A coplanar donor-acceptor (D-A) structure in single crystal is directly observed for TICT-Type DPA-PYZ, which corresponds to a coplanar localized excited (LE) state. The conversion between coplanar LE and twisted intramolecular charge transfer (TICT) excited state in the solid state can be achieved through the change of the D-A twist angle between ~0° and ~30° during grinding, heating and solvent fumigation processes. This twist angle change between donor and acceptor was proved by the Raman, FT-IR spectroscopy and X-ray crystallographic analysis as well as theoretical calculation. This research provides the clear evidence for the conversion between coplanar LE and TICT excited states of D-A molecules in solid state and contributes much to the deep understanding of stimulus-response behavior of fluorescent D-A molecular solids from the viewpoint of excited state control.

对于TICT型DPA-PYZ，可以直接观察到单晶中的共面供体-受体（DA）结构，它对应于共面局部激发（LE）状态。在研磨，加热和溶剂熏蒸过程中，DA扭曲角在〜0°和〜30°之间变化，可以实现固态的共面LE和扭曲的分子内电荷转移（TICT）激发态之间的转换。供体和受体之间的这种扭转角变化已通过拉曼光谱，FT-IR光谱和X射线晶体学分析以及理论计算得到了证明。