CF 3 -Pyridyl-Substituted Hetero-and Homocyclic Conjugated Molecules: From Non-Emissive to Highly Emissive through Core Engineering

Abstract

Herein, we report the synthesis of six CF 3 -pyridyl-substituted aromatics via Suzuki-Miyaura cross-coupling, incorporating electronically diverse heterocyclic (pyrazine, benzothiadiazole) and homocyclic (chrysene, anthracene, pyrene, perylene) cores to systematically probe structure-property relationships. UV-Vis absorption, steady-state and time-resolved photoluminescence, electrochemical measurements, and quantum chemical calculations demonstrate that the homocyclic derivatives exhibit long fluorescence lifetimes (τ), high photoluminescence quantum yields (ɸ PL ), large dipole moment changes (Δμ), optimally aligned frontier energy levels, and backbone-delocalized charge redistribution. Among these, anthracene-based compound (H-An) shows longest τ and highest ɸ PL with strongly suppressed non-radiative decay, pyrene derivative (H-Py) displays the largest Δμ, while the perylene analogue (H-Per) demonstrate red-shifted absorption, computed high light-harvesting efficiency, minimal exciton binding energy, and the lowest hole and electron reorganization energies, highlighting their potential as bright emitter or absorber for optoelectronic applications. In contrast, the heterocyclic compounds (H-Pz and H-BTD) are weakly emissive or nearly non-emissive, indicative of dominant non-radiative relaxation pathways. Density functional and time-dependent DFT calculations reproduce the experimental trends, underscoring that strategic core engineering within the CF 3 -pyridyl framework is an effective approach for tuning optical, charge-transport, and emissive properties in organic optoelectronic materials.