Density functional theory (DFT) conformational analysis was carried out on the potential energy hypersurface (PEHS) of the carbazole-containing molecular fragment, S-4-(2-hydroxypropoxy)-carbazol, of the chiral cardiovascular drug molecule carvedilol, (1-(9H-carbazol-4-yloxy)-3-[2-(2-methoxyphenoxy)ethylamino]-2-propanol). The PEHS was computed in vacuum, chloroform, ethanol, DMSO, and water at the B3LYP/6-31G(d) level of theory. The carbazole ring system was confirmed to be planar, and the resultant PEHS in vacuum contained 19 converged minima, of which the global minima possessed a conformation with Χ1, Χ2, and Χ3 in the anti position and Χ10 in the g position. Conformer stability for the S-4-(2-hydroxypropoxy)carbazol PEHS was influenced by intramolecular hydrogen bonding. Tomasi PCM reaction-field calculations revealed that the lowest SCF energies, relative conformer energies, and solvation free energies (ΔGsolvation) for the S-4-(2-hydroxypropoxy)carbazol PEHS were in protic solvents, ethanol and water, because of the larger hydrogen bond donor values of these solvents, which aid in stabilization of the dipole moment created by the carbazole ring system and the oxygen and nitrogen atoms. However, solvent effects contributed most significantly to the stabilization of S-4-(2-hydroxypropoxy)carbazol conformers that contained no internal hydrogen bonding, whereas solvent effects were not as important for conformers that contained intramolecular hydrogen bonding.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry