Palladium catalyzed carbon-carbon bond formation on tunable quinolines with DFT study

The synthesis of new quinoline fluorophores was accomplished through a meticulous four-step molecular assembly utilizing Suzuki and acid-amine cross-coupling reactions. The integrity of each fluorophore was rigorously confirmed via comprehensive spectroscopic analyses, including 1H and 13C NMR, DEPT-135, H-H COSY, HSQC NMR and HRMS techniques. Subsequently, the absorbance and emission spectra of the newly synthesized fluorophores were thoroughly investigated. Notably, these fluorophores displayed impressive characteristics, with high intensity and significant molar extinction coefficients, along with Stokes shifts ranging from 0.5052 x 104 to 0.6234 x 104 in acetonitrile (ACN) solvent. Absorbance spectra were found to confine within the 320-360 nm range, while emission spectra were consistently observed within the 380-450 nm range upon excitation at 350 nm. The electronic structure of the molecules was elucidated using techniques such as Density Functional Theory (DFT) and Molecular Electrostatic Potential (MEP) mapping. Additionally, the calculated global reactivity parameters provided valuable insights. In particular, compound 8b exhibited a distinctly larger energy gap compared to other fluorophores, demonstrating its exceptional properties. The comparison between experimental and theoretical UV-Vis spectra also showcased the remarkable consistency and quality of the synthesized fluorophores, highlighting the significant potential of this work in the field of fluorophore development.