Cationic NLO-chromophores based on tolane Ï-systems in which conventional electron donors are combined with ionic pyridinio or triorganoammonio and -phosphonio substituents, respectively, perform much better than conventional donor/acceptor-substituted (D/A-substituted) tolanes concerning their hyperpolarisabilityâtransparency trade-off. This effect occurs because ionic acceptors do not enlarge the Ï-system in contrast to conventional acceptors. The same holds true for benzene-type chromophores. Despite their different electronic nature, the extrapolated maximal high-energy absorption of the ionic chromophore series as well as of the conventional donor/acceptor-tolanes coincide at the absorption energy of unsubstituted tolane. This proves that the maximal blue transparency of a given series of substituted chromophores is governed by the absorption maximum of the unsubstituted parent chromophore. In this way chromophores have been designed with much higher quadratic hyperpolarisability than e.g.p-nitroaniline at about the same absorption wavelength. By applying the same concept, a two- and a three-dimensional highly efficient octupolar NLO-chromophore assembly has also been synthesised.
基于
甲烷-系统的阳离子非线性光学发色团,其中传统的电子供体分别与离子
吡啶基或三有机胺基和
磷烷基取代基结合,在超极化性和透明度之间的权衡方面,其性能远远优于传统的供体/受体取代(D/A取代)
甲烷。这种效应的发生是因为离子受体不会像传统受体那样扩大-系统。苯基发色团也是如此。尽管它们的电子性质不同,但离子发色团系列以及传统的供体/受体-
甲烷的最大高能量吸收与未取代
甲烷的吸收能量相吻合。这证明,特定取代发色团系列的最大蓝色透明度是由未取代母体发色团的吸收最大值决定的。通过这种方式,发色团被设计为具有比对
硝基苯胺更高的二次超极化率,而吸收波长大致相同。通过应用相同的概念,还合成了一种二维和三维的高效八极子非线性光学发色团组装。