Abstract
Gold(I) complexes are some of the most attractive materials for generating aggregation-induced emission (AIE), enabling the realization of novel light-emitting applications such as chemo-sensors, bio-sensors, cell imaging, and organic light-emitting diodes (OLEDs). In this study, we propose a rational design of luminescent gold complexes to achieve both high thermochemical stability and intense room temperature phosphorescence, which are desirable features in practical luminescent applications. Here, a series of gold(I) complexes with ligands of N-heterocyclic carbene (NHC) derivatives and/or acetylide were synthesized. Detailed characterization revealed that the incorporation of NHC ligands could increase the molecular thermochemical stability, as the decomposition temperature was increased to ~300 °C. We demonstrate that incorporation of both NHC and acetylide ligands enables us to generate gold(I) complexes exhibiting both high thermochemical stability and high room-temperature phosphorescence quantum yield (>40%) under ambient conditions. Furthermore, we modified the length of alkoxy chains at ligands, and succeeded in synthesizing a liquid crystalline gold(I) complex while maintaining the relatively high thermochemical stability and quantum yield.
Highlights
Nanolights, consisting of organic or inorganic compounds with a size of a few nanometers, enable the emission of bright light, and are attracting growing interest in the fields of bio-imaging, sensing, energy harvesting, and displays [1]
We discuss the thermodynamic behavior and photophysical properties of the new complex 3 by comparing them with the previously reported complexes 1 and 2. We found that both thermochemical stability and luminescence efficiency can be enhanced by combining acetylide and N-heterocyclic carbene (NHC) ligands in gold(I)
The luminescence band at 600 nm observed only for 2a is due to the intermolecular Au–Au interaction, and are assigned to a metal–metal-to-ligand charge transfer (MMLCT)
Summary
Nanolights, consisting of organic or inorganic compounds with a size of a few nanometers, enable the emission of bright light, and are attracting growing interest in the fields of bio-imaging, sensing, energy harvesting, and displays [1]. The toxicity of the components used to prepare quantum dots (e.g., cadmium) limits their potential applications. To overcome this issue, various approaches and designs have been proposed [3,4]. Pioneering research to address this challenge was performed in 2001 by the group of Tang [5,6,7], in which they proposed the concept of designing molecules with unique twisted shapes, such as tetraphenylethene, which restrict intramolecular interactions; these molecules strongly emit light in Crystals 2019, 9, 227; doi:10.3390/cryst9050227 www.mdpi.com/journal/crystals
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