Spectral (FT-IR, NMR) Analyses, Molecular Structures, and Chemical Bonding of Two Hexahydroacridine-1,8(2H,5H)-dione Derivatives: A Comparative Quantum Chemical Study

A comparative study on two hexahydroacridine-1,8(2H,5H)-dione deriv-atives namely, 9,10-bis(4-fluorophenyl)-3,3,6,6-tetramethyl-3,4,-6,7,9,10-hexahy-droacridine-1,8(2H,5H)-dione (FTHD) and 10-(4-fluorophenyl)-3,3,6,6-tetramethyl-9-(3,4,5-trimethoxyphenyl)-3,4,6,-7,9,10-hexahyd-roacridine-1,8(2H,5H)-dione (FTMPHD) has been performed. H-1 and C-13 NMR spectra have been recorded in the CDCl3 solvent. The equilibrium geometries of FTHD and FTMPHD have been determined and analyzed at DFT level employing B3PW91/6-311++G (d,p) method. The vibrational spectra of both the molecules are calculated and compared with the experimental FT-IR spectra. H-1 and C-13 NMR spectra have been calculated by using the gauge-independent atomic orbital (GIAO) method. The calculated spectra have been found to be in good agreement with the experimental spectra. The quantum theory of atoms-in-molecule (QTAIM) approach is employed to study various intramolecular interactions within these molecules. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and the molecular electrostatic potential (MESP) surfaces have been constructed and analyzed. Various electronic as well as thermodynamic parameters have been reported.