Carter Ash G, Saha Promeet K, Sikder Antara, Aguilar Juan A, Monkman Andrew P, Avestro Alyssa-Jennifer, Etherington Marc K, McGonigal Paul R
Department of Chemistry, University of York, Heslington, YO10 5DD, UK.
Department of Chemistry, Durham University, Durham, DH1 3LE, UK.
Angew Chem Int Ed Engl. 2025 Aug 18;64(34):e202505433. doi: 10.1002/anie.202505433. Epub 2025 Jun 25.
Emissive organic salts have long been integral to the discovery of fluorescence phenomena and functional luminescent dyes. Typically, one component of the salt acts as the photoactive unit (luminophore) and its nonemissive counterion is selected to independently tune bulk physical properties, such as solubility. However, the impact of counterion choice on the aggregation and resulting emissive state of organic salts in solution has not been widely investigated. Here, we report that a single cationic luminophore gives rise to either monomer, dimer, excimer, or multichromatic emission under otherwise identical conditions by varying only its counterion. We employ N-methyl quininium (MeQn) as a permanently charged cationic luminophore, which we pair with a series of monovalent anions. At low solution-state concentrations, all the salts give identical absorption and emission spectra that correlate with the MeQn monomer. However, at higher concentrations, the emission, excitation, and absorption data differ, revealing the presence of monomer, dimer, excimer, or all three, depending on the structure of the anion. Understanding and modulating the formation of dimeric or other well-defined aggregated species by specific ion effects could be exploited in the design of molecular probes for biological systems or emissive thin-film dispersions for optoelectronic devices.
发光有机盐长期以来一直是荧光现象和功能性发光染料发现的重要组成部分。通常，盐的一种成分充当光活性单元（发光体），其非发光抗衡离子被选择用于独立调节整体物理性质，如溶解度。然而，抗衡离子的选择对溶液中有机盐的聚集及由此产生的发光状态的影响尚未得到广泛研究。在此，我们报告，在其他条件相同的情况下，仅通过改变其抗衡离子，单一阳离子发光体就能产生单体、二聚体、准分子或多色发射。我们使用N-甲基喹宁鎓（MeQn）作为带永久电荷的阳离子发光体，并将其与一系列单价阴离子配对。在低溶液态浓度下，所有盐都给出与MeQn单体相关的相同吸收和发射光谱。然而，在较高浓度下，发射、激发和吸收数据不同，这表明根据阴离子的结构存在单体、二聚体、准分子或三者皆有。通过特定离子效应理解和调节二聚体或其他明确聚集物种的形成，可用于设计生物系统的分子探针或光电器件的发光薄膜分散体。
