Comparative Investigation of the Stabilities of Indene and Isoindene and the Their Heteroanalogs (N,O,S) Using Computational Methods

GRAPHICAL ABSTRACT

Abstract

Indene and isoindene and their heteroanalogs (N,O,S) were inspected in the gas phase and three solvents (heptane, acetonitrile, and water) and in the presence of water as an explicit solvent from point of views of thermodynamic, NBO and NMR studies. These compounds can be considered in two classes: benzo[b] and benzo[c] isomers. The calculations were performed by the Gaussian 03 program at the B3LYP\6-311++G** level of theory. In all cases and conditions, the absolute values of Gibbs free energies for benzo[c] isomers are smaller than the benzo[b] isomers, and also for each isomer, the absolute values of these energies increase with increasing value of the dielectric constant. Also, in all conditions, indole and isoindole have the maximum values for resonance energy of LP(X) → π* and the maximum diatropic ring currents due to their aromaticity.

Keywords:

• Fused-ring heterocycles
• explicit solvent
• NBO
• DFT
• ring current