Selective synthesis, structural studies and antitumor evaluation of some novel unsymmetrical 1-hetaryl-4-(2-chloroquinolin-3-yl)azines

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A series of novel unsymmetrical 1-hetaryl-4-(2-chloroquinolin-3-yl) azines 4–9 was selectively synthesized in a three-step procedure starting from acetanilide (1). The molecular structures of 4–9 were established by elemental analyses, spectral data, hybrid density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. Molecular conformation analysis for compounds 4–9, performed using DFT calculations utilizing the energy functional 3-Parameter (Exchange), Lee, Yang and Parr (B3LYP) and the full-electron basis set Density Gauss double-zeta with polarization functions (DGDZVP), on the synthesized azines considering the torsion angles (θ1, θ2, θ3) revealed 8 plausible conformers for each compound. Electronic and thermodynamic properties including the dipole moment and the thermodynamic energy values of the Frontier occupied and virtual molecular orbitals, HOMO and LUMO, respectively, were calculated for the most stable conformer for each compound. Furthermore, TD-DFT calculations coupled with the polarizable conductor calculation model (PCM), performed on the most stable conformers in DMF to account for the solvent effect, revealed that the optical properties including λmax and oscillator strength performed on the most stable conformers were in excellent agreement with the experimental λmax and molar extinction coefficient, which clearly validate the most stable molecular conformers identified for compounds 4–9. Comparison of the biological results to the calculated electronic and thermodynamic properties showed that the cytotoxicity is dependent on the low-lying ELUMO because compound 8 has the lowest ELUMO value and exhibited the greatest antitumor activity.