Lee Sae Hui, Valverde Paredes Marco S, Forster Paul M, Lee Dong-Chan
Department of Chemistry and Biochemistry, University of Nevada Las Vegas 4505 S. Maryland Parkway, Box454003 Las Vegas Nevada 89154-4003 USA
RSC Adv. 2024 Feb 19;14(9):6285-6291. doi: 10.1039/d4ra00816b. eCollection 2024 Feb 14.
In this work, we report alkoxy substituted benzil based all organic room temperature phosphors which showed crystallization induced phosphorescence (CIP). Nine title compounds were prepared with various alkyl lengths (OCH: = 8-16) and the effect of alkyl side group length on the phosphorescence performance was investigated, as compared to -anisil. It was found that both phosphorescence quantum yield and lifetime increased concomitantly as the alkyl length increased up to nonyloxy (BZL-OC9). Further increase in the carbon number caused the phosphorescence performance to deteriorate due to greater conformational freedom of the side groups. An incredible quantum yield of 70% was achieved for BZL-OC9. A promising finding is that the increased quantum yield was accompanied by the increase in the lifetime relative to -anisil, which has been historically challenging. Single crystallography coupled with UV-Vis spectroscopy revealed that a higher level of intermolecular π-π interactions was observed from -anisil while more alkyl interactions with less intermolecular π-orbital overlap were found for BZL-OC8. As a result, molecular rigidification with less phosphorescence quenching was achieved for BZL-OC8 leading to enhanced performance. A precipitation study on a dichloromethane solution as a function of the content of MeOH (poor solvent) proved that the emission of the BZL-OC system is truly aggregation-induced. The current work demonstrates that strategic side group engineering could be a promising approach to developing high-performance all organic phosphors as well as improving the properties of existing phosphors.
在本工作中，我们报道了基于烷氧基取代联苯甲酰的全有机室温磷光体，其表现出结晶诱导磷光（CIP）。制备了九种具有不同烷基长度（OCH: = 8 - 16）的目标化合物，并研究了烷基侧链长度对磷光性能的影响，与对甲氧基苯偶姻进行了比较。结果发现，随着烷基长度增加至壬氧基（BZL - OC9），磷光量子产率和寿命均随之增加。碳原子数进一步增加会导致磷光性能恶化，这是由于侧链构象自由度增大所致。BZL - OC9实现了高达70%的惊人量子产率。一个有前景的发现是，相对于对甲氧基苯偶姻，量子产率的增加伴随着寿命的增加，而这在历史上一直具有挑战性。单晶X射线衍射结合紫外 - 可见光谱表明，对甲氧基苯偶姻中观察到更高水平的分子间π - π相互作用，而对于BZL - OC8则发现更多的烷基相互作用且分子间π轨道重叠较少。结果，BZL - OC8实现了分子刚性化且磷光猝灭较少，从而性能得到增强。对二氯甲烷溶液作为甲醇（不良溶剂）含量函数的沉淀研究证明，BZL - OC体系的发射确实是聚集诱导的。当前工作表明，战略性的侧链基团工程可能是开发高性能全有机磷光体以及改善现有磷光体性能的一种有前景的方法。
