In Silico Design of Fluorinated Fluorene Derivatives: A DFT Study on Structure–Property Relationships for OLED Applications

This study carries out a structural, electronic, and optical analysis of fluorene and its fluorinated derivatives, 9-Fluorofluorene (C₁₃H₉F) and 2-Fluorofluorene (C₁₃H₉F), applying Density Functional Theory (DFT) with the B3LYP/6-31G(d,p) functional featured in Gaussian 16. Results from geometry optimization show that the substitution of fluorine at the 9th and 2nd positions increases bond lengths slightly: 1.36 Å and 1.35 Å for C-F bond lengths while C-C bond lengths maintain at about 1.40 Å. The total energy for 9-Fluorofluorene was -297.45 kcal/mol and -296.87 kcal/mol for 2-Fluorofluorene compared to the parent fluorene with -295.56 kcal/mol, showing more enhanced stability. Analysis of the dipole moment showed that it rose from 0.78 D (for fluorene) to 1.25 D and 1.16 D for 9-Fluorofluorene and 2-Fluorofluorene. The UV-Vis absorption maxima were found to be 320 nm for fluorene, 295 nm for 9-Fluorofluorene, and 305 nm for 2-Fluorofluorene showing a red-shift in the absorption spectra. These results promise possible applications in optoelectronics due to improved stability, enhanced dipole moments, and red-shifted absorption properties of the fluorinated derivatives.