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Construction of a Conjugation Systemwith Heteroatoms in Polymer MainChains
Published in Atsushi Nagai, Koji Takagi, Conjugated Objects, 2017
In general, the brilliant emissions of conjugated polymers disappearby condensation. This fact means that optical properties shouldbe lost in the solid or film states. These behaviors are calledconcentration quenching or aggregation-caused quenching (ACQ).On the contrary, it has been reported that some of compoundsshowed stronger emission in the aggregation states. Tang et al.firstly showed unique behaviors with tetraphenyl-substituted silolecompounds in 2001.11 Only when the compounds were suspendedin the poor solvent, the bright emission can be observed. Thisphenomenon is called aggregation-induced emission (AIE), andthe application for highly emissive solid materials is expected toovercome ACQ. In particular, since ACQ directly contributes to thedecreases of the device efficiency in the electroluminescent (EL)devices, the development of new AIE-active molecules is still ofgreat interest in the development of modern electric devices. Inthis section, we explain the recent progress of the molecular designand the development of AIE-active conjugated polymers based onorganoboron complexes.
Tin(IV) halide complexes with 5,7-dimethyl-8-quinolinol: structures, optical and thermal properties
Published in Journal of Coordination Chemistry, 2022
Kathleen Ngo, Boris Averkiev, Gordan Tyson Reeves, Andrew Wu, Daniel Wooseok Ki
After development of an organic light-emitting aluminum (Al) complex with 8-hydroxyquinoline [1], research in the area of metal complex phosphors, with a focus on cost-effective and efficient organic light-emitting devices with tunable optical and electrical properties, has advanced at a rapid pace [2–4]. Although rare earth metal-based complexes have shown great promise and are commercially available, they are expensive and in limited supply. For this reason, efficient rare-earth-free metal complexes have sought to replace rare earth elements [5–8]. Post-transition metal-based light emitting phosphors, such as those of Sn, Bi, Sb, and Pb, have been complexed with C-, O-, and N- donor ligands, and used as alternatives to rare earth-based phosphors [9–12]. Sn and Pb greatly enhanced phosphorescent emission by promoting triplet electronic transitions of the ligands [13]. As a ligand, 8-hydroxyquinoline has been quite versatile, used to complex with various metals as well as displaying tunable optical properties through substitution of functional groups [14, 15]. Tin complexes with hydroxyquinoline derivatives have demonstrated their potential for use in electroluminescence devices [12, 16]. Furthermore, tin complexes have shown interesting biological activities, such as antimicrobial and antifungal activity [17–19]. The discovery of aggregation-induced emission properties shifts the field of organic light emitting diodes (OLEDs) research by improving the quantum efficiency of OLEDs, which are constructed from the aggregate form of materials [20, 21]. This phenomenon occurs as a result of restriction of intramolecular rotation or vibration in the aggregate state, which is desirable in comparison to the more common aggregation caused quenching due to unfavorable π-π stacking in the aggregate state that quenches the molecule’s emission [22]. We recently reported the first tin(IV) fluoride complex exhibiting blue-shifted aggregation-induced emission enhancement [23].