A diphenyl-boron β-diketonate complex was synthesized. Its photophysical properties were studied in solution and in the solid-state, and compared to those of its parent diketone and the corresponding difluoro-boron complex. TD-DFT calculations show that the molecular orbitals involved in the first Franck–Condon transition are very different for the three compounds studied. The difluoro-boron complex is strongly fluorescent in solution, and remains fluorescent in the solid-state. The free diketone turns to be very weakly fluorescent in solution and displays significant Aggregation Induced Enhanced Emission (AIEE) in the crystalline state, which can be explained by a rigidification of the molecule, while the diphenyl-boron complex is weakly fluorescent in solution as well as in the solid-state. For the free diketone and the difluoro-boron complex a mechanofluorochromic response is observed upon grinding the crystalline powder in a mortar, while for the diphenyl-boron complex no fluorescence emission change is detected under these conditions. Overall, this study shows that the nature of the chelating group has a crucial influence on the photophysical and mechanofluorochromic properties of β-diketonate complexes, leading to a wide variety of behaviors within the closely related structures of such derivatives.

中文翻译：

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β-二酮衍生物：螯合基团对光物理和机械氟致变色性质的影响†

合成了二苯基硼β-二酮酸酯络合物。在溶液中和固态下研究了其光物理性质，并与它的母体二酮和相应的二氟硼配合物进行了比较。TD-DFT计算表明，对于所研究的三种化合物，第一次Franck-Condon跃迁所涉及的分子轨道是非常不同的。二氟硼配合物在溶液中呈强荧光，并在固态时保持荧光。游离二酮在溶液中的荧光非常弱，并在结晶状态下显示出显着的聚集诱导的增强发射（AIEE），这可以通过分子的刚性来解释，而二苯硼配合物在溶液中的荧光也很弱。如固态。对于游离的二酮和二氟硼配合物，在研钵中研磨结晶粉末时观察到了机械氟致变色反应，而对于二苯基硼配合物，在这些条件下未检测到荧光发射变化。总体而言，这项研究表明，螯合基团的性质对β-二酮酸酯复合物的光物理和机械荧光致变色性质具有至关重要的影响，从而导致此类衍生物的紧密相关结构中存在多种行为。