Highly Luminescent Liquid Crystals in Aggregation Based on Platinum(II) Complexes

Abstract

Luminescent liquid crystals (LLCs) attract considerable attention because of their broad applications in displays, chemosensors, and anti-counterfeiting. However, it remains challenging to achieve a high luminescence efficiency in LCs because of the common aggregation-caused quenching effect. Herein, we demonstrate a facile approach to designing LLCs with a high quantum yield up to 88% by deliberately tuning the aggregation behavior of platinum(II) complexes with alkoxy chains (C n H 2n+1 O−). LLCs in hexagonal columnar and rectangular columnar phases are achieved when n = 12 and 16, respectively, as revealed by one-dimensional wide-angle X-ray diffraction and small-angle X-ray scattering. These LLCs are able to not only exhibit strong emission at elevated temperatures but also show attractive reversible vapochromism upon alternative CH 2 Cl 2 and EtOH fuming, which imparts added functions and promises technological utility.

Perylene Bisimide-Based Luminescent Liquid Crystals with Tunable Solid-State Light Emission

“…Luminescent LC materials have recently received increasing attention, and they are usually designed by the incorporation of aggregation-induced (enhanced) emission active mesogens with twisted molecular conformations. − However, these LCs are not able to maintain their high efficiency luminescence at elevated temperatures, because the intense molecular motions induced by high temperatures contrast the mechanism of aggregation-induced emission in which intramolecular motions are strongly restricted in the aggregation state. , In our case, the conventional planar PBI-based luminescent LCs may lead to particular temperature responsiveness such as high-temperature luminescence. In addition, thermotropic LCs usually show strong dependence on temperatures, and a temperature-induced small molecular packing difference may lead to a large luminescence variation. ,− As the two supramolecular complex isomers exhibited significantly different thermotropic properties and assembled LC structures, we then investigated the possible temperature impact on their luminescence performance.…”

“…Perylene bisimides (PBIs) have received considerable attention for their excellent chemical/thermal stability, facile molecular design, and outstanding optical and electronic properties, which are of paramount importance in their applications as various optoelectronic devices. − Incorporation of PBIs in liquid crystals (LCs) beautifully demonstrates their general organization principle , and facilitates better processability than that of highly crystalline materials due to their dynamic reorganization ability. − In general, the large planar aromatic core of PBI tends to π–π-stack cofacially into discotic columnar LCs, which has led to their implementation in semiconductor-related devices. ,,− Despite the fluorescence quantum yield (Φ F ) of PBIs ranging up to unity in dilute solutions, almost all PBI-based LCs are nonfluorescent in the solid state due to their close π–π stacking, which provides a pathway for nonradiative decay to quench the emission. − Conversely, the advantageous combination of intrinsic light emission and unique self-organization properties of luminescent LCs − has facilitated advanced applications such as anisotropic displays, polarized emissions, − and multichromic fluorescence materials. − Thus, it is of significance but remains a challenge to overcome the prevailing fluorescence quenching pathways for constructing PBI-based luminescent LC materials.…”

Unveiling the Role of Hydrogen Bonds in Luminescent N‐Annulated Perylene Liquid Crystals

“…No significant color changes were observed by application of mechanical force (shearing). [ 4 , 8 , 16 ] However, the thin films of 1 and 2 exhibited the reversible emission change upon exposure to vapors of organic solvents such as CHCl 3 , THF, hexane or toluene (Figures 4 c and S17–S19),[ 17 , 18 ] while thin films of 3 and 4 showed no significant changes (Figures S20 and S21). In particular, the thin film of 2 shows (under exposure to 365 nm light) an enhancement of the emission and a concomitant color change from yellow to green when exposed to CHCl 3 vapors (Figure 4 c).…”

Chromic Platinum Complexes Containing Multidentate Ligands

“…Other tridentate ligands that have been used in vapochromic complexes include 2,6‐bis(benzimidazol‐2’‐yl)pyridine (bzimpy), [65,66] 2,6‐bis(1,2,3‐triazol‐4‐yl)pyridine (btapy), [67] and 2,6‐bis(1,2,4‐triazol‐4‐yl)pyridine [68] derivatives. In 2004, Grove et al.…”