Thermochemically Stable Liquid-Crystalline Gold(I) Complexes Showing Enhanced Room Temperature Phosphorescence

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.

Aggregation-Enhanced Room-Temperature Phosphorescence from Au(I) Complexes Bearing Mesogenic Biphenylethynyl Ligands

“…Au-Au (aurophilic) interactions play an important role in inducing efficient luminescence from aggregates. This interaction is expressed when the distance between neighboring gold atoms falls in the range of 2.8-3.6 Å [3][4][5][6][7][8][9][10][11][12][13]. Since the emission from gold(I) complexes originate mostly from aggregates, their photophysical properties, such as emission color and intensity, are highly sensitive to changes in the aggregated structure.…”

Stimuli-Sensitive Aggregation-Induced Emission of Organogelators Containing Mesogenic Au(I) Complexes

“…We reported that these complexes formed dimers in the crystalline, LC and in isotropic phases owing to the strong interactions between the gold atoms of neighboring molecules, and that these dimers exhibited intense blue photoluminescence in the condensed phases. We observed that the luminescence properties, vis., luminescence color and intensity, of mesogenic Au complexes can be tuned by crystalline-LC and LC-isotropic phase transitions [11][12][13]38]. Namely, the mesogenic Au complexes showed both AIE behavior and a high sensitivity of the luminescence to their aggregated structure.…”

“…For instance, Au(I) complexes are known to be AIE-active materials and in the past decade, many groups have reported the AIE behavior of Au complexes [6][7][8][9][10]. In our previous studies, various Au complexes were found to show efficient room-temperature phosphorescence (RTP) with a quantum yield (Φ) of >50% in a crystalline state under ambient conditions [11][12][13][14]. Uniquely, in Au complexes, intermolecular interactions occur between Au atoms (aurophilic interactions) and their highly emissive properties in condensed phases have been attributed to these aurophilic interactions [10,[15][16][17][18][19]].…”

“…LCs are self-organized soft materials and the aggregated structures in LC phases can be easily controlled by external stimuli. Thus, several mesogenic Au complexes have been developed and their AIE and LC behaviors have been reported [11][12][13]. For example, AIE-active LC Au complexes with rod-like molecular structures (e.g., pentylisocyano 2-(4-(hexyloxy)phenyl)ethynylgold(I) (R6), Figure 1) have been studied [11].…”

Theoretical Investigation of Structural and Optoelectronic Properties of Ternary Acetylides A2MC2 (A = Li, Na, K) and (M = Te, Pb, Pt)

“…New materials with distinct structures and different properties have been updated by Głodek et al [14], Chan et al [15], Svahn et al [16], Marmol et al [17], and Sanchez-de-Diego et al [18], using multiple diagnostic techniques. On the other hand, there are many fields of use of these structures in several areas, as shown by Lankelma et al [19], Tian et al [20], Kuroda et al [21], Hau et al [22], and Zhou et al [23].…”