A new mechanoluminescent material (4-(diphenylamino)phenyl)(4-(diphenylphosphanyl)phenyl)methanone (CDpP), which displays tunable mechanoluminescent emission colors, has been designed and successfully synthesized. CDpP shows two distinct mechanoluminescent colors (blue and green) in different crystalline states. Single-crystal analyses and femtosecond transient emission studies reveal that the striking tunable mechanoluminescence properties of CDpP mainly originate from the different C–H⋯π interactions in the crystal structures. CDpP crystals with more C–H⋯π interactions show blue mechanoluminescence (ML), and the emission is attributed to the locally excited (LE)-state because the twisting process for the excited state is restricted by C–H⋯π interactions. Conversely, CDpP crystals with fewer C–H⋯π interactions display green ML, in which the red-shifted emission band originates from the twisted intramolecular charge transfer (TICT) excited state because the diphenylamine moiety is relatively free to rotate. The manipulation of weak intermolecular interactions in the crystalline state is a useful and reliable strategy for the tuning of the ML emission wavelengths.

中文翻译：

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相互作用弱，但作用强：可通过调节分子间C–H⋯π相互作用来调节机械发光†

已设计并成功合成了一种新型的机械发光材料（4-（二苯基氨基）苯基）（4-（二苯基膦酰基）苯基）甲酮（CDpP），该材料显示出可调节的机械发光发射色。CDpP在不同的晶态下显示两种不同的机械发光颜色（蓝色和绿色）。单晶分析和飞秒瞬态发射研究表明，CDpP惊人的可调机械发光特性主要源自晶体结构中不同的C–H⋯π相互作用。具有更多C–H⋯π相互作用的CDpP晶体显示出蓝色机械发光（ML），并且发射归因于局部激发（LE）状态，因为激发态的扭曲过程受到C–H⋯π相互作用的限制。相反，具有较少C–H⋯π相互作用的CDpP晶体显示绿色ML，其中红移发射带源自扭曲的分子内电荷转移（TICT）激发态，因为二苯胺部分相对自由旋转。晶态中弱分子间相互作用的操纵是用于调整ML发射波长的有用且可靠的策略。