State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun, 130023, People's Republic of China.
Dalton Trans. 2012 Oct 28;41(40):12416-27. doi: 10.1039/c2dt31252b.
The systematic investigation of the linear and nonlinear optical properties on such a class of hexa-peri-hexabenzocoronene (HBC) chromophores is of significance for rationally designing two-photon absorption (TPA) materials. The results indicate that increasing the strength of electron-donating or accepting terminal groups leads to bathochromic-shift of the absorption band and enhancement of the TPA cross section (δ(max)). For the molecules with fluorinated methylene and cyano substituents, replacement of a double bond by a triple bond in the conjugated linker produces the increase of δ(max), owing to the lower bond-length alternation and better rigidity of phenylene-ethynylene. In contrast, for the molecules with nitro groups, the similar replacement results in a slight decrease of δ(max) because N-HBC-E-NO2 has excellent planarity architecture and effective electronic coupling. The TPA spectra are red-shifted and the δ(max) values are enhanced as the number of branches increases. Thus, a solvatochromism effect has a positive influence on the TPA response of the nitryl compounds due to larger polarization of the nitro moiety. We have shed light on the linear relationship between the first hyperpolarizability and δ(max). These HBC derivatives hold potential as high-performance nonlinear optical materials.
系统研究了这一类六并苯并六元杂环（HBC）发色团的线性和非线性光学性质，对于合理设计双光子吸收（TPA）材料具有重要意义。结果表明，增加供电子或吸电子端基的强度会导致吸收带的红移和 TPA 截面（δ(max)）的增强。对于具有氟化亚甲基和氰基取代基的分子，在共轭连接体中用三键取代双键会导致 δ(max)的增加，这是由于苯乙炔的键长交替和更好的刚性降低。相比之下，对于具有硝基取代基的分子，由于 N-HBC-E-NO2 具有优异的平面结构和有效的电子耦合，类似的取代会导致 δ(max)略有下降。TPA 光谱红移，随着支化度的增加，δ(max)值增强。因此，由于硝基部分的更大极化，溶剂化效应对硝化物的 TPA 响应有积极影响。我们已经阐明了第一超极化率和 δ(max)之间的线性关系。这些 HBC 衍生物有望成为高性能非线性光学材料。
