Thulaseedharan Nair Sailaja Sidharth, Maisuls Iván, Kösters Jutta, Hepp Alexander, Faust Andreas, Voskuhl Jens, Strassert Cristian A
Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 28/30, 48149 Münster, Germany.
CeNTech, CiMIC, SoN, Westfälische Wilhelms-Universität Münster, Heisenbergstraße 11, 48149 Münster, Germany.
Beilstein J Org Chem. 2020 Dec 2;16:2960-2970. doi: 10.3762/bjoc.16.246. eCollection 2020.
In this work, a series of γ-substituted diphenylnaphthalonitriles were synthesized and characterized. They show efficient emission in solution and in the aggregated state and their environment responsiveness is based on having variable substituents at the -position of the two phenyl moieties. The excited state properties were fully investigated in tetrahydrofuran (THF) solutions and in THF/HO mixtures. The size of the aggregates in aqueous media were measured by dynamic light scattering (DLS). The steady-state and time-resolved photoluminescence spectroscopy studies revealed that all the molecules show intense fluorescence both in solution and in the aggregated state. In THF solutions, a blue emission was observed for the unsubstituted (H), methyl- (Me) and -butyl- (-Bu) substituted γ-diphenylnaphthalonitriles, which can be attributed to a weak π-donor capability of these groups. On the other hand, the methoxy- (OMe), methylsulfanyl- (SMe) and dimethylamino- (NMe) substituted compounds exhibit a progressive red-shift in emission compared to H, Me and -Bu due to a growing π-electron donating capability. Interestingly, upon aggregation in water-containing media, H, Me and -Bu show a slight red-shift of the emission and a blue-shift is observed for OMe, SMe and NMe. The crystal structure of Me allowed a detailed discussion of the structure-property relationship. Clearly, N-containing substituents such as NMe possess more electron-donating ability than the S-based moieties such as SMe. Moreover, it was found that NMe showed higher luminescence quantum yields (Φ) in comparison to SMe, indicating that N-substituted groups could enhance the fluorescence intensity. Therefore, the π-donor nature of the substituents on the phenyl ring constitutes the main parameter that influences the photophysical properties, such as excited state lifetimes and photoluminescence quantum yields. Hence, a series of highly luminescent materials from deep blue to red emission depending on substitution and environment is reported with potential applications in sensing, bioimaging and optoelectronics.
在本工作中，合成并表征了一系列γ-取代的二苯基萘腈。它们在溶液和聚集态下均表现出高效发射，且其环境响应性基于两个苯基部分的γ-位具有可变取代基。在四氢呋喃（THF）溶液和THF/水混合物中对激发态性质进行了全面研究。通过动态光散射（DLS）测量了水性介质中聚集体的尺寸。稳态和时间分辨光致发光光谱研究表明，所有分子在溶液和聚集态下均表现出强烈的荧光。在THF溶液中，未取代（H）、甲基-（Me）和丁基-（-Bu）取代的γ-二苯基萘腈观察到蓝色发射，这可归因于这些基团较弱的π-供体能力。另一方面，甲氧基-（OMe）、甲硫基-（SMe）和二甲氨基-（NMe）取代的化合物与H、Me和-Bu相比，发射出现逐渐红移，这是由于π-电子供体能力增强。有趣的是，在含水性介质中聚集时，H、Me和-Bu发射出现轻微红移，而OMe、SMe和NMe观察到蓝移。Me的晶体结构允许对结构-性质关系进行详细讨论。显然，含氮取代基如NMe比基于硫的部分如SMe具有更强的供电子能力。此外，发现NMe与SMe相比表现出更高的发光量子产率（Φ），表明N-取代基团可增强荧光强度。因此，苯环上取代基的π-供体性质构成影响光物理性质如激发态寿命和光致发光量子产率的主要参数。因此，报道了一系列根据取代和环境从深蓝色到红色发射的高发光材料，在传感、生物成像和光电子学方面具有潜在应用。
