Guest‐Induced Activation of Multicolor Photoluminescence in Naphthalene Bisimide Liquid Crystals

TL;DR

This paper introduces a new method to control the color and lifetime of light emission in liquid crystals using guest molecules, enabling a wide range of applications in optical technologies.

Contribution

A supramolecular strategy is introduced to activate and tune photoluminescence in naphthalene bisimide liquid crystals using electron-rich guests.

Findings

Embedding electron-rich guests in naphthalene bisimide LCs enables tunable emission from visible to near-infrared (511–685 nm).

Co-assembling two NBI hosts with one guest allows dual emission of green and red fluorescence and TADF.

The approach combines tunable photophysical properties with processability for optical encoding and security labeling.

Abstract

Achieving color‐ and lifetime‐tunable emission in processable materials remains challenging, as most of the available advanced materials systems exist only in impractical solutions or hard‐to‐process crystals. Liquid crystals (LCs) represent a promising platform due to their processability, though previous work has mainly controlled emission color by external fluorophore doping. In this work, we present a supramolecular strategy to activate and tune both photoluminescence (PL) color and lifetime in naphthalene bisimide (NBI) LCs by embedding electron‐rich guests. The electron‐deficient NBIs form columnar hexagonal mesophases stabilized by nanosegregation of aromatic cores and aliphatic side chains, providing a suitable environment for charge‐transfer (CT) interactions. Incorporating electron‐rich polycyclic aromatics, carbazole derivatives, or square‐planar Pt(II) complexes yields emissive CT states with tunable emission from visible to near‐infrared (511–685 nm), covering short‐lived fluorescence to long‐lived delayed luminescence of coexisting thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP). Co‐assembling two complementary NBI hosts with one guest enables an energy‐transfer cascade that simultaneously supports green and red dual emission of fluorescence and TADF. This additive‐induced activation and host‐mixing approach greatly broadens the luminescence range accessible in LCs, combining tunable photophysical properties with intrinsic processability for next‐generation optical encoding and security labeling technologies.

Supramolecular host–guest design in naphthalene bisimide liquid crystals activates charge‐transfer emission and enables continuous tuning of color (511–685 nm) and lifetime, spanning prompt fluorescence, TADF, and RTP. Electron‐rich guests and Pt(II) complexes modulate emissive states, while co‐assembled NBI complexes create an energy‐transfer cascade for dual emission. The processable LC platform targets advanced optical encoding and security labeling.

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