Molecular and Aggregate Synergistic Engineering of Aggregation-Induced Emission Luminogens to Manipulate Optical/Electronic Properties for Efficient and Diversified Functions

The optical/electronic properties of organic luminescent
materials
can be regulated by molecular structure modification, which not only
requires sophisticated and time-consuming synthesis but also is unable
to accurately afford the optical properties of materials in the aggregate
state. Herein, a facile strategy of molecular and aggregate synergistic
engineering is proposed to manipulate the optical/electronic properties
of a luminogen, ACIK, in the solid state for efficient and diversified
functions. ACIK is facilely synthesized and exhibits three polymorphic
states (ACIK-Y, ACIK-R, and ACIK-N) with a large emission difference
of 102 nm from yellow to near-infrared (NIR). Their structure–property
relationships were investigated by crystallographic analyses and computational
studies. ACIK-Y, with the most twisted structure, exhibits an intriguing
color-tuned fluorescence between yellow and NIR in the solid state
in response to multiple stimuli. Shuttle-like ACIK-R microcrystals
exhibit an optical waveguide property with a low optical loss coefficient
of 19 dB mm–1. ACIK dots display bright NIR-I emission,
large Stokes shift, and strong NIR-II two-photon absorption. ACIK
dots show specific lipid droplets-targeting capability and can be
successfully applied for two-photon fluorescence imaging of mouse
brain vasculature with deep penetration and high spatial resolution.
This study will inspire more insights in developing advanced optical/electronic
materials based on a single chromophore for practical applications.