DFT Study of Functionalized Benzoxazole-Based D-π-A Architectures: Influence of Ionic Fragments on Optical Properties...

This theoretical work investigates the linear (absorption and emission) and nonlinear (first hyperpolarizability and TPA) optical properties of donor-π-acceptor (D-π-A) molecular architectures based on functionalized benzoxazoles, with potential applications in optoelectronic technologies such as OLEDs and solar cells. Four π-conjugated compounds were studied in the gas phase and in polar (methanol) and nonpolar (toluene) solvents, employing DFT with the B3LYP and CAM-B3LYP functionals and the 6-311++G(d,p) basis set, as implemented in Gaussian and Dalton. The results reveal that the chemical environment induces spectral shifts and modulates the intensity of electronic transitions. In particular, the compound 2-((4-((5-nitro-2-oxo-1,3-benzoxazol-3(2H)-yl)amino)phenyl)methyl)-1,3-benzoxazole exhibited outstanding behavior in methanol, with a significant increase in dipole moment, polarizability, and first hyperpolarizability (static and dynamic at 1064 nm), reaching a TPA cross-section close to 150 GM. These findings highlight the key role of ionic substituents in tuning the optical response of π-conjugated systems and underscore their potential as functional materials for high-performance light-emitting and energy-conversion devices.