ELECTRONIC EFFECTS AT α-POSITION OF DIVALENT FIVE-MEMBERED RING CARBENES: SINGLET-TRIPLET ENERGIES THROUGH DFT CALCULATIONS

Abstract

Thermal energy gaps, ΔE_s–t; enthalpy gaps, ΔH_s–t; Gibbs free energy gaps, ΔG_s–t, between singlet (s) and triplet (t) states of G–C₄H₃C (G = –NH₂, –OH, –CH₃, –F, –Cl, –Br, –H, –CF₃, –NO₂) were calculated at B3LYP/6-311++G** level of theory. DFT calculations indicated that electron donating substituents (G = –NH₂, –OH and –CH3) at α position cause to decrease ΔG_s–t and electron withdrawing substituents (G = –F, –Cl, –Br, –CF₃ and –NO₂) lead to increase the ΔG_s–t of G-C₄H₃C. Nuclear independent chemical shifts (NICS) calculations were carried out to determine the aromatic character.

KEY WORDS: DFT calculations, Electronic effects, Singlet-triplet energies, Carbene, Five-membered, NICS


Bull. Chem. Soc. Ethiop. 2009, 23(1), 151-155.