The influence of pentafluorophenyl groups on the nonlinear optical (NLO) performance of high generation dendrons and dendrimers

Abstract

With the aim to make the influence of pentafluorophenyl groups in the periphery of high generation dendrons and dendrimers on their NLO performance clearly, some NLO dendrons and dendrimers with different chromophore moieties or different end-capped groups were carefully designed and investigated in detail. The results demonstrated that some strong Ar-ArF interactions between the pentafluorophenyl groups in the periphery and the normal phenyl rings of the donors, could influence the topological structures of dendrons or dendrimers, and then affect their NLO performance. Furthermore, the optical transparency and the stability of the dendrons and dendrimers with pentafluorophenyl groups as end-capped moieties were all improved, in comparison with normal dendrons and dendrimers containing phenyl ones as the end-capped groups.

Ar–ArF Self‐Assembly of Star‐Shaped Second‐Order Nonlinear Optical Chromophores Achieving Large Macroscopic Nonlinearities

“…Encouragingly, two new signals appeared at the 19 F NMR spectrum of T3 , although both intensities are very weak. However, their chemical shifts, locating at ≈140 and ≈151 ppm, respectively, are very consistent with those found in our previous work . We therefore think these two newly weak signals observed at the 19 F NMR spectrum of T3 , to a large degree, could be due to the Ar–Ar F self‐assembly effect, but not derived from the noise or technical error.…”

“…As well demonstrated in our previous work, [25][26][27] when introducing pentafluorobenzene groups in the periphery of high generation dendrimers, new signals can be observed in addition to the original three signals at the 19 F NMR spectra due to the strong Ar-Ar F self-assembly effect. To check whether this assembly effect can be induced by the multibranched structure, we also conducted the 19 F NMR spectra of T1-T3 as shown in Figure 2.…”

“…However, their chemical shifts, locating at ≈140 and ≈151 ppm, respectively, are very consistent with those found in our previous work. [25][26][27] We therefore think these two newly weak signals observed at the 19 F NMR spectrum of T3, to a large degree, could be due to the Ar-Ar F self-assembly effect, but not derived from the noise or technical error. By further comparing with the results of T1 and T2, the Ar-Ar F selfassembly for T3 may be also explained by the change of topological structure, meaning the increase of chromophore arms makes the topological structure more spherical, as evidenced by the geometry simulation results shown in Figure S6 (Supporting Information).…”

“…In addition to optimizing the topological structure of dendrimers, another efficient design approach to achieve high NLO performance is the use of controlled aromatic/perfluoroaromatic (Ar–Ar F ) self‐assembly to enhance the poling efficiency . Our group has carried out a systematical study of the impact of pentafluorophenyl groups in the periphery of dendrimers on their NLO performance, and the results indicated that the induced Ar–Ar F self‐assembly effect in dendrimers mainly came from the intramolecular interactions between the pentafluorophenyl rings in the periphery and the electron donor parts in the interior, unlike those are based on intermolecular interactions reported by Jen and co‐workers . Moreover, such assembly effect can become more and more obvious upon increasing generation of dendrimers, therefore improving the NLO performance more efficiently.…”

“…The macroscopic NLO activities of T1-T3 were measured using similar methods as reported, [25][26][27] and their d 33 values are calculated at the 1064 nm fundamental wavelength from the experimental data as summarized in Table 2. It should be pointed out that all the multibranched chromophores exhibit very good solubility, and can be easily handled to prepare thin films on indium tin oxide (ITO) glass substrates through The maximum absorption wavelengths in diluted THF solutions (2.5 × 10 −5 mol mL −1 ); b) The 5% weight loss temperature detected by the thermogravimetric (TG) analyses under nitrogen at a heating rate of 10 °C min; c) The best poling temperature; d) The film thickness; e) Second harmonic generation coefficient;…”