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

Abstract

Thermal energy gaps, ΔEs–t; enthalpy gaps, ΔHs–t; Gibbs free energy gaps, ΔGs–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 ΔGs–t and electron withdrawing substituents (G = –F, –Cl, –Br, –CF3 and –NO2) lead to increase the ΔGs–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.