Investigation of Thermodynamic Stability of para-Phenylthiophen Derivatives using G4 Theory

In the current work, the standard molar enthalpies of formation , ∆H_f^°, of para-position substituted phenylthiophene (PT) derivatives are computed using the quantum chemistry composite method (G4) at 298.15 K. The results obtained are carried out based on the substituent effect on the electronic, structural, and energetic properties of the studied molecules in gas-phase and acetonitrile media. In the atomization reaction route, the calculated values of ∆H_f^° for these compounds can be successfully associated with the substituent characteristics. The electron-withdrawing substituents increase the both ∆H_f^° and ionization potential (IP), while electron-donating ones cause a vice versa effect. In comparison with gas-phase, acetonitrile solvent satisfies the substituent effect on all calculated results. Moreover, both the calculated ∆H_f^° and IP values for substituted PT indicate a linear dependency on the energy of the highest occupied molecular orbital (HOMO) of studied molecules in two different environments.