Fonseca Ruben D, Vivas Marcelo G, Silva Daniel Luiz, Eucat Gwenaelle, Bretonnière Yann, Andraud Chantal, Mendonca Cleber R, De Boni Leonardo
Instituto de Física de São Carlos , Universidade de São Paulo , 13560-970 São Carlos , SP , Brazil.
Departamento de Fisica , Universidad popular del Cesar , Barrio Sabana , 2000004 Valledupar , Cesar , Colombia.
J Phys Chem Lett. 2019 May 2;10(9):2214-2219. doi: 10.1021/acs.jpclett.9b00518. Epub 2019 Apr 22.
The intramolecular cooperative effect in branched molecules is a consequence of the interaction and extent of electronic coupling among the different axes of charge transfer. Such an effect is the key to obtain remarkable nonlinear optical response in molecular systems. Here we show that triphenylamine derivative molecules containing only two branches present the strongest electronic interaction between them at the excited state, generating exponential enhancement of the 2PA cross section. The primary factor for such behavior was ascribed to the substantial extent and interaction of the π-electron delocalization promoted by the strong electron-donating and acceptor antisymmetrical groups present in each branch. However, for the three-branch molecules we observed an anticooperative effect, i.e., the 2PA cross section decreases as compared to the one-branch structure as we normalized the signal by the effective π-electron number in each molecule.
支化分子中的分子内协同效应是电荷转移不同轴之间相互作用及电子耦合程度的结果。这种效应是在分子体系中获得显著非线性光学响应的关键。在此我们表明，仅含两个支链的三苯胺衍生物分子在激发态时它们之间呈现出最强的电子相互作用，导致双光子吸收（2PA）截面呈指数增强。这种行为的主要因素归因于每个支链中强给电子和受体不对称基团所促进的π电子离域的显著程度和相互作用。然而，对于三支链分子，我们观察到了反协同效应，即当我们通过每个分子中的有效π电子数对信号进行归一化时，与单支链结构相比，2PA截面减小。
