SINGLET-TRIPLET GAP STUDIES ON ARYL-CYCLOPENTADIENYLIDENES: INDIRECT ELECTRONIC EFFECTS

Energy gaps, Delta XS-t (X = E, H and G) (Delta XS-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.