Investigating functional performance and substituent effect in modelling molecular structure, UV-visible spectra, and optical properties of D-π-A conjugated organic dye molecules: a DFT and TD-DFT study

The molecular structure, UV-visible spectra, and optical properties of D-π-A conjugated organic dye molecules (Disperse Red 1 (DR1) Disperse 73 (DR73)) were analyzed using density functional theory (DFT) time-dependent (TD-DFT) compared with azobenzene molecule to study the effect donor acceptor substituents on properties. performance DFT functionals is investigated B3LYP hybrid three long-range corrected (CAM-B3LYP, LC-ω PBE, ω B97XD) in conjunction 6-31G(d,p) basis set. Using TD-DFT, we calculate vertical excitation energies transition dipole moment values for 100 excited states. These further utilized frequency dependent polarizability under sum-over-states (SOS) formalism refractive index these systems. We observe that DR1 molecules, B97XD predicted wavelengths corresponding peak absorbance closest experimental results, while DR73 molecule, gave better prediction. Large response also observed (DR1 DR73) comparison parent structure due charge transfer between groups. For αxx component dominates contrast where αyy dominates. HOMO → LUMO during contributes simulated spectra. high selected suggests are promising candidates tailor-made photonic optoelectronic device development.