the fluorescence and Raman spectroscopies. In its single crystal structure, the 4, 4'-bipyridine molecules are paralleled arranged with the identifiable CH⋯N and π⋯π interactions among molecules. However, in the powder form, these intermolecular interactions nearly diminish. The 4, 4'-bipyridine crystal shows the obvious bathochromic-shifting of the emission band, which is different from the powder sample that displays a fixed luminescent band during compression. Additionally, the Raman bands of them both show shifts to higher wavenumbers as different degrees. The detailed peak assignments are performed based on the theoretical calculation through B3LYP method. Comparisons in spectral behaviors between the crystal and powder under compression show the crystal form exhibits a superior mechanochromic performance relative to the powder one, because the intermolecular interactions in the crystal form play dominating roles and they can be easily tuned along with pressure in such a highly ordered structure compared to the powder form. The relation investigation between property and supramolecular interactions not only makes deeper understanding in the mechanochromic mechanisms of 4, 4'-bipyridine, but also gives a helpful reference for the molecular designs of coordination polymers and co-crystals with 4, 4'-bipyridine involved.
通过荧光和拉曼光谱研究了在金刚石对顶砧高压作用下，4,4'-联吡啶在晶体和粉末形式下的发光和结构变化。在其单晶结构中，4,4'-联吡啶分子以可识别的 CH⋯N 和分子间π⋯π相互作用平行排列。然而，在粉末形式中，这些分子间相互作用几乎消失。4,4'-联吡啶晶体表现出明显的发射带红移，这与在压缩过程中显示固定发光带的粉末样品不同。此外，它们的拉曼带都表现出不同程度的向高波数移动。根据 B3LYP 方法的理论计算进行了详细的峰分配。在压缩下晶体和粉末之间的光谱行为比较表明，由于晶体形式中的分子间相互作用起主导作用，并且与粉末形式相比，它们可以在这种高度有序的结构中很容易地随压力进行调节，因此晶体形式表现出优于粉末形式的机械变色性能。对性质与超分子相互作用之间关系的研究不仅使我们对 4,4'-联吡啶的机械变色机制有了更深入的了解，而且为涉及 4,4'-联吡啶的配位聚合物和共晶的分子设计提供了有益的参考。
