Tunable synaptic memory response using organic regioisomeric donor-acceptor-donor luminophore triads.

Modeling synaptic memory with small molecular compounds allows for replication of key features of biological learning and memory in a simplified, controllable, and tunable chemical system, where processes such as signal transmission, plasticity, and information storage can be realized without the complexity of the full biological networks. Aimed at probing the substitution effects on the molecular conjugation and optoelectronic and neuromorphic performance, here we report novel regioisomeric donor-acceptor-donor (DAD) fluorophores that are utilized for optoelectronic synaptic memory devices. The photophysical characterization revealed substitution-dependent solid-state luminescence across the visible spectrum and variation in lifetimes that are attributed to the combination of molecular packing and charge-transfer characteristics. Diffraction methods and theoretical calculations elucidated the structure-property relationships, highlighting the effect of regiochemistry on the π-π interactions and molecular orbitals. The materials display synaptic memory responses in two-terminal organic devices, demonstrating key neuromorphic functionalities such as paired-pulse facilitation and long-term potentiation. This study introduces design guidelines for multifunctional organic semiconductors by regioisomerism, with potential applications extending to solid-state lighting, sensing, memory devices, and bioinspired computing.