Electron-deficient π-conjugated functional dyes lie at the heart of organic optoelectronics. Adding nitro groups to aromatic compounds usually quenches their fluorescence via inter-system crossing (ISC) or internal conversion (IC). While strong electronic coupling of the nitro groups with the dyes ensures the benefits from these electron-withdrawing substituents, it also leads to fluorescence quenching. Here, we demonstrate how such electronic coupling affects the photophysics of acceptor–donor–acceptor fluorescent dyes, with nitrophenyl acceptors and a pyrrolo[3,2-b]pyrrole donor. The position of the nitro groups and the donor-acceptor distance strongly affect the fluorescence properties of the bis-nitrotetraphenylpyrrolopyrroles. Concurrently, increasing solvent polarity quenches the emission that recovers upon solidifying the media. Intramolecular charge transfer (CT) and molecular dynamics, therefore, govern the fluorescence of these nitro-aromatics. While balanced donor-acceptor coupling ensures fast radiative deactivation and slow ISC essential for large fluorescence quantum yields, vibronic borrowing accounts for medium dependent IC via back CT. These mechanistic paradigms set important design principles for molecular photonics and electronics.

缺电子 π 共轭功能染料是有机光电子学的核心。向芳香族化合物中添加硝基通常会通过系统间交叉 (ISC) 或内部转换 (IC) 来淬灭它们的荧光。虽然硝基与染料的强电子耦合确保了这些吸电子取代基的好处，但它也会导致荧光猝灭。在这里，我们展示了这种电子耦合如何影响受体-供体-受体荧光染料的光物理特性，包括硝基苯基受体和吡咯并 [3,2- b ] 吡咯供体。硝基的位置和供体-受体距离强烈影响双分子的荧光性质-硝基四苯基吡咯并吡咯。同时，增加溶剂极性会抑制在固化介质时恢复的发射。因此，分子内电荷转移 (CT) 和分子动力学控制着这些硝基芳烃的荧光。虽然平衡的供体-受体耦合确保了快速的辐射失活和缓慢的 ISC 对于大的荧光量子产率至关重要，但电子振动借用通过背面 CT 解释了介质依赖性 IC。这些机械范例为分子光子学和电子学设定了重要的设计原则。