Theoretical insights of solvent effect on tautomerism, stability, and electronic properties of 6‐ketomethylphenanthridine

Abstract

In this manuscript, the influence of solvent on stability and electronic properties of enolimine, enaminone, and iminone forms of 6‐ketomethylphenanthridine is theoretically investigated using polarizable continuum model (PCM). Here, PCM is used during optimization of structures of tautomeric forms in solution. Water, ethanol, acetone, acetonitrile, chloroform, diethyl ether, dichloromethane, and dimethyl sulfoxide are chosen as solvent. The calculations are performed at M06‐2X/6‐311++G(d,p) level. In gas phase and in the solvents, the stability of tautomers increases as enaminone > enolimine > iminone. The topological properties of electron charge density are also studied for better understanding of stability of tautomers. It is observed that the stability of tautomers is diminished by increasing dielectric constant of solvent. Also, the increase in dielectric constant of solvent kinetically and thermodynamically facilitates the enolimine ⇌ enaminone tautomerization. To obtain more valuable information on stabilities of tautomers in water phase, the PCM calculations have also been performed with one water molecule. At M06‐2X/6‐311++G(d,p) level of theory, the stability of complexes is amplified as enaminone–water > iminone–water (V) > iminone–water (IV) > enolimine–water. The relationships between dielectric constant of solvent and some electronic properties of tautomers such as band gap, electron affinity, electrophilicity index, first ionization energy, electronic chemical potential, chemical softness, and hardness are also investigated.