Singlet–triplet energy differences in divalent five membered cyclic conjugated Arduengo-type carbenes XC2HN2M (M = C, Si, Ge, Sn, and Pb; X = F, Cl, Br, and I)

Abstract

Singlet-triplet energy differences in Arduengo-type carbenes XC₂HN₂C compared and contrasted with their sila, germa, stana and plumba analogues; at B3LYP/6-311++G** level of theory. Free Gibbs energy differences between triplet (t) and singlet (s) states (ΔG(t–s)) change in the following order: plumbylenes > stannylenes > germylenes > silylenes > carbenes. The singlet states in XC₂HN₂C are generally more stable when the electron withdrawing groups such as–F was used at β-position. However, the singlet states in XC₂N₂HM (M = Si, Ge, Sn, and Pb) are generally more stable when the withdrawing groups such as–F was placed. The puckering energy is investigated for each the singlet and triplet states. The DFT calculations found the linear correlation to size of the group 14 divalent element (M), the ∠N–M–N angle, and the Δ(LUMO–HOMO) of XC₂HN₂M.