系列苯炔化合物和苯炔树枝大分子的合成及其光学性质的研究

合成了一系列苯炔化合物, 并对它们的紫外吸收和荧光发射性质进行了研究. 通过HOMO和LUMO轨道能量差ΔE、分子轨道图及相关碳原子上的电荷密度讨论了分子结构和大小对这些化合物紫外吸收和荧光发光性质的影响. 在间位苯炔化合物及间位苯炔树枝大分子(dendrimer)中, 紫外吸收峰不随苯炔分枝数和dendrimer阶数增加而红移, 共轭被中心苯环隔断. 而在邻或对位取代的苯炔化合物中, 共轭则不受中心苯环的影响而延伸至整个分子. 其原因可能和中心苯环上与苯炔分枝相连的碳原子的电荷密度有关. 在激发态下, 间位苯炔化合物中苯炔分枝间存在耦合作用, 荧光发射随苯炔分枝数增加而红移. 但这种耦合作用只发生在与同一苯环相连的分枝间, 因此荧光发射不随dendrimer阶数增加而红移.

Synthesis and Optical Property Studies of Phenylacetylene and Its meta-Connected Dendrimers

A series of phenylacetylenes and the meta-connected dendrimers were synthesized. Their UV absorption and fluorescence emission properties were discussed through the energy gap AE between HOMO and LUMO orbitals, the orbital diagrams and the charge densities of the related carbon atoms. The reason that the conjugation in the meta-connected phenylacetylenes and the meta-connected dendrimers is interrupted by the central benzene ring, but can be extended to the whole molecule in the para- and orthoconnected phenylacetylenes, possibly related to the charge density of the carbon atom to be located at the central benzene ring to connect the phenylethynyl branch. In the excited state, there is a coupling effect between the phenylethynyl branches connecting the same benzene ring. Therefore, the fluorescence emissions were red-shifted with increasing the number of phenylethynyl branches connecting the central benzene ring in the meta-connected phenylacetylenes, but not red-shifted with increasing the generation of the dendrimer.