Singlet-triplet gap studies on aryl-cyclopentadienylidenes: indirect electronic effects

Abstract

Energy gaps, ΔX_S–t (X = E, H and G) (∆X_s-t = X_(singlet)-X_(triplet)) between singlet (s) and triplet (t) states of aryl substituted cyclopentadienylidenes, Ar-C₄H₃C, were calculated at B3LYP/6-311++G**. Electron donating substituents (G = -NH₂, -OH, -CH₃, -F, -Cl and -Br) at phenyl group cause to increase and electron withdrawing substituents (G = -CF₃ and -NO₂) lead to decrease the singlet-triplet energy gaps of Ar-C₄H₃C. The results of the singlet-triplet gap calculations were fully supported by HOMO-LUMO gaps.

KEY WORDS: Carbene, Cyclopentadienylidenes, Singlet-triplet gap, Electronic effects

Bull. Chem. Soc. Ethiop. 2010, 24(2), 311-314.