Controlling the solid-state luminescence of gold(I) N-heterocyclic carbene complexes through changes in the structure of molecular aggregates
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Thermally stable, solid-state luminescent organic materials are highly desired for the development of practical applications. Herein we synthesized new gold(I) complexes with N-heterocyclic carbene ligands, which have the ability to form strong metal-organic bond. Consequently, their thermochemical stability is enhanced at temperatures around 300 °C. Precise design of the molecular structure of the ligands, with a focus on ensuring low steric hindrance around Au atoms in order to limit disturbances to Au/Au interactions, provided a complex with a densely packed crystal with a shorter intermolecular Au–Au distance (3.17 Å) than the typical distance. In the solid state, this complex exhibited strong aurophilic interactions, which generated intense phosphorescence even in air at room temperature (quantum yield=16%) in spite of absence of any phosphorescence in solution. This behavior is characteristic for solid-state luminescence referred to as aggregation-controlled emission. Furthermore, the gold (I) complex displays capacity for mechano- and vapo-chromism—that is, the ability to change color reversibly in response to the application of external stimuli. We believe that the proposed design framework, which involves controlling thermal stability and luminescence property separately, provides a new opportunity for the development of practical applications using solid-state luminescent organic molecules.
KeywordsAu complex N-heterocyclic carbene phosphorescence mechanochromism aggregation-induced emission
This work was supported by the JSPS KAKENSHI (18K05265), JST Matching Planner Program (VP29117941122), JICA Collaboration Kick-starter Program (RU and IITH), and the Cooperative Research Program of the Network Joint Research Center for Materials and Devices (Tokyo Institute of Technology).
- 2.Ronda CR. Emission and excitation mechanisms of phosphors. In: Ronda CR, Ed. Luminescence: From Theory to Applications. Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA, 2008. 1–34Google Scholar
- 3.Birks JB. Photophysics of Aromatic Molecules. London: Wiley-Intersience, 1970Google Scholar
- 4(a).Luo J, Xie Z, Lam JWY, Cheng L, Tang BZ, Chen H, Qiu C, Kwok HS, Zhan X, Liu Y, Zhu D. Chem Commun, 2001, 1740–1741Google Scholar
- 17.Díez-González S, Ed. N–Heterocyclic Carbenes From Laboratory Curiosities to Efficient Synthetic Tools. London: RSC Publishing, 2010Google Scholar
- 20(a).Sheldrick GM. SHELXS-2014, Program for Crystal Structure Solution. Göttingen: University of Göttingen, 2014Google Scholar
- 24(a).Yuan WZ, Zhang Y, Tang BZ. Crystallization-induced phosphorescence for purely organic phosphors at room temperature and liquid crystals with aggregation-induced emission characteristics. In: Tang BZ, Qin A, Eds. Aggregation-Induced Emission: Applications. Hoboken: John Wiley & Sons, Ltd, 2013. 43–60CrossRefGoogle Scholar