Abstract
Calculated geometrical parameters in the gas phase and solvents for 8-hydroxy-1-naphthaldehyde (8H1N) were carried out using density functional theory (DFT) at the 6-311++G(d,p) level, and the Time Dependent-DFT/6-311++G(d,p) method was used for the excited state calculations. 8H1N is found to exist in two main conforms, the cis-cis conformer (where the dihedral angels C3C2-OH is 0 degrees, C3C8-CO is 0 degrees) was found to be more stable than the trans-trans form (where the dihedral angels C3C2-OH is 180 degrees, C3C8 -CO is 180.0 degrees) by about 6.47 kcal/mol. The possibility of intramolecular hydrogen bonding between the hydroxyl (OH) and aldehyde (CHO) moieties is predicted. The hydrogen bond becomes stronger in polar solvents and in the excited state. Energies of 8H1N-one water molecule complexes are calculated using the DFT-D3 level of theory and results indicate that at least one solvent molecule is required to assist the proton transfer process.