Characterization of novel pyridine‐derived N ‐heterocyclic silylenes via density functional theory perspective

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The effects of one and two fused six-membered heterocyclic rings on properties of novel singlet and triplet germylenes are studied, at density functional theory (DFT). The aim of the present work is to recognize the influence of nitrogen and phosphorus heteroatoms along with germylene center (GeC) on the stability, band gap, polarity, polarizability, electrophilicity, nucleophilicity, and charge. Irrespective of ortho or para organization, fusion of one pyridine and phosphinine ring causes more vibration frequency, stabilizing influence, and polarizability than two fused ones. The natural bond orbital (NBO) analysis of one fused germylenes displays covalent bonds with different powers between nitrogen and phosphorus heteroatoms with germylene center. They show different occupancy number for lone pair on the heteroatoms at ortho or para position. Also, because of dissimilar interactions of LP N8 !σ * C3-Ge16 , σ C3-Ge16 !σ * C2-N6 , LP P16 !σ * C3-Ge15 , and σ C3-Ge15 !σ * C2-P16 , they have different stabilization energy (E (2) ). There is a good consistency between singlet-triplet energy separation (ΔE s-t = E t -E s ) and E (2) values. The stability based on ΔE s-t and E (2) values of para-one fused germapyridines is more than the ortho-ones.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Substituent effects on the stability of N‐heterocyclic germylenes using density functional theory

Liu

Ahmadi

2021

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A theoretical evaluation for new fused remote N‐heterocyclic silylenes (RNHSis) using density functional theory

Ghaghaei

Babazadeh

Behmagham

et al. 2023

In this research, we compare and contrast the stability, polarity, polarizability, band gap, and global reactivity of singlet (s) and triplet (t) fused benzene N‐heterocyclic silylene (1‐s and 1‐t) along with five numbered congeners (2x‐s, and 2x‐t, x = CH2, SiH2, GeH2, NH, PH, AsH, O, S, and Se) at DFT (density functional theory). All singlet and triplet remote N‐heterocyclic silylenes (RNHSis) appear as minima showing positive force constant. Every singlet RNHSi emerges as ground state and exhibits more stability than its corresponding triplet RNHSi. In going from 1‐s to 2x‐s species, the thermodynamic and kinetic stability is increased, so that higher ΔEs‐t (= Et − Es) and higher band gap or ΔEHOMO–LUMO (=ELUMO − EHOMO) is considered for 2CH2‐s, 2NH‐s, and 2O‐s structures. In going from second row to forth row of every group in the periodic table, electronegativity of heteroatoms have pronounced effect on the stability, polarity, polarizability, and band gap of 2x‐s species. These silylenes show more stability than the synthesized silylene by Kira. Every 2x‐t silylene shows higher nucleophilicity (about 1.6 times) than its corresponding 2x‐s analogous. Every singlet RNHSi reveals lower nucleophilicity (N), higher electrophilicity (ω), chemical potential (μ), and global hardness (η) than its triplet congener. Furthermore, 2x‐s silylenes benefit from stabilization effect of two heteroatoms synchronously in the fused five‐membered ring via mesomeric effect and π donation from the lone pairs of heteroatom to the formally vacant 3p orbital of the silylenic center. Hence, we predict higher stability as well as lower global reactivity of RNHSis than Kira's silylene will make them creditable for the synthetic research.

Theoretical descriptions on novel heteroatoms analogs of Hammick silylenes using density functional theory

Moradian

2023

In this investigation, we have been compared and contrasted the substituent effects on stability using ΔΕs‐t (Et − Es), frequency, ΔΕHOMO‐LUMO (ELUMO − EHOMO), polarity, polarizability, Mülliken charge distribution and reactivity descriptors of the singlet and triplet Hammick silylenes derived from silapyridine‐4‐ylidene (1‐s, 2x‐s, 3x‐s and 1‐t, 2x‐t, 3x‐t; x = NH, PH, AsH, O, S, and Se) as well as the synthesized dialkylsilylenes by West (4‐s), Denk (5‐s), and Kira (6‐s). In all cases, singlet (s) silylenes appear as ground states, exhibiting more stability than their corresponding triplet (t) states. All the above s and t silylenes appear as minima on their energy surfaces showing the positive force constant and the positive harmonic vibration frequency. Regardless of how orchestrated substituent groups in either “W” or “chair” position; the most stability is demonstrated by substitution of NH, and O groups in the fused pyrrole ring, while the least stability is considered by Kira's silylene. In contrast to previous report on the N‐Heterocyclic Hammick carbenes, silylenes, and germylenes (NHCs, NHSis, and NHGes) that size, type, orientation, and the number of fused rings pronounced effect on stability of the corresponding divalent species, here σ‐donor/π‐donor groups (such as PH, AsH, S, and Se) similar to σ‐acceptor/π‐donor groups (such as NH and O) stabilize their corresponding silylenes. Furthermore, the scrutinized singlet silylenes reveal lesser nucleophilicity (N), greater electrophilicity (ω), higher chemical potential (μ), higher global hardness (η), and lower global softness (S) than the analogous triplet silylenes. All singlet and triplet species show the maximum electronic charge (ΔNmax) with positive sign.