Singlet–Triplet Energy Gaps of Divalent Five-Membered Fused Rings C₈H₆M (M = C, SI, GE, SN, PB)

Abstract

Energy differences, ΔX_s–t (X = E, H and G) [ΔX_{s –t} = X(singlet) − X(triplet)] between singlet (s) and triplet (t) states of C₈H₆M (M = C, Si, Ge, Sn and Pb) were calculated at B3LYP/6–311+G*. The DFT calculations indicated that the ΔG_s–t between singlet (s) and triplet (t) states of C₈H₆M increased from M = C to M = Pb. The ΔG_s–t of C₈H₆M was compared with its analogues, C₄H₄M, through replacement of heavy atoms from M = C to M = Pb. Configurations of the electrons in orbitals (σ² or π²) for the singlet state of C₈H₆M are discussed.

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GRAPHICAL ABSTRACT

Keywords:

• Carbene
• fused divalent five-membered
• singlet–triplet energy gap