Singlet-Triplet Splitting of Divalent Five-Membered Fused Rings C12H8M (M = C, Si, Ge, Sn, and Pb): Application in Nanocomplex Synthesis

Energy differences, Delta Xs-t (X = E, H, and G) (Delta Xs-t = X(singlet) - X(triplet)) between singlet (s) and triplet (t) states of C12H8M were calculated at B3LYP/6-311+G*. The DFT calculations indicated that the Delta G(s-t) between singlet (s) and triplet (t) states of C12H8M were increased from M = C to M = Pb. The.Gs-t of C12H8M was compared with its analogue C4H4M through replacement of heavy atoms from M = C to M = Pb. Configurations of the electrons in orbitals (sigma(2) or pi(2)) for the singlet state of C12H8M were discussed.