Stabilization of novel N‐heterocyclic germylenes: A computational perspective

Abstract

AbstractIn this theoretical survey, N‐heterocyclic Germylenes (NHGes; 1–13) are compared and contrasted at DFT. All singlet (s) and triplet (t) states of NHGes turn out as minima for showing no negative force constant on their energy surfaces. Yet, only s states appear as global minima. From thermodynamic view point, the scrutinized NHGes show singlet‐triplet energy gap (ΔEs–t) larger than that of VI and VII germylenes, in the range of 51.45–60.37 versus 49.72 and 42.83 kcal/mol, respectively. In addition, all species are found less stable than NHGes synthesized by Veith (V) and more stable than the NHGes synthesized by Herrmann (VI) and Driess (VII) and so except for 9s–13s structures, reminder singlet divalent species have minimum vibrational frequencies (υmin) more than 100 cm−1. From kinetic view point, the ΔEHOMO–LUMO (band gap) of all singlet NHGes under study is higher than that of Driess's germylene. Henceforth, 1s–8s structures as stable molecules satisfy the identified conditions by Hoffmann, Schleyer, and Schaefer. Dimer of the singlet 1H‐4‐germapyridine‐4‐ylidene (1s), is found 11.44 kcal/mol less thermodynamically stable than its corresponding aromatic monomer. Endothermicity of head‐to‐head dimerization indicates that the reaction is unfavorable for 1, just as 8, while exothermicity shows that head‐to‐head dimerization is favorable for the others especially 9. This survey indicates the substitution effects of fused rings on thermodynamic and kinetic stabilities of NHGes hoping to prompt the experimental attentions toward them.