On UV–Vis spectra and structure of the anticancer drug camptothecin in solutions

UV–Vis spectra of camptothecin (CPT) in toluene, acetone, ethanol, acetonitrile, dimethylsulfoxide and aqueous solutions are investigated by UV–Vis spectroscopy and DFT calculations. The structures of CPT and its π-dimer have been optimized using B3LYP and B97D functionals with cc-pVDZ basis sets. Solvent effects were estimated using the Integral Equation Formalism Polarizable Continuum Model. Electron transitions in the studied systems were evaluated by TD-DFT treatment. Whereas the strong peak at the highest wavelength corresponds to the CPT monomer, the existence of the blue shifted one may be explained by its π-dimers formation instead of CPT hydrogen bonding with water molecules.