Petrov Nikolai Kh, Ivanov Denis A, Alfimov Michael V
Photochemistry Center RAS, FSRC "Crystallography and Photonics" RAS, ul. Novatorov 7A, 119421 Moscow, Russia.
Moscow Institute of Physics and Technology (State University), Institutsky per. 9, 141707 Dolgoprudny, Russia.
ACS Omega. 2019 Jul 2;4(7):11500-11507. doi: 10.1021/acsomega.9b01158. eCollection 2019 Jul 31.
The relaxation mechanism of electronically excited states of host-guest complexes between cucurbiturils (CB) and pyridinium styryl dyes is considered in detail on the basis of the recent results obtained by the up-conversion fluorescence technique. The addition of CB to aqueous dye solutions increases the longest fluorescence decay times from about 50 ps for the free dyes to 100-150 ps for the bound ones. This is attributed to the braking of intramolecular rotations around the single bonds of the styryl moiety that is provided by guest's displacement inside the cavity, whose driving force is a Coulombic interaction of the styryl dye cation and negatively charged CB portals. This displacement, a translational movement along the CB axis, is associated with the observed decay time of about 1 ps. There is also a characteristic time of about 100 fs, attributed to vibrational relaxation. In fact, such complexes can operate as a molecular machine, the molecular switch.
基于上转换荧光技术最近获得的结果，详细研究了葫芦脲（CB）与吡啶鎓苯乙烯基染料之间主客体配合物电子激发态的弛豫机制。向染料水溶液中添加CB会使最长荧光衰减时间从游离染料的约50 ps增加到结合染料的100 - 150 ps。这归因于苯乙烯基部分单键周围分子内旋转的制动，这是由客体在腔内的位移提供的，其驱动力是苯乙烯基染料阳离子与带负电荷的CB端口之间的库仑相互作用。这种位移，即沿CB轴的平移运动，与观察到的约1 ps的衰减时间相关。还有一个约100 fs的特征时间，归因于振动弛豫。实际上，这种配合物可以作为分子机器，即分子开关发挥作用。
