Computational Design, Synthesis, and Structure Property Evaluation of 1,3-Thiazole-Based Color-Tunable Multi-heterocyclic Small Organic Fluorophores as Multifunctional Molecular Materials.

Probing the chemical space of luminescent organic materials built on novel cores is highly imperative for its potential to expand the horizons of advanced functional materials. Small organic fluorophores possessing therapeutic traits can contribute to theranostics. We coupled computational and classical synthetic chemistry strategies for the rational design of 5-(hetero-2-yl)-1,3-thiazoles as color-tunable fluorophore core. With the aid of DFT and TD-DFT, we prove that the multi-heterocyclic system is built on a thiazole-het core with three inherent tunable sites on thiazole (C2, C4, and C5) capable of accommodating a panoply of substituents as a multifunctional molecular materials' platform. This de novo design offered unprecedented freedom to control strength and direction of charge transfer by varying donor-acceptor fragments. A 30-member fluorophore library built on thiazole-thiophene/furan core was accomplished using commercial reagents by a simple [4 + 1] synthesis. Structure-photophysical property studies revealed large Stokes shift, positive solvatochromism, acidochromism, and color tunability in different solvents and were rationalized using computational calculations. In vitro studies indicated 1a to be active against HL-60 cell lines, suggesting the possibility of expanding the core for theranostics. The lower values of computed hole reorganization energies indicated their potential as hole transporting materials in optoelectronics and widen the scope of these molecules as advanced functional materials.