Estimating the stability and reactivity of acyclic and cyclic mono-heteroatom substituted germylenes: A density functional theory investigation

The effects of nitrogen substituent on stability (ΔΕ s-t ) of novel germylenes with one, two, and three germylene centers are compared and contrasted at B3LYP/6-311++G** level of theory. These singlet and triplet germylenes (1 s -18 s and 1 t -18 t , respectively) appear as minimum on its energy surface, and the order of their stability estimated by singlet (s)-triplet (t) energy difference10 > 12 > 14 > 5 > 4 > 18 > 13. Hence, every singlet germylene shows more stability than its corresponding triplet. Germylene 13 with the lowest stability (ΔE s-t = 4.31 kcal/mol) has the highest nucleophilicity (4.47 eV). Applying suitable isodesmic reactions, we show that the σ-acceptor nitrogen substituents stabilize not only the singlet but also the triplet states with their positive ΔE. The aim of the present work is to recognize the influence of nitrogen and germylene centers on the stability and band gap (ΔΕ HOMO-LUMO ), electrophilicity (ω), nucleophilicity (N), and etc. They can be used as accumulated multidentate ligands.

Section: Introductionmentioning

confidence: 99%

Estimating the stability and reactivity of novel bicyclic germylenes at density functional theory

Abedini

Kassaee

2021

“…The acid‐base theory has been scrutinized for many years. [ 1–4 ] The acidity and basicity of carbenes, [ 5–7 ] silylenes, [ 8–10 ] germylenes, [ 11,12 ] and stannylenes [ 13 ] have been studied at theoretical levels. In contrast, plumbylenes, especially their acyclic isomers, are less considered.…”

Section: Introductionmentioning

confidence: 99%

Predicting novel strong acids of plumbylene at theoretical levels

Mohebi

Kassaee

2020

We have reached at new acyclic plumbylenes which show high acidity, via B3LYP, Def2‐TZVP, MP2, and wB97XD functionals. Our scrutinized plumbylenes include dicyclopropaplumbylene (1), dicyclopentaplumbylene (2), dicycloheptaplumbylene (3), and their unsaturated analogs (1’‐3’, respectively). All scrutinized plumbylenes and their corresponding protonated forms, 1H(1’H)‐3H(3’H), appear as minima on their energy surfaces. The conductor‐like polarizable continuum model (CPCM) and integral equation formalism polarized continuum model (IEFPCM) are used to predict the pka values for electrophilic plumbylenes, 1(1’)‐3(3’), in chloroform and water. In most cases, plumbylenes turn out as strong acids for showing relatively high negative pka values. The acidity trend of plumbylenes (pka) appears consistent with their proton affinity (PA), electrophilicity (ω), nucleophilicity (N), Mulliken electronegativity ( ), absolute chemical hardness (ηabs), singlet‐triplet energy gap (ΔEs‐t), and highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gap (ΔEH‐L). Structure 1, with two cyclopropyl groups, turns out as the most acidic specie in chloroform and water.

Estimating the stability and reactivity of cyclic tetrahalo substituted germylenes: A density functional theory investigation

Koohi

2019

The largest unsaturated carbene, cyclonona-3,5,7-trienylidene (1 H ), emerges as a boat-shaped transition state (TS) for having a negative force constant (FC).Following the quest for stable germylenes (2 X , where X = H, F, Cl, Br, and I) with C 8 H 6 X 4 Ge: formula, the density functional theory (DFT) calculations are carried out to assay the substituent effect on their thermodynamic and kinetic possibilities. These singlet and triplet germylenes (2 X -S and 2 X -T , respectively) appear as boat-shaped minima without imaginary frequencies and the order of their stability estimated by singlet (S)-triplet (T) energy difference (ΔE S-T = E T − E S ) is 1 H < 2 H < 2 F < 2 Cl < 2 I < 2 Br . The purpose of the present work is to swiftly switch from T carbene to S germylenes through alteration of the substituents and assess the influence of different halogens on the stability and other properties. The 2 Br -S seems as the most stable species. From kinetic point of view, 2 Cl , 2 Br , and 2 I are more stable than some of synthesized germylenes. The stabilization of the S state is essential to stabilize germylenes. This can be achieved by σ-electron withdrawing and π-electron donating substituents, of which stabilizing effect can be further increased in the order of steric effect < positive hyperconjugation < negative hyperconjugation < mesomeric effect. Applying suitable isodesmic reactions, we show the π-donor/σ-acceptor halogen substituents stabilize not only the S but also the T states, and these groups stabilize 2 X -S more than 2 X -T .